graphical programming - Page 538

App crashes when adding array data to table cells

- by bassmandan

I am trying to create a table view that loads a number of tweets into the table (one per cell etc). I am using NSXMLParser to get the information and have got as far as creating an array with the selection of tweets that I want. However, when I try to add them to the table cells, the app crashes on the line: cell.textLabel.text = cellValue; An NSLog before this shows in the console that the app is getting the correct data, so I am a bit stumped as to why this isn't working. This is the block of code that appears to be having the problem: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]; } // Set up the cell... NSString *cellValue = [statuses objectAtIndex:indexPath.row]; NSLog(@"%@", cellValue); cell.textLabel.text = cellValue; return cell;} If it makes a difference, I am using ARC and the latest version of XCode. I'm still quite new to all this, so if I need to give some extra information, let me know. Thanks in advance. Edit: Backtrace gives the following: * thread #1: tid = 0x2003, 0x918a19c6 libsystem_kernel.dylib`__pthread_kill + 10, stop reason = signal SIGABRT frame #0: 0x918a19c6 libsystem_kernel.dylib`__pthread_kill + 10 frame #1: 0x9968ff78 libsystem_c.dylib`pthread_kill + 106 frame #2: 0x99680bdd libsystem_c.dylib`abort + 167 frame #3: 0x03c93e78 libc++abi.dylib`_Unwind_DeleteException frame #4: 0x03c9189e libc++abi.dylib`_ZL17default_terminatev + 34 frame #5: 0x0154df4b libobjc.A.dylib`_objc_terminate + 94 frame #6: 0x03c918de libc++abi.dylib`_ZL19safe_handler_callerPFvvE + 13 frame #7: 0x03c91946 libc++abi.dylib`std::terminate() + 23 frame #8: 0x03c92ab2 libc++abi.dylib`__cxa_throw + 110 frame #9: 0x0154de15 libobjc.A.dylib`objc_exception_throw + 311 frame #10: 0x013bdced CoreFoundation`-[NSObject doesNotRecognizeSelector:] + 253 frame #11: 0x01322f00 CoreFoundation`___forwarding___ + 432 frame #12: 0x01322ce2 CoreFoundation`_CF_forwarding_prep_0 + 50 frame #13: 0x0015168f UIKit`-[UILabel setText:] + 56 frame #14: 0x00003088 Twitter`-[TwitterViewController tableView:cellForRowAtIndexPath:] + 376 at TwitterViewController.m:131 frame #15: 0x000ace0f UIKit`-[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 494 frame #16: 0x000ad589 UIKit`-[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] + 69 frame #17: 0x00098dfd UIKit`-[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 1350 frame #18: 0x000a7851 UIKit`-[UITableView layoutSubviews] + 242 frame #19: 0x00052301 UIKit`-[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 145 frame #20: 0x013bde72 CoreFoundation`-[NSObject performSelector:withObject:] + 66 frame #21: 0x01d6692d QuartzCore`-[CALayer layoutSublayers] + 266 frame #22: 0x01d70827 QuartzCore`CA::Layer::layout_if_needed(CA::Transaction*) + 231 frame #23: 0x01cf6fa7 QuartzCore`CA::Context::commit_transaction(CA::Transaction*) + 377 frame #24: 0x01cf8ea6 QuartzCore`CA::Transaction::commit() + 374 frame #25: 0x01d8430c QuartzCore`+[CATransaction flush] + 52 frame #26: 0x000124c6 UIKit`-[UIApplication _reportAppLaunchFinished] + 39 frame #27: 0x00012bd6 UIKit`-[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 1324 frame #28: 0x00021743 UIKit`-[UIApplication handleEvent:withNewEvent:] + 1027 frame #29: 0x000221f8 UIKit`-[UIApplication sendEvent:] + 68 frame #30: 0x00015aa9 UIKit`_UIApplicationHandleEvent + 8196 frame #31: 0x012a6fa9 GraphicsServices`PurpleEventCallback + 1274 frame #32: 0x013901c5 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53 frame #33: 0x012f5022 CoreFoundation`__CFRunLoopDoSource1 + 146 frame #34: 0x012f390a CoreFoundation`__CFRunLoopRun + 2218 frame #35: 0x012f2db4 CoreFoundation`CFRunLoopRunSpecific + 212 frame #36: 0x012f2ccb CoreFoundation`CFRunLoopRunInMode + 123 frame #37: 0x000122a7 UIKit`-[UIApplication _run] + 576 frame #38: 0x00013a9b UIKit`UIApplicationMain + 1175 frame #39: 0x0000239d Twitter`main + 141 at main.m:16 frame #40: 0x00002305 Twitter`start + 53 Debugging console shows this: 2012-04-08 10:10:05.084 Twitter[25309:f803] ( { text = "Have you shared the Shakedown yet? http://t.co/WHrIC9w7"; }, { text = "For all you closet rocknrollas pencil in Sat 12th May The Rebirth of Rock n Roll Party. Haywire Saint @ The Good... http://t.co/OXHKlLIV"; }, { text = "4 weeks today: Vocal tracks will be getting recorded at The Premises Studios"; }, { text = "Rehearsal tonight in preparation to some big recording next month!"; }, { text = "haywire saint 'great taste.' Tune. \n\nhttp://t.co/GKmu5Lna http://t.co/0fii55Hw"; }, { text = "Meeting up with an old roadie for The Cure today. oh the stories...... http://t.co/UeUYccme"; }, { text = "Satisfying day of programming today.. Haywire Saint app coming along nicely with the custom music player ready to rock 'n' roll!"; }, { text = "Happy Friday Everyone!"; }, { text = "We had a great time at The Premises Studios yesterday. We'll be back there before long :D x"; }, { text = "I posted a new photo to Facebook http://t.co/73qAnCvk"; } ) 2012-04-08 10:10:05.093 Twitter[25309:f803] { text = "Have you shared the Shakedown yet? http://t.co/WHrIC9w7"; } 2012-04-08 10:10:05.094 Twitter[25309:f803] -[__NSCFDictionary isEqualToString:]: unrecognized selector sent to instance 0x6877a50 2012-04-08 10:10:05.096 Twitter[25309:f803] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFDictionary isEqualToString:]: unrecognized selector sent to instance 0x6877a50' *** First throw call stack: (0x13bc052 0x154dd0a 0x13bdced 0x1322f00 0x1322ce2 0x15168f 0x3088 0xace0f 0xad589 0x98dfd 0xa7851 0x52301 0x13bde72 0x1d6692d 0x1d70827 0x1cf6fa7 0x1cf8ea6 0x1d8430c 0x124c6 0x12bd6 0x21743 0x221f8 0x15aa9 0x12a6fa9 0x13901c5 0x12f5022 0x12f390a 0x12f2db4 0x12f2ccb 0x122a7 0x13a9b 0x239d 0x2305) terminate called throwing an exception2012-04-08 10:10:05.924 Twitter[25309:f803] -[__NSCFConstantString count]: unrecognized selector sent to instance 0x5b30

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I asked this yesterday, after the input given I'm still having trouble implementing..

- by Josh

I'm not sure how to fix this or what I did wrong, but whenever I enter in a value it just closes out the run prompt. So, seems I do have a problem somewhere in my coding. Whenever I run the program and input a variable, it always returns the same answer.."The content at location 76 is 0." On that note, someone told me that "I don't know, but I suspect that Program A incorrectly has a fixed address being branched to on instructions 10 and 11." - mctylr but I'm not sure how to fix that.. I'm trying to figure out how to incorporate this idea from R Samuel Klatchko.. I'm still not sure what I'm missing but I can't get it to work.. const int OP_LOAD = 3; const int OP_STORE = 4; const int OP_ADD = 5; ... const int OP_LOCATION_MULTIPLIER = 100; mem[0] = OP_LOAD * OP_LOCATION_MULTIPLIER + ...; mem[1] = OP_ADD * OP_LOCATION_MULTIPLIER + ...; operand = memory[ j ] % OP_LOCATION_MULTIPLIER; operation = memory[ j ] / OP_LOCATION_MULTIPLIER; I'm new to programming, I'm not the best, so I'm going for simplicity. Also this is an SML program. Anyway, this IS a homework assignment and I'm wanting a good grade on this. So I was looking for input and making sure this program will do what I'm hoping they are looking for. Anyway, here are the instructions: Write SML (Simpletron Machine language) programs to accomplish each of the following task: A) Use a sentinel-controlled loop to read positive number s and compute and print their sum. Terminate input when a neg number is entered. B) Use a counter-controlled loop to read seven numbers, some positive and some negative, and compute + print the avg. C) Read a series of numbers, and determine and print the largest number. The first number read indicates how many numbers should be processed. Without further a due, here is my program. All together. int main() { const int READ = 10; const int WRITE = 11; const int LOAD = 20; const int STORE = 21; const int ADD = 30; const int SUBTRACT = 31; const int DIVIDE = 32; const int MULTIPLY = 33; const int BRANCH = 40; const int BRANCHNEG = 41; const int BRANCHZERO = 41; const int HALT = 43; int mem[100] = {0}; //Making it 100, since simpletron contains a 100 word mem. int operation; //taking the rest of these variables straight out of the book seeing as how they were italisized. int operand; int accum = 0; // the special register is starting at 0 int j; // This is for part a, it will take in positive variables in a sent-controlled loop and compute + print their sum. Variables from example in text. memory [0] = 1010; memory [01] = 2009; memory [02] = 3008; memory [03] = 2109; memory [04] = 1109; memory [05] = 4300; memory [06] = 1009; j = 0; //Makes the variable j start at 0. while ( true ) { operand = memory[ j ]%100; // Finds the op codes from the limit on the memory (100) operation = memory[ j ]/100; //using a switch loop to set up the loops for the cases switch ( operation ){ case 10: //reads a variable into a word from loc. Enter in -1 to exit cout <<"\n Input a positive variable: "; cin >> memory[ operand ]; break; case 11: // takes a word from location cout << "\n\nThe content at location " << operand << "is " << memory[operand]; break; case 20:// loads accum = memory[ operand ]; break; case 21: //stores memory[ operand ] = accum; break; case 30: //adds accum += mem[operand]; break; case 31: // subtracts accum-= memory[ operand ]; break; case 32: //divides accum /=(memory[ operand ]); break; case 33: // multiplies accum*= memory [ operand ]; break; case 40: // Branches to location j = -1; break; case 41: //branches if acc. is < 0 if (accum < 0) j = 5; break; case 42: //branches if acc = 0 if (accum == 0) j = 5; break; case 43: // Program ends exit(0); break; } j++; } return 0; }

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JavaScript snippet that populates the table

- by kayn

I would like to write a JavaScript snippet that populates the table based on the selection, and not create several details panes and toggle their visibility. I tried implement this using the following code but its not working as desired,firstly,it only works with internet explorer under certain conditions and it just toggles visibility of detail panes;Below is my code; <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <HTML> <HEAD> </HEAD> <BODY onLoad="tblTB_0.style.display='';tblTB_1.style.display='none'; tblTB_2.style.display='none'; tblTB_3.style.display='none'"> <center> <table> <tr> <td> <H1> <align="left"> Candi Colledge of Computing <br/>Course Page </H1> </td> </tr> </table> </center> <hr> </br> <H2><P STYLE="color: blue">Honours Courses.</H2> <left> <p><a href="" onclick="tblTB_1.style.display=''; tblTB_2.style.display='none'; tblTB_3.style.display='none'"> Concurrent Programming</a> <br/> <a href="" onclick="tblTB_1.style.display='none';tblTB_2.style.display=''; tblTB_3.style.display='none'">Simulation of Networks</a><br/> <a href="" onclick="tblTB_1.style.display='none';tblTB_2.style.display='none'; tblTB_3.style.display=''">Advanced Computer Science Topics</a></p> <br> <table style="table-layout: fixed"; border=1> <colgroup> <col width="100px"><col width="150px"><col width="150px"> </colgroup> <tbody id="tblTB_0"> <tr> <td>Course Code</td> <td>Lecturer</td> <td>Hours/Week</td> <td>Credits</td> </tr> </tbody> <tbody id="tblTB_1"> <tr> <td>RW 714</td> <td>Dr. kate</td> <td>2 hrs</td> <td>15</td </tr> </tbody> <tbody id="tblTB_2"> <tr> <td>RW 742</td> <td>Prof. Broz</td> <td>4 hrs</td> <td>10</td> </tr> </tbody> <tbody id="tblTB_3"> <tr> <td>RW 716</td> <td>Consultant</td> <td>3 hrs</td> <td>12</td> </tr> </tbody> </table> </left> <br> </BODY> </HTML>

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SWIG & C/C++ Python API connected - SEGFAULT

- by user289637

Hello, my task is to create dual program. At the beginning I start C program that calls throught C/C++ API of Python some Python method. The called method after that call a function that is created with SWIG. I show you my sample also with backtrace from gdb after I am given Segmentation fault. main.c: #include <Python.h> #include <stdio.h> #include "utils.h" int main(int argc, char** argv) { printf("Calling from C !\n"); increment(); int i; for(i = 0; i < 11; ++i) { Py_Initialize(); PyObject *pname = PyString_FromString("py_function"); PyObject *module = PyImport_Import(pname); PyObject *dict = PyModule_GetDict(module); PyObject *func = PyDict_GetItemString(dict, "ink"); PyObject_CallObject(func, NULL); Py_DECREF(module); Py_DECREF(pname); printf("\tbefore finalize\n"); Py_Finalize(); printf("\tafter finalize\n"); } return 0; } utils.c #include <stdio.h> #include "utils.h" void increment(void) { printf("Incremention counter to: %u\n", ++counter); } py_function.py #!/usr/bin/python2.6 '''py_function.py - Python source designed to demonstrate the use of python embedding''' import utils def ink(): print 'I am gonna increment !' utils.increment() and last think is my Makefile & SWIG configure file Makefile: CC=gcc CFLAGS=-c -g -Wall -std=c99 all: main main: main.o utils.o utils_wrap.o $(CC) main.o utils.o -lpython2.6 -o sample swig -Wall -python -o utils_wrap.c utils.i $(CC) utils.o utils_wrap.o -shared -o _utils.so main.o: main.c $(CC) $(CFLAGS) main.c -I/usr/include/python2.6 -o main.o utils.o: utils.c utils.h $(CC) $(CFLAGS) -fPIC utils.c -o $@ utils_wrap.o: utils_wrap.c $(CC) -c -fPIC utils_wrap.c -I/usr/include/python2.6 -o $@ clean: rm -rf *.o The program is called by ./main and there is output: (gdb) run Starting program: /home/marxin/Programming/python2/sample [Thread debugging using libthread_db enabled] Calling from C ! Incremention counter to: 1 I am gonna increment ! Incremention counter to: 2 before finalize after finalize I am gonna increment ! Incremention counter to: 3 before finalize after finalize I am gonna increment ! Incremention counter to: 4 before finalize after finalize Program received signal SIGSEGV, Segmentation fault. 0xb7ed3e4e in PyObject_Malloc () from /usr/lib/libpython2.6.so.1.0 Backtrace: (gdb) backtrace #0 0xb7ed3e4e in PyObject_Malloc () from /usr/lib/libpython2.6.so.1.0 #1 0xb7ca2b2c in ?? () #2 0xb7f8dd40 in ?? () from /usr/lib/libpython2.6.so.1.0 #3 0xb7eb014c in ?? () from /usr/lib/libpython2.6.so.1.0 #4 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #5 0xb7f99820 in ?? () from /usr/lib/libpython2.6.so.1.0 #6 0x00000001 in ?? () #7 0xb7f8dd40 in ?? () from /usr/lib/libpython2.6.so.1.0 #8 0xb7f4f014 in _PyObject_GC_Malloc () from /usr/lib/libpython2.6.so.1.0 #9 0xb7f99820 in ?? () from /usr/lib/libpython2.6.so.1.0 #10 0xb7f4f104 in _PyObject_GC_NewVar () from /usr/lib/libpython2.6.so.1.0 #11 0xb7ee8760 in _PyType_Lookup () from /usr/lib/libpython2.6.so.1.0 #12 0xb7f99820 in ?? () from /usr/lib/libpython2.6.so.1.0 #13 0x00000001 in ?? () #14 0xb7f8dd40 in ?? () from /usr/lib/libpython2.6.so.1.0 #15 0xb7ef13ed in ?? () from /usr/lib/libpython2.6.so.1.0 #16 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #17 0x00000001 in ?? () #18 0xbfff0c34 in ?? () #19 0xb7e993c3 in ?? () from /usr/lib/libpython2.6.so.1.0 #20 0x00000001 in ?? () #21 0xbfff0c70 in ?? () #22 0xb7f99da0 in ?? () from /usr/lib/libpython2.6.so.1.0 #23 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #24 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #25 0x080a6b0c in ?? () #26 0x080a6b0c in ?? () #27 0xb7e99420 in PyObject_CallFunctionObjArgs () from /usr/lib/libpython2.6.so.1.0 #28 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #29 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #30 0x800e55eb in ?? () #31 0x080a6b0c in ?? () #32 0xb7e9958c in PyObject_IsSubclass () from /usr/lib/libpython2.6.so.1.0 #33 0xb7f8dd40 in ?? () from /usr/lib/libpython2.6.so.1.0 #34 0x080a9020 in ?? () #35 0xb7fb78f0 in PyFPE_counter () from /usr/lib/libpython2.6.so.1.0 #36 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #37 0x00000000 in ?? () Thanks for your help and advices, marxin

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Passing GLatLng from array to Google

- by E. Rose

Hello All, To preface this, I am a complete programming amateur so this may be quite easily solved. As is though, it is frustrating me to no end. Basically, I have a database of Venue Names with GLat and GLng (other stuff too) that I am pulling down to my website based on a geolocated search. The javascript that I have pulls in a formatted subset of the database, dumps the glat and glng into an array and is supposed to take those points and plot out several markers each with an info window containing the details behind each marker. For some reason, the marker geodata is not being populated and/or is not being passed. The array is declared using [] and will not work when normally declared using (). It only brings up a map with the first value in the array and goes blank if i try to manually input later entries. There is a large block of commented out code relating to directions generation. That code worked for some reason. If anyone can tell me what I am doing wrong in rewriting it to map the markers and not give directions, please tell me. Any help would be much appreciated. var letters = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z']; google.load("maps", "2", {"other_params":"sensor=true"}); var map function initialize(){ window.map = new google.maps.Map2(document.getElementById("map")); map.addControl(new GLargeMapControl()); } google.setOnLoadCallback(initialize); function getVenueResults(_zip, _num, _remove){ var rFlag = ''; if(_remove != null){ rFlag = "&removeId=" + _remove; } var url = 'ajax/getVenues.php?zip=' + _zip + "&num=" + _num + rFlag; new Ajax.Updater('resultsContainer', url, { onComplete: processResults }); } function processResults(){ window.map.clearOverlays(); var waypoints = []; var resultsList = $$('.resultWrapper'); var stepList = $$('.resultDirections'); for(i=0; i for(i=0; i<resultsList.length; i++){ var resultsElem = resultsList[i]; resultsElem.removeClassName('firstResult'); resultsElem.removeClassName('lastResult'); if(i == 0){ resultsElem.addClassName('firstResult'); } if(i == resultsList.length - 1){ resultsElem.addClassName('lastResult'); } var insertContent = '<div class="resultDirections" id="resultDirections' + i + '"></div>'; Element.insert(resultsElem, { bottom : insertContent }) var num = resultsElem.getElementsByClassName('numHolder'); num[0].innerHTML = '<b>' + letters[i] + ".</b> "; var geolat = resultsElem.getElementsByClassName('geolat')[0].value; var geolong = resultsElem.getElementsByClassName('geolong')[0].value; var point = new GLatLng(geolat, geolong); waypoints[i] = point; } if(waypoints.length == 1){ map.setCenter(waypoints[0], 16); map.addOverlay(new GMarker(waypoints[0])); resultsElem.getElementsByClassName('numHolder')[0].innerHTML = ''; }else{ map.setCenter(waypoints[0], 16); for(j=0; j< waypoints.length; j++) { var vLoc = waypoints[j]; var vInfo = resultsElem.getElementByClassName('resultBox[j]]').innerHTML; //unfinished function to mine name out of div and make it the marker title //x = resultsElem.getElementsByTagName("b"); // for (i=0;i<x.length;i++) // //marker.value = resultsElem.getElementBy('numHolder').innerHTML var marker = createMarker(vLoc, vInfo); map.addOverlay(marker); } } function createMarker(vLoc, vInfo) { var marker = (new GMarker(vLoc)); var cont = vInfo; GEvent.addListener(marker, 'click', function() { marker.openInfoWindowHtml(cont); }); return marker; } //var directions = new GDirections(window.map, document.getElementById('directionsPanel')); //directions.loadFromWaypoints(waypoints, { travelMode: G_TRAVEL_MODE_WALKING }); //GEvent.addListener(directions, "load" , function() { // var numRoutes = directions.getNumRoutes(); // for(j=0; j< numRoutes; j++){ // var thisRoute = directions.getRoute(j); // var routeText = ''; // for(k=0; k < thisRoute.getNumSteps(); k++){ // var thisStep = thisRoute.getStep(k); // if(k != 0){ routeText += "  ||  "; } // routeText += thisStep.getDescriptionHtml(); // } // $('resultDirections' + j).innerHTML = routeText; // } // $('resultDirections' + numRoutes).hide(); //}); } function moveUp(_obj){ var parentObj = $(_obj).up().up(); var prevSib = parentObj.previous(); prevSib.insert({before: parentObj}); processResults(); } function moveDown(_obj){ var parentObj = $(_obj).up().up(); var nextSib = parentObj.next(); nextSib.insert({after: parentObj}); processResults(); }

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PHP: How to automate building a 100 <UL>/<LI> menuitems, while keeping the Menu Structure File Flat / Simply Managable?

- by Sam

Above: current "stupid" menu. (entire ul/li menu for javascript menu system) + (some li lines as page-specific submenu) Hi folks! With passion for automation and elegancy, but limited knowledge/knowhow, im stuck with "my hands in my hair" as we Dutch say, for my current menu system works perfectly, but is a pain in the a*s to update! So, i would appreciate it greatly, if you can suggest how to automate this in php: how to let the php generate the html menu code basing on a flat menu input file with TABS indented. OLD SITUATION <ul>  <li><a href="carrot.php"><p class="mnu" style="background-position:0 -820px"><? echo __("carrot juice") ?></p></a></li>  </ul a javascript file reads a ul/li structure as input to build menu of format in that ul/li, the items with a hyperlink and sprite-bg position represent webpages, (inside LI) while items without hyperlink and sprite-bg are just headers of that menusection, (inside H6) to highlight the current page in the menu, the javascript menumaker uses an id number. this number corresponds to the consequtive li that is a webpage, skips h6 headers correctly. these h6 headers are only there for when importing sections of the same menu as submenu. non-li headers are not shown in menu, nore counted by the javascript menu for their ID. to know which page should be shown, i have to count from ID 0, the li items till finding the current webpage in the li structure and then manually put it in each webpage! BUT: changing an item in li order, means stupidly re-counting their entire li again! each webpage has an icon (= sprite bg-position numer), which is also used in the webpage. INTENDED RESULT I dream of, once setting what the current webpage is (e.g carrot.php) the menu system automatically "finds" and "counts" the li's and returns the id nr (for proper highlight of main menu); generates the entire menu html, and depending on which headings are set for submenu, (e.g. meals, drinks) generates those submenu (entire section below each given header); ginally adds h5 highlight inside the li of that submenu item. For the menu, i wish an easily readable, simple plain txt menu that is indented with tabs, (each tab is one depth for example) and further tabs follow for url and sprite position of icon. MY DREAM MENU-MANAGEMENT FILE |>TAB SEPARATED/INDENTED FLATMENU FILE |MUST BE CALCULATED BY PHP: |>MENUTEXT============URL=============SPRITE=====|ID===TAG================== |>about "#" -520 |00 li |> INFORMATION |—— h6 |> physical state "physical.php" -920 |01 li |> mental health "mental.php" -10 |02 li |> |>apetite "#" -1290 |03 li |> meals "#" -600 |04 li |> COLD MEAL |—— h6 |> egg salade "salad.php" -1040 |05 li |> salmon fish "salmon.php" -540 |06 li |> HOT MEAL |—— h6 |> spare ribs "spareribs.php" -120 |07 li |> di macaroni "macaroni.php" -870 |08 li |> |> drinks "#" -230 |09 li |> JUCY DRINK |—— h6 |> carrot juice "carrot.php" -820 |10 li |> mango hive "mango.php" -270 |11 li DESIRED CHRONOLOGY php outputs the entire ul/li html so the javascript can show the menu: webpage items go inside li tags, and header items go inside h6 tags, e.g. <h6>JUCY DRINK</h6> Each website page has a url filename [eg: salad.php]. Based on this given fact, the php menu generator detects the pagename, gives the IDnr of the position of that page according to the li-item nr and sets variable for javascript to highlight current menu item. the menu items below the specified headers are loaded as submenu in which the current page.php is wrapped inside h5 to highlight current page in submenu: e.g. (<li><h5><a href="carrot.php"><p>..etc..</p></h5></li> Question Which methods / steps / (chronological)ways are there for doing this? I am no good in php programming, but am learning it so please dont write any code without a line of comment why I should use that method etc. Where do I start? If I am unclear in my question, please ask. Thanks. Much appreciated!! Concrete Task List from the provided Comments/Answers, sofar: (RobertB) First, get some PHP code working that can read through a tab-delimited file and put the data into an appropriate data structure. NOW WORKING AT THIS

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c++ / c confusion

- by mrbuxley

Im trying to make a small app in c++ that saves midifiles with this library. http://musicnote.sourceforge.net/docs/html/index.html The sample code that is given on the homepage looks like this. #include "MusicNoteLib.h" void main() { MusicNoteLib::Player player; // Create the Player Object player.Play("C D E F G A B"); // Play the Music Notes on the default MIDI output port } This piece of code won't compile in Visual studio 2008, I get many errors like MusicNoteLib.h(22) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int I don't understand the error or where to start looking... There also was some dll files that can be used instead of this h file. #ifndef __MUSICNOTE_LIB_H__EBEE094C_FF6E_43a1_A6CE_D619564F9C6A__ #define __MUSICNOTE_LIB_H__EBEE094C_FF6E_43a1_A6CE_D619564F9C6A__ /** @file MusicNoteLib.h * \brief Main header file for accessing the MusicNote Library */ /// <Summary> /// This header file can be included directly in your project or through /// MusicNoteLib.h of the MusicNoteDll project. If included directly, this /// will be built directly as a satic library. If included through MusicNoteDll /// this will use dllImports through MUSICNOTELIB_API /// </Summary> #ifndef MUSICNOTELIB_API #define MUSICNOTELIB_API #endif // MUSICNOTELIB_API //#include "Player.h" namespace MusicNoteLib /// Music Programming Library { typedef void (__stdcall *LPFNTRACEPROC)(void* pUserData, const TCHAR* szTraceMsg); typedef void (__stdcall *LPFNERRORPROC)(void* pUserData, long lErrCode, const TCHAR* szErrorMsg, const TCHAR* szToken); extern "C" { MUSICNOTELIB_API typedef void MStringPlayer; MUSICNOTELIB_API void* GetCarnaticMusicNoteReader(); /// <Summary> /// Creates a MusicString Player object. /// </Summary> MUSICNOTELIB_API MStringPlayer* CreateMusicStringPlayer(); /// <Summary> /// Plays Music string notes on the default MIDI Output device with the default Timer Resolution. /// Use PlayMusicStringWithOpts() to use custom values. /// @param szMusicNotes the Music string to be played on the MIDI output device /// @return True if the notes were played successfully, False otherwise /// </Summary> MUSICNOTELIB_API bool PlayMusicString(const TCHAR* szMusicNotes); /// <Summary> /// Same as PlayMusicString() except that this method accepts Callbacks. /// The Trace and Error callbacks will be used during the Parse of the Music Notes. /// @param szMusicNotes the Music string to be played on the MIDI output device /// @param traceCallbackProc the Callback to used to report Trace messages /// @param errorCallbackProc the Callback to used to report Error messages /// @param pUserData any user supplied data that should be sent to the Callback /// @return True if the notes were played successfully, False otherwise /// </Summary> MUSICNOTELIB_API bool PlayMusicStringCB(const TCHAR* szMusicNotes, LPFNTRACEPROC traceCallbackProc, LPFNERRORPROC errorCallbackProc, void* pUserData); /// <Summary> /// Plays Music string notes on the given MIDI Output device using the given Timer Resolution. /// Use PlayMusicString() to use default values. /// @param szMusicNotes the Music notes to be played /// @param nMidiOutPortID the device ID of the MIDI output port to be used for the play /// @param nTimerResMS preferred MIDI timer resolution, in MilliSeconds /// @return True if Play was successful, False otherwise /// </Summary> MUSICNOTELIB_API bool PlayMusicStringWithOpts(const TCHAR* szMusicNotes, int nMidiOutPortID, unsigned int nTimerResMS); /// <Summary> /// Same as PlayMusicStringWithOpts() except that this method accepts Callbacks. /// The Trace and Error callbacks will be used during the Parse of the Music Notes. /// @param szMusicNotes the Music notes to be played /// @param nMidiOutPortID the device ID of the MIDI output port to be used for the play /// @param nTimerResMS preferred MIDI timer resolution, in MilliSeconds /// @param traceCallbackProc the Callback to used to report Trace messages /// @param errorCallbackProc the Callback to used to report Error messages /// @param pUserData any user supplied data that should be sent to the Callback /// @return True if Play was successful, False otherwise /// </Summary> MUSICNOTELIB_API bool PlayMusicStringWithOptsCB(const TCHAR* szMusicNotes, int nMidiOutPortID, unsigned int nTimerResMS, LPFNTRACEPROC traceCallbackProc, LPFNERRORPROC errorCallbackProc, void* pUserData); /// <Summary> /// Save the given MusicString content into a MIDI output file /// @param szMusicNotes Music Notes to be converted to MIDI output /// @param szOutputFilePath path of the MIDI output file /// @return True if the the content was saved successfully, False otherwise /// </Summary> MUSICNOTELIB_API bool SaveAsMidiFile(const TCHAR* szMusicNotes, const char* szOutputFilePath); //MUSICNOTELIB_API typedef void (*ParseErrorProc)(const MusicNoteLib::CParser*, MusicNoteLib::CParser::ErrorEventHandlerArgs* pEvArgs); //MUSICNOTELIB_API typedef void (*ParseTraceProc)(const MusicNoteLib::CParser*, MusicNoteLib::CParser::TraceEventHandlerArgs* pEvArgs); MUSICNOTELIB_API void Parse(const TCHAR* szNotes, LPFNTRACEPROC traceCallbackProc, void* pUserData); } // extern "C" } // namespace MusicNoteLib #endif // __MUSICNOTE_LIB_H__EBEE094C_FF6E_43a1_A6CE_D619564F9C6A__

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how to click on a button in python

- by Ciobanu Alexandru

Trying to build some bot for clicking "skip-ad" button on a page. So far, i manage to use Mechanize to load a web-driver browser and to connect to some page but Mechanize module do not support js directly so now i need something like Selenium if i understand correct. I am also a beginner in programming so please be specific. How can i use Selenium or if there is any other solution, please explain details. This is the inner html code for the button: <a id="skip-ad" class="btn btn-inverse" onclick="open_url('http://imgur.com/gallery/tDK9V68', 'go'); return false;" style="font-weight: bold; " target="_blank" href="http://imgur.com/gallery/tDK9V68"> … </a> And this is my source so far: #!/usr/bin/python # FILENAME: test.py import mechanize import os, time from random import choice, randrange prox_list = [] #list of common UAS to apply to each connection attempt to impersonate browsers user_agent_strings = [ 'Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1468.0 Safari/537.36', 'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.1) Gecko/2008071615 Fedora/3.0.1-1.fc9 Firefox/3.0.1', 'Opera/9.80 (Windows NT 6.0) Presto/2.12.388 Version/12.14', 'Opera/9.80 (Macintosh; Intel Mac OS X 10.6.8; U; fr) Presto/2.9.168 Version/11.52', 'Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:23.0) Gecko/20131011 Firefox/23.0', 'Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; Media Center PC 6.0; InfoPath.3; MS-RTC LM 8; Zune 4.7', 'Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0; .NET CLR 2.0.50727; SLCC2; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; Zune 4.0; Tablet PC 2.0; InfoPath.3; .NET4.0C; .NET4.0E)', 'Mozilla/5.0 (compatible; MSIE 10.6; Windows NT 6.1; Trident/5.0; InfoPath.2; SLCC1; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET CLR 2.0.50727) 3gpp-gba UNTRUSTED/1.0', 'Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.0; Trident/5.0; chromeframe/11.0.696.57)', 'Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; InfoPath.1; SV1; .NET CLR 3.8.36217; WOW64; en-US)', 'Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; GTB7.4; InfoPath.2; SV1; .NET CLR 3.3.69573; WOW64; en-US)' ] def load_proxy_list(target): #loads and parses the proxy list file = open(target, 'r') count = 0 for line in file: prox_list.append(line) count += 1 print "Loaded " + str(count) + " proxies!" load_proxy_list('proxies.txt') #for i in range(1,(len(prox_list) - 1)): # depreceated for overloading for i in range(1,30): br = mechanize.Browser() #pick a random UAS to add some extra cover to the bot br.addheaders = [('User-agent', choice(user_agent_strings))] print "----------------------------------------------------" #This is bad internet ethics br.set_handle_robots(False) #choose a proxy proxy = choice(prox_list) br.set_proxies({"http": proxy}) br.set_debug_http(True) try: print "Trying connection with: " + str(proxy) #currently using: BTC CoinURL - Grooveshark Broadcast br.open("http://cur.lv/4czwj") print "Opened successfully!" #act like a nice little drone and view the ads sleep_time_on_link = randrange(17.0,34.0) time.sleep(sleep_time_on_link) except mechanize.HTTPError, e: print "Oops Request threw " + str(e.code) #future versions will handle codes properly, 404 most likely means # the ad-linker has noticed bot-traffic and removed the link # or the used proxy is terrible. We will either geo-locate # proxies beforehand and pick good hosts, or ditch the link # which is worse case scenario, account is closed because of botting except mechanize.URLError, e: print "Oops! Request was refused, blacklisting proxy!" + str(e) prox_list.remove(proxy) del br #close browser entirely #wait between 5-30 seconds like a good little human sleep_time = randrange(5.0, 30.0) print "Waiting for %.1f seconds like a good bot." % (sleep_time) time.sleep(sleep_time)

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Runtime error on UVa Online Judge on Erdos Number

- by 2012 - End of the World

I am solving the Erdos number problem from the programming challenges in JAVA. The code runs perfectly in my machine. However on the online judge it results in a runtime error. Could anyone point out the mistake i made? http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=985 Here is the code import java.util.*; import java.io.*; class Main { private String inputLines[]; private String namesToBeFound[]; private String namesInEachBook[][]; private String searchItem; private boolean solnfound=false; private static final BufferedReader br =new BufferedReader(new InputStreamReader(System.in)); static String read() throws IOException { String line; while(true) { line=br.readLine(); if(line==null) break; //eof else if(line.length()==0) continue; //blank line else { line=line.trim().replaceAll("\\s+"," "); return line; } } return null; } public static void main(String args[]) throws IOException { Main ob=new Main(); int totalPapers,calcAuthors,totalScenarios; //First input number of scenarios totalScenarios=Integer.parseInt(read()); //Now start a loop for reading total number of scenarios for(int scenario=1;scenario<=totalScenarios;scenario++) { //Now read the line containing the number of papers and authors StringTokenizer line=new StringTokenizer(read()," "); totalPapers=Integer.parseInt(line.nextToken()); calcAuthors=Integer.parseInt(line.nextToken()); //Read a line containing author names along with book names ob.inputLines=new String[totalPapers]; for(int i=0;i<totalPapers;i++) ob.inputLines[i]=read(); //Read a line containing the names to be searched ob.namesToBeFound=new String[calcAuthors]; for(int i=0;i<calcAuthors;i++) ob.namesToBeFound[i]=read(); //Now generate the array ob.buildArray(); //Now search System.out.println("Scenario "+scenario); for(int i=0;i<calcAuthors;i++) { ob.searchItem=ob.namesToBeFound[i]; if(ob.searchItem.equals("Erdos, P.")) { System.out.println("Erdos, P. 0"); continue; } ob.search(ob.namesToBeFound[i],1,new ArrayList()); if(ob.solnfound==false) System.out.println(ob.searchItem+" infinity"); ob.solnfound=false; } } } private void buildArray() { String str; namesInEachBook=new String[inputLines.length][]; for(int i=0;i<inputLines.length;i++) { str=inputLines[i]; str=str.substring(0,str.indexOf(':')); str+=","; namesInEachBook[i]=new String[(countCommas(str)+1)>>1]; for(int j=0;j<namesInEachBook[i].length;j++) { str=str.trim(); namesInEachBook[i][j]=""; namesInEachBook[i][j]+=str.substring(0,str.indexOf(','))+","; str=str.substring(str.indexOf(',')+1); namesInEachBook[i][j]+=str.substring(0,str.indexOf(',')); str=str.substring(str.indexOf(',')+1); } } } private int countCommas(String s) { int num=0; for(int i=0;i<s.length();i++) if(s.charAt(i)==',') num++; return num; } private void search(String searchElem,int ernosDepth,ArrayList searchedElem) { ArrayList searchSpace=new ArrayList(); searchedElem.add(searchElem); for(int i=0;i<namesInEachBook.length;i++) for(int j=0;j<namesInEachBook[i].length;j++) { if(namesInEachBook[i][j].equals(searchElem)) //Add all authors name in this group { for(int k=0;k<namesInEachBook[i].length;k++) { if(namesInEachBook[i][k].equals("Erdos, P.")) //Found { solnfound=true; System.out.println(searchItem+" "+ernosDepth); return; } else if(searchedElem.contains(namesInEachBook[i][k]) || searchSpace.contains(namesInEachBook[i][k])) continue; searchSpace.add(namesInEachBook[i][k]); } break; } } Iterator i=searchSpace.iterator(); while(i.hasNext()) { String cSearchElem=(String)i.next(); search(cSearchElem,ernosDepth+1,searchedElem); } } }

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Login or Register (Ruby on rails)

- by DanielZ

Hello stackoverflow, I'm working on an Ruby on Rails application (2.3.x) and i want to make a form that lets the user login or register. I want to do this in the same form. I have a JS function that replaces the form elements like this: Login form: <% form_for @user do |f| %> <div id="form"> <%= f.label :email, "E-mail" %> <%= f.text_field :email %> <%= f.label :password, "Password" %> <%= f.password_field :password %> <%= link_to "I don't have an account, "#", :id => "changeForm"%> <%= f.submit "Login" %> </div> <% end %> The id "changeForm" triggers a JS function that changes the form elements. So if you press the url the html looks like this: <% form_for @user do |f| %> <div id="form"> <%= f.label :name, "Name" %> <%= f.text_field :name %> <%= f.label :email, "E-mail" %> <%= f.text_field :email %> <%= f.label :password, "Password" %> <%= f.password_field :password %> <%= f.label :password_confirmation, "Password confirmation" %> <%= f.password_field :password_confirmation %> <%= link_to "I do have an account, "#", :id => "changeForm"%> <%= f.submit "Register" %> </div> <% end %> I added the neccesary validations to my user model: class User < ActiveRecord::Base attr_reader :password validates_presence_of :name, :email, :password validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i validates_confirmation_of :password But what happens when you fill in the email / password you get the errors that the name is missing and that the password fields aren't confirmed. So i could do some nasty programming in my user model like this: #if password_conf or the name are present the user has tried to register... if params[:user][:password_confirmation].present? || params[:user][:name].present? #so we'll try to save the user if @user.save #if the user is saved authenticate the user current_session.user = User.authenticate(params[:user]) #if the user is logged in? if current_session.user.present? flash[:notice] = "succesvully logged redirect_to some_routes_path else #not logged in... flash[:notice] = "Not logged in" render :action => "new" end else #user not saved render :action => "new" end else #So if the params[:user][:password_confirmation] or [:user][:name] weren't present we geuss the user wants to login... current_session.user = User.authenticate(params[:user]) #are we logged_in? if current_session.user.present? flash[:notice] = "Succesvully logged in" redirect_to some_routes_path else #errors toevoegen @user.errors.add(:email, "The combination of email/password isn't valid") @user.errors.add(:password," ") render :action => "new" end end end Without validations this (imho dirty code and should not be in the controller) works. But i want to use the validates_presence_of methods and i don't want to slap the "conventions over configurations" in the face. So another thing i have tried is adding a hidden field to the form: #login form <%= f.hidden_field :login, :value => true %> # and ofcourse set it to false if we want to register. And then i wanted to use the method: before_validation before_validation_on_create do |user| if params[:user].login == true #throws an error i know... validates_presence_of :email, :password validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i else validates_presence_of :name, :email, :password validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i validates_confirmation_of :password end end But this doesn't work because i can't access the params. And login isn't a attribute for the user object. But i thought that in this way i could validate the email and password params if the user wants to login. And all the other attrs if the user want to register. So all i could think of doesn't work how i want it to work. So my main goal is this: 1 form for login/register with the use of the validation methods in the user model. So if we want to login but don't fill in any information = give validation errors. And if the user wants to login but the email/password combination doens't match give the "@user.errors.add(:email, "the combination wasn't found in the db...")". And the same goes for user register... Thanks in advance!

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Mistake in display and insert methods (double-ended queue)

- by MANAL

1) My problem when i make remove from right or left program will be remove true but when i call diplay method the content wrong like this I insert 12 43 65 23 and when make remove from left program will remove 12 but when call display method show like this 12 43 65 and when make remove from right program will remove 23 but when call display method show like this 12 43 Why ?????? ); and when i try to make insert after remove write this Can not insert right because the queue is full . first remove right and then u can insert right where is the problem ?? Please Help me please 2) My code FIRST CLASS class dqueue { private int fullsize; //number of all cells private int item_num; // number of busy cells only private int front,rear; public int j; private double [] dqarr; //========================================== public dqueue(int s) //constructor { fullsize = s; front = 0; rear = -1; item_num = 0; dqarr = new double[fullsize]; } //========================================== public void insert(double data) { if (rear == fullsize-1) rear = -1; rear++; dqarr[rear] = data; item_num++; } public double removeLeft() // take item from front of queue { double temp = dqarr[front++]; // get value and incr front if(front == fullsize) front = 0; item_num --; // one less item return temp; } public double removeRight() // take item from rear of queue { double temp = dqarr[rear--]; // get value and decr rear if(rear == -1) // rear = item_num -1; item_num --; // one less item return temp; } //========================================= public void display () //display items { for (int j=0;j<item_num;j++) // for every element System.out.print(dqarr[j] +" " ); // display it System.out.println(""); } //========================================= public int size() //number of items in queue { return item_num; } //========================================== public boolean isEmpty() // true if queue is empty { return (item_num ==0); } } SECOND CLASS import java.util.Scanner; class dqueuetest { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println(" ***** Welcome here***** "); System.out.println(" ***** Mind Of Programming Group***** "); System.out.println(" _____________________________________________ "); System.out.println("enter size of your dqueue"); int size = input.nextInt(); dqueue mydq = new dqueue(size); System.out.println(""); System.out.println("enter your itemes"); //===================================== for(int i = 0;i<=size-1;i++) { System.out.printf("item %d:",i+1); double item = input.nextDouble(); mydq.insert(item); System.out.println(""); } //===================================== int queue =size ; int c = 0 ; while (c != 6) { System.out.println(""); System.out.println("************************************************"); System.out.println(" MAIN MENUE"); System.out.println("1- INSERT RIGHT "); System.out.println("2- REMOVE LEFT"); System.out.println("3- REMOVE RIGHT"); System.out.println("4- DISPLAY"); System.out.println("5- SIZE"); System.out.println("6- EXIT"); System.out.println("************************************************"); System.out.println("choose your operation by number(1-6)"); c = input.nextInt(); switch (c) { case 1: if (queue == size) System.out.print("Can not insert right because the queue is full . first remove right and then u can insert right "); else { System.out.print("enter your item: "); double item = input.nextDouble(); mydq.insert(item);} break; case 2: System.out.println("REMOVE FROM REAR :"); if( !mydq.isEmpty() ) { double item = mydq.removeLeft(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 3: System.out.println("REMOVE FROM FRONT :"); if( !mydq.isEmpty() ) { double item = mydq.removeRight(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 4: System.out.println("The items in Queue are :"); mydq.display(); break; case 5: System.out.println("The Size of the Queue is :"+mydq.size()); break; case 6: System.out.println("Good Bye"); break; default: System.out.println("wrong chiose enter again"); } //end switch } //end while } // end main }//end class

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Does this language feature already exist?

- by Pindatjuh

I'm currently developing a new language for programming in a continuous environment (compare it to electrical engineering), and I've got some ideas on a certain language construction. Let me explain the feature by explanation and then by definition: x = a U b; Where x is a variable and a and b are other variables (or static values). This works like a union between a and b; no duplicates and no specific order. with(x) { // regular 'with' usage; using the global interpretation of "x" x = 5; // will replace the original definition of "x = a U b;" } with(x = a) { // this code block is executed when the "x" variable // has the "a" variable assigned. All references in // this code-block to "x" are references to "a". So saying: x = 5; // would only change the variable "a". If the variable "a" // later on changes, x still equals to 5, in this fashion: // 'x = a U b U 5;' // '[currentscope] = 5;' // thus, 'a = 5;' } with(x = b) { // same but with "b" } with(x != a) { // here the "x" variable refers to any variable // but "a"; thus saying x = 5; // is equal to the rewriting of // 'x = a U b U 5;' // 'b = 5;' (since it was the scope of this block) } with(x = (a U b)) { // guaranteed that "x" is 'a U b'; interacting with "x" // will interact with both "a" and "b". x = 5; // makes both "a" and "b" equal to 5; also the "x" variable // is updated to contain: // 'x = a U b U 5;' // '[currentscope] = 5;' // 'a U b = 5;' // and thus: 'a = 5; b = 5;'. } // etc. In the above, all code-blocks are executed, but the "scope" changes in each block how x is interpreted. In the first block, x is guaranteed to be a: thus interacting with x inside that block will interact on a. The second and the third code-block are only equal in this situation (because not a: then there only remains b). The last block guarantees that x is at least a or b. Further more; U is not the "bitwise or operator", but I've called it the "and/or"-operator. Its definition is: "U" = "and" U "or" (On my blog, http://cplang.wordpress.com/2009/12/19/binop-and-or/, there is more (mathematical) background information on this operator. It's loosely based on sets. Using different syntax, changed it in this question.) Update: more examples. print = "Hello world!" U "How are you?"; // this will print // both values, but the // order doesn't matter. // 'userkey' is a variable containing a key. with(userkey = "a") { print = userkey; // will only print "a". } with(userkey = ("shift" U "a")) { // pressed both "shift" and the "a" key. print = userkey; // will "print" shift and "a", even // if the user also pressed "ctrl": // the interpretation of "userkey" is changed, // such that it only contains the matched cases. } with((userkey = "shift") U (userkey = "a")) { // same as if-statement above this one, showing the distributivity. } x = 5 U 6 U 7; y = x + x; // will be: // y = (5 U 6 U 7) + (5 U 6 U 7) // = 10 U 11 U 12 U 13 U 14 somewantedkey = "ctrl" U "alt" U "space" with(userkey = somewantedkey) { // must match all elements of "somewantedkey" // (distributed the Boolean equals operated) // thus only executed when all the defined keys are pressed } with(somewantedkey = userkey) { // matches only one of the provided "somewantedkey" // thus when only "space" is pressed, this block is executed. } Update2: more examples and some more context. with(x = (a U b)) { // this } // can be written as with((x = a) U (x = b)) { // this: changing the variable like x = 5; // will be rewritten as: // a = 5 and b = 5 } Some background information: I'm building a language which is "time-independent", like Java is "platform-independant". Everything stated in the language is "as is", and is continuously actively executed. This means; the programmer does not know in which order (unless explicitly stated using constructions) elements are, nor when statements are executed. The language is completely separated from the "time"-concept, i.e. it's continuously executed: with(a < 5) { a++; } // this is a loop-structure; // how and when it's executed isn't known however. with(a) { // everytime the "a" variable changes, this code-block is executed. b = 4; with(b < 3) { // runs only three times. } with(b > 0) { b = b - 1; // runs four times } } Update 3: After pondering on the type of this language feature; it closely resemblances Netbeans Platform's Lookup, where each "with"-statement a synchronized agent is, working on it's specific "filter" of objects. Instead of type-based, this is variable-based (fundamentally quite the same; just a different way of identifiying objects). I greatly thank all of you for providing me with very insightful information and links/hints to great topics I can research. Thanks. I do not know if this construction already exists, so that's my question: does this language feature already exist?

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Sockets: Transport endpoint is not connected on send

- by TheoretiCAL

I'm trying to learn socket programming from http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html and am attempting to build a SOCK_STREAM client/server. My client: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #define SERVERPORT "4951" // the port users will be connecting to int main(int argc, char *argv[]) { int sockfd; struct addrinfo hints, *servinfo, *p; int rv; int numbytes; if (argc != 3) { fprintf(stderr,"usage: talker hostname message\n"); exit(1); } memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; hints.ai_socktype = SOCK_STREAM; if ((rv = getaddrinfo(argv[1], SERVERPORT, &hints, &servinfo)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); return 1; } // loop through all the results and make a socket for(p = servinfo; p != NULL; p = p->ai_next) { if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) { perror("talker: socket"); continue; if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) { close(sockfd); perror("client: connect"); continue; } } break; } if (p == NULL) { fprintf(stderr, "talker: failed to bind socket\n"); return 2; } if ((numbytes = send(sockfd, argv[2], strlen(argv[2]), 0) == -1)) { perror("talker: send"); exit(1); } freeaddrinfo(servinfo); printf("talker: sent %d bytes to %s\n", numbytes, argv[1]); close(sockfd); return 0; } Server: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #define MYPORT "4951" // the port users will be connecting to #define MAXBUFLEN 100 static int backlog = 10; // get sockaddr, IPv4 or IPv6: void *get_in_addr(struct sockaddr *sa) { if (sa->sa_family == AF_INET) { return &(((struct sockaddr_in*)sa)->sin_addr); } return &(((struct sockaddr_in6*)sa)->sin6_addr); } int main(void) { int sockfd; struct addrinfo hints, *servinfo, *p; int rv; int numbytes; int new_fd; socklen_t addr_size; struct sockaddr_storage their_addr; char buf[MAXBUFLEN]; char s[INET6_ADDRSTRLEN]; memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; // set to AF_INET to force IPv4 hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // use my IP if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); return 1; } // loop through all the results and bind to the first we can for(p = servinfo; p != NULL; p = p->ai_next) { if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) { perror("listener: socket"); continue; } int yes=1; // lose the pesky "Address already in use" error message if (setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) { perror("setsockopt"); exit(1); } if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) { close(sockfd); perror("listener: bind"); continue; } if (listen(sockfd,backlog) == -1){ close(sockfd); perror("listener:listen"); continue; } break; } if (p == NULL) { fprintf(stderr, "listener: failed to bind socket\n"); return 2; } freeaddrinfo(servinfo); printf("listener: waiting to recv..\n"); while(1){ addr_size = sizeof their_addr; if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &addr_size))==-1){ perror("accept"); exit(1); } if ((numbytes = recv(new_fd, buf, MAXBUFLEN-1 , 0) == -1)) { perror("recv"); exit(1); } printf("listener: got packet from %s\n", inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), s, sizeof s)); printf("listener: packet is %d bytes long\n", numbytes); buf[numbytes] = '\0'; printf("listener: packet contains \"%s\"\n", buf); close(sockfd); } return 0; } Upon executing the client, I get " send: Transport endpoint is not connected" and I'm not sure where I went wrong. Thanks.

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C++ Program performs better when piped

- by ET1 Nerd

I haven't done any programming in a decade. I wanted to get back into it, so I made this little pointless program as practice. The easiest way to describe what it does is with output of my --help codeblock: ./prng_bench --help ./prng_bench: usage: ./prng_bench $N $B [$T] This program will generate an N digit base(B) random number until all N digits are the same. Once a repeating N digit base(B) number is found, the following statistics are displayed: -Decimal value of all N digits. -Time & number of tries taken to randomly find. Optionally, this process is repeated T times. When running multiple repititions, averages for all N digit base(B) numbers are displayed at the end, as well as total time and total tries. My "problem" is that when the problem is "easy", say a 3 digit base 10 number, and I have it do a large number of passes the "total time" is less when piped to grep. ie: command ; command |grep took : ./prng_bench 3 10 999999 ; ./prng_bench 3 10 999999|grep took .... Pass# 999999: All 3 base(10) digits = 3 base(10). Time: 0.00005 secs. Tries: 23 It took 191.86701 secs & 99947208 tries to find 999999 repeating 3 digit base(10) numbers. An average of 0.00019 secs & 99 tries was needed to find each one. It took 159.32355 secs & 99947208 tries to find 999999 repeating 3 digit base(10) numbers. If I run the same command many times w/o grep time is always VERY close. I'm using srand(1234) for now, to test. The code between my calls to clock_gettime() for start and stop do not involve any stream manipulation, which would obviously affect time. I realize this is an exercise in futility, but I'd like to know why it behaves this way. Below is heart of the program. Here's a link to the full source on DB if anybody wants to compile and test. https://www.dropbox.com/s/6olqnnjf3unkm2m/prng_bench.cpp clock_gettime() requires -lrt. for (int pass_num=1; pass_num<=passes; pass_num++) { //Executes $passes # of times. clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &temp_time); //get time start_time = timetodouble(temp_time); //convert time to double, store as start_time for(i=1, tries=0; i!=0; tries++) { //loops until 'comparison for' fully completes. counts reps as 'tries'. <------------ for (i=0; i<Ndigits; i++) //Move forward through array. | results[i]=(rand()%base); //assign random num of base to element (digit). | /*for (i=0; i<Ndigits; i++) //---Debug Lines--------------- | std::cout<<" "<<results[i]; //---a LOT of output.---------- | std::cout << "\n"; //---Comment/decoment to disable/enable.*/ // | for (i=Ndigits-1; i>0 && results[i]==results[0]; i--); //Move through array, != element breaks & i!=0, new digits drawn. -| } //If all are equal i will be 0, nested for condition satisfied. -| clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &temp_time); //get time draw_time = (timetodouble(temp_time) - start_time); //convert time to dbl, subtract start_time, set draw_time to diff. total_time += draw_time; //add time for this pass to total. total_tries += tries; //add tries for this pass to total. /*Formated output for each pass: Pass# ---: All -- base(--) digits = -- base(10) Time: ----.---- secs. Tries: ----- (LINE) */ std::cout<<"Pass# "<<std::setw(width_pass)<<pass_num<<": All "<<Ndigits<<" base("<<base<<") digits = " <<std::setw(width_base)<<results[0]<<" base(10). Time: "<<std::setw(width_time)<<draw_time <<" secs. Tries: "<<tries<<"\n"; } if(passes==1) return 0; //No need for totals and averages of 1 pass. /* It took ----.---- secs & ------ tries to find --- repeating -- digit base(--) numbers. (LINE) An average of ---.---- secs & ---- tries was needed to find each one. (LINE)(LINE) */ std::cout<<"It took "<<total_time<<" secs & "<<total_tries<<" tries to find " <<passes<<" repeating "<<Ndigits<<" digit base("<<base<<") numbers.\n" <<"An average of "<<total_time/passes<<" secs & "<<total_tries/passes <<" tries was needed to find each one. \n\n"; return 0;

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How do I make my applet turn the user's input into an integer and compare it to the computer's random number?

- by Kitteran

I'm in beginning programming and I don't fully understand applets yet. However, (with some help from internet tutorials) I was able to create an applet that plays a game of guess with the user. The applet compiles fine, but when it runs, this error message appears: "Exception in thread "main" java.lang.NumberFormatException: For input string: "" at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48) at java.lang.Integer.parseInt(Integer.java:470) at java.lang.Integer.parseInt(Integer.java:499) at Guess.createUserInterface(Guess.java:101) at Guess.<init>(Guess.java:31) at Guess.main(Guess.java:129)" I've tried moving the "userguess = Integer.parseInt( t1.getText() );" on line 101 to multiple places, but I still get the same error. Can anyone tell me what I'm doing wrong? The Code: // Creates the game GUI. import javax.swing.*; import java.awt.*; import java.awt.event.*; public class Guess extends JFrame{ private JLabel userinputJLabel; private JLabel lowerboundsJLabel; private JLabel upperboundsJLabel; private JLabel computertalkJLabel; private JButton guessJButton; private JPanel guessJPanel; static int computernum; int userguess; static void declare() { computernum = (int) (100 * Math.random()) + 1; //random number picked (1-100) } // no-argument constructor public Guess() { createUserInterface(); } // create and position GUI components private void createUserInterface() { // get content pane and set its layout Container contentPane = getContentPane(); contentPane.setLayout( null ); contentPane.setBackground( Color.white ); // set up userinputJLabel userinputJLabel = new JLabel(); userinputJLabel.setText( "Enter Guess Here -->" ); userinputJLabel.setBounds( 0, 65, 120, 50 ); userinputJLabel.setHorizontalAlignment( JLabel.CENTER ); userinputJLabel.setBackground( Color.white ); userinputJLabel.setOpaque( true ); contentPane.add( userinputJLabel ); // set up lowerboundsJLabel lowerboundsJLabel = new JLabel(); lowerboundsJLabel.setText( "Lower Bounds Of Guess = 1" ); lowerboundsJLabel.setBounds( 0, 0, 170, 50 ); lowerboundsJLabel.setHorizontalAlignment( JLabel.CENTER ); lowerboundsJLabel.setBackground( Color.white ); lowerboundsJLabel.setOpaque( true ); contentPane.add( lowerboundsJLabel ); // set up upperboundsJLabel upperboundsJLabel = new JLabel(); upperboundsJLabel.setText( "Upper Bounds Of Guess = 100" ); upperboundsJLabel.setBounds( 250, 0, 170, 50 ); upperboundsJLabel.setHorizontalAlignment( JLabel.CENTER ); upperboundsJLabel.setBackground( Color.white ); upperboundsJLabel.setOpaque( true ); contentPane.add( upperboundsJLabel ); // set up computertalkJLabel computertalkJLabel = new JLabel(); computertalkJLabel.setText( "Computer Says:" ); computertalkJLabel.setBounds( 0, 130, 100, 50 ); //format (x, y, width, height) computertalkJLabel.setHorizontalAlignment( JLabel.CENTER ); computertalkJLabel.setBackground( Color.white ); computertalkJLabel.setOpaque( true ); contentPane.add( computertalkJLabel ); //Set up guess jbutton guessJButton = new JButton(); guessJButton.setText( "Enter" ); guessJButton.setBounds( 250, 78, 100, 30 ); contentPane.add( guessJButton ); guessJButton.addActionListener( new ActionListener() // anonymous inner class { // event handler called when Guess button is pressed public void actionPerformed( ActionEvent event ) { guessActionPerformed( event ); } } // end anonymous inner class ); // end call to addActionListener // set properties of application's window setTitle( "Guess Game" ); // set title bar text setSize( 500, 500 ); // set window size setVisible( true ); // display window //create text field TextField t1 = new TextField(); // Blank text field for user input t1.setBounds( 135, 78, 100, 30 ); contentPane.add( t1 ); userguess = Integer.parseInt( t1.getText() ); //create section for computertalk Label computertalkLabel = new Label(""); computertalkLabel.setBounds( 115, 130, 300, 50); contentPane.add( computertalkLabel ); } // Display computer reactions to user guess private void guessActionPerformed( ActionEvent event ) { if (userguess > computernum) //if statements (computer's reactions to user guess) computertalkJLabel.setText( "Computer Says: Too High" ); else if (userguess < computernum) computertalkJLabel.setText( "Computer Says: Too Low" ); else if (userguess == computernum) computertalkJLabel.setText( "Computer Says:You Win!" ); else computertalkJLabel.setText( "Computer Says: Error" ); } // end method oneJButtonActionPerformed // end method createUserInterface // main method public static void main( String args[] ) { Guess application = new Guess(); application.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE); } // end method main } // end class Phone

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Mistake in dispaly and insert method (double - ended queue)

- by MANAL

1) My problem when i make remove from right or left program will be remove true but when i call diplay method the content wrong like this I insert 12 43 65 23 and when make remove from left program will remove 12 but when call display method show like this 12 43 65 and when make remove from right program will remove 23 but when call display method show like this 12 43 Why ?????? ); and when i try to make insert after remove write this Can not insert right because the queue is full . first remove right and then u can insert right where is the problem ?? Please Help me please 2) My code FIRST CLASS class dqueue { private int fullsize; //number of all cells private int item_num; // number of busy cells only private int front,rear; public int j; private double [] dqarr; //========================================== public dqueue(int s) //constructor { fullsize = s; front = 0; rear = -1; item_num = 0; dqarr = new double[fullsize]; } //========================================== public void insert(double data) { if (rear == fullsize-1) rear = -1; rear++; dqarr[rear] = data; item_num++; } public double removeLeft() // take item from front of queue { double temp = dqarr[front++]; // get value and incr front if(front == fullsize) front = 0; item_num --; // one less item return temp; } public double removeRight() // take item from rear of queue { double temp = dqarr[rear--]; // get value and decr rear if(rear == -1) // rear = item_num -1; item_num --; // one less item return temp; } //========================================= public void display () //display items { for (int j=0;j //========================================= public int size() //number of items in queue { return item_num; } //========================================== public boolean isEmpty() // true if queue is empty { return (item_num ==0); } } SECOND CLASS import java.util.Scanner; class dqueuetest { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println(" Welcome here** "); System.out.println(" * Mind Of Programming Group*** "); System.out.println(" _________________________ "); System.out.println("enter size of your dqueue"); int size = input.nextInt(); dqueue mydq = new dqueue(size); System.out.println(""); System.out.println("enter your itemes"); //===================================== for(int i = 0;i<=size-1;i++) { System.out.printf("item %d:",i+1); double item = input.nextDouble(); mydq.insert(item); System.out.println(""); } //===================================== int queue =size ; int c = 0 ; while (c != 6) { System.out.println(""); System.out.println("**************************"); System.out.println(" MAIN MENUE"); System.out.println("1- INSERT RIGHT "); System.out.println("2- REMOVE LEFT"); System.out.println("3- REMOVE RIGHT"); System.out.println("4- DISPLAY"); System.out.println("5- SIZE"); System.out.println("6- EXIT"); System.out.println("**************************"); System.out.println("choose your operation by number(1-6)"); c = input.nextInt(); switch (c) { case 1: if (queue == size) System.out.print("Can not insert right because the queue is full . first remove right and then u can insert right "); else { System.out.print("enter your item: "); double item = input.nextDouble(); mydq.insert(item);} break; case 2: System.out.println("REMOVE FROM REAR :"); if( !mydq.isEmpty() ) { double item = mydq.removeLeft(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 3: System.out.println("REMOVE FROM FRONT :"); if( !mydq.isEmpty() ) { double item = mydq.removeRight(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 4: System.out.println("The items in Queue are :"); mydq.display(); break; case 5: System.out.println("The Size of the Queue is :"+mydq.size()); break; case 6: System.out.println("Good Bye"); break; default: System.out.println("wrong chiose enter again"); } //end switch } //end while } // end main }//end class

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Loop crashing program having to do with 2D arrays

- by user450062

I am creating an encoding program and when I instruct the program to create a 5X5 grid based on the alphabet while skipping over letters that match up to certain pre-defined variables(which are given values by user input during runtime). I have a loop that instructs the loop to keep running until the values that access the array are out of bounds, the loop seems to cause the problem. This code is standardized so there shouldn't be much trouble compiling it in another compiler. Also would it be better to seperate my program into functions? here is the code: #include<iostream> #include<fstream> #include<cstdlib> #include<string> #include<limits> using namespace std; int main(){ while (!cin.fail()) { char type[81]; char filename[20]; char key [5]; char f[2] = "q"; char g[2] = "q"; char h[2] = "q"; char i[2] = "q"; char j[2] = "q"; char k[2] = "q"; char l[2] = "q"; int a = 1; int b = 1; int c = 1; int d = 1; int e = 1; string cipherarraytemplate[5][5]= { {"a","b","c","d","e"}, {"f","g","h","i","j"}, {"k","l","m","n","o"}, {"p","r","s","t","u"}, {"v","w","x","y","z"} }; string cipherarray[5][5]= { {"a","b","c","d","e"}, {"f","g","h","i","j"}, {"k","l","m","n","o"}, {"p","r","s","t","u"}, {"v","w","x","y","z"} }; cout<<"Enter the name of a file you want to create.\n"; cin>>filename; ofstream outFile; outFile.open(filename); outFile<<fixed; outFile.precision(2); outFile.setf(ios_base::showpoint); cin.ignore(std::numeric_limits<int>::max(),'\n'); cout<<"enter your codeword(codeword can have no repeating letters)\n"; cin>>key; while (key[a] != '\0' ){ while(b < 6){ cipherarray[b][c] = key[a]; if ( f == "q" ) { cipherarray[b][c] = f; } if ( f != "q" && g == "q" ) { cipherarray[b][c] = g; } if ( g != "q" && h == "q" ) { cipherarray[b][c] = h; } if ( h != "q" && i == "q" ) { cipherarray[b][c] = i; } if ( i != "q" && j == "q" ) { cipherarray[b][c] = j; } if ( j != "q" && k == "q" ) { cipherarray[b][c] = k; } if ( k != "q" && l == "q" ) { cipherarray[b][c] = l; } a++; b++; } c++; b = 1; } while (c < 6 || b < 6){ if (cipherarraytemplate[d][e] == f || cipherarraytemplate[d][e] == g || cipherarraytemplate[d][e] == h || cipherarraytemplate[d][e] == i || cipherarraytemplate[d][e] == j || cipherarraytemplate[d][e] == k || cipherarraytemplate[d][e] == l){ d++; } else { cipherarray[b][c] = cipherarraytemplate[d][e]; d++; b++; } if (d == 6){ d = 1; e++; } if (b == 6){ c++; b = 1; } } cout<<"now enter some text."<<endl<<"To end this program press Crtl-Z\n"; while(!cin.fail()){ cin.getline(type,81); outFile<<type<<endl; } outFile.close(); } } I know there is going to be some mid-forties guy out there who is going to stumble on to this post, he's have been programming for 20-some years and he's going to look at my code and say: "what is this guy doing".

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VS 2010 SP1 and SQL CE

- by ScottGu

Last month we released the Beta of VS 2010 Service Pack 1 (SP1). You can learn more about the VS 2010 SP1 Beta from Jason Zander’s two blog posts about it, and from Scott Hanselman’s blog post that covers some of the new capabilities enabled with it. You can download and install the VS 2010 SP1 Beta here. Last week I blogged about the new Visual Studio support for IIS Express that we are adding with VS 2010 SP1. In today’s post I’m going to talk about the new VS 2010 SP1 tooling support for SQL CE, and walkthrough some of the cool scenarios it enables. SQL CE – What is it and why should you care? SQL CE is a free, embedded, database engine that enables easy database storage. No Database Installation Required SQL CE does not require you to run a setup or install a database server in order to use it. You can simply copy the SQL CE binaries into the \bin directory of your ASP.NET application, and then your web application can use it as a database engine. No setup or extra security permissions are required for it to run. You do not need to have an administrator account on the machine. Just copy your web application onto any server and it will work. This is true even of medium-trust applications running in a web hosting environment. SQL CE runs in-memory within your ASP.NET application and will start-up when you first access a SQL CE database, and will automatically shutdown when your application is unloaded. SQL CE databases are stored as files that live within the \App_Data folder of your ASP.NET Applications. Works with Existing Data APIs SQL CE 4 works with existing .NET-based data APIs, and supports a SQL Server compatible query syntax. This means you can use existing data APIs like ADO.NET, as well as use higher-level ORMs like Entity Framework and NHibernate with SQL CE. This enables you to use the same data programming skills and data APIs you know today. Supports Development, Testing and Production Scenarios SQL CE can be used for development scenarios, testing scenarios, and light production usage scenarios. With the SQL CE 4 release we’ve done the engineering work to ensure that SQL CE won’t crash or deadlock when used in a multi-threaded server scenario (like ASP.NET). This is a big change from previous releases of SQL CE – which were designed for client-only scenarios and which explicitly blocked running in web-server environments. Starting with SQL CE 4 you can use it in a web-server as well. There are no license restrictions with SQL CE. It is also totally free. Easy Migration to SQL Server SQL CE is an embedded database – which makes it ideal for development, testing, and light-usage scenarios. For high-volume sites and applications you’ll probably want to migrate your database to use SQL Server Express (which is free), SQL Server or SQL Azure. These servers enable much better scalability, more development features (including features like Stored Procedures – which aren’t supported with SQL CE), as well as more advanced data management capabilities. We’ll ship migration tools that enable you to optionally take SQL CE databases and easily upgrade them to use SQL Server Express, SQL Server, or SQL Azure. You will not need to change your code when upgrading a SQL CE database to SQL Server or SQL Azure. Our goal is to enable you to be able to simply change the database connection string in your web.config file and have your application just work. New Tooling Support for SQL CE in VS 2010 SP1 VS 2010 SP1 includes much improved tooling support for SQL CE, and adds support for using SQL CE within ASP.NET projects for the first time. With VS 2010 SP1 you can now: Create new SQL CE Databases Edit and Modify SQL CE Database Schema and Indexes Populate SQL CE Databases within Data Use the Entity Framework (EF) designer to create model layers against SQL CE databases Use EF Code First to define model layers in code, then create a SQL CE database from them, and optionally edit the DB with VS Deploy SQL CE databases to remote servers using Web Deploy and optionally convert them to full SQL Server databases You can take advantage of all of the above features from within both ASP.NET Web Forms and ASP.NET MVC based projects. Download You can enable SQL CE tooling support within VS 2010 by first installing VS 2010 SP1 (beta). Once SP1 is installed, you’ll also then need to install the SQL CE Tools for Visual Studio download. This is a separate download that enables the SQL CE tooling support for VS 2010 SP1. Walkthrough of Two Scenarios In this blog post I’m going to walkthrough how you can take advantage of SQL CE and VS 2010 SP1 using both an ASP.NET Web Forms and an ASP.NET MVC based application. Specifically, we’ll walkthrough: How to create a SQL CE database using VS 2010 SP1, then use the EF4 visual designers in Visual Studio to construct a model layer from it, and then display and edit the data using an ASP.NET GridView control. How to use an EF Code First approach to define a model layer using POCO classes and then have EF Code-First “auto-create” a SQL CE database for us based on our model classes. We’ll then look at how we can use the new VS 2010 SP1 support for SQL CE to inspect the database that was created, populate it with data, and later make schema changes to it. We’ll do all this within the context of an ASP.NET MVC based application. You can follow the two walkthroughs below on your own machine by installing VS 2010 SP1 (beta) and then installing the SQL CE Tools for Visual Studio download (which is a separate download that enables SQL CE tooling support for VS 2010 SP1). Walkthrough 1: Create a SQL CE Database, Create EF Model Classes, Edit the Data with a GridView This first walkthrough will demonstrate how to create and define a SQL CE database within an ASP.NET Web Form application. We’ll then build an EF model layer for it and use that model layer to enable data editing scenarios with an <asp:GridView> control. Step 1: Create a new ASP.NET Web Forms Project We’ll begin by using the File->New Project menu command within Visual Studio to create a new ASP.NET Web Forms project. We’ll use the “ASP.NET Web Application” project template option so that it has a default UI skin implemented: Step 2: Create a SQL CE Database Right click on the “App_Data” folder within the created project and choose the “Add->New Item” menu command: This will bring up the “Add Item” dialog box. Select the “SQL Server Compact 4.0 Local Database” item (new in VS 2010 SP1) and name the database file to create “Store.sdf”: Note that SQL CE database files have a .sdf filename extension. Place them within the /App_Data folder of your ASP.NET application to enable easy deployment. When we clicked the “Add” button above a Store.sdf file was added to our project: Step 3: Adding a “Products” Table Double-clicking the “Store.sdf” database file will open it up within the Server Explorer tab. Since it is a new database there are no tables within it: Right click on the “Tables” icon and choose the “Create Table” menu command to create a new database table. We’ll name the new table “Products” and add 4 columns to it. We’ll mark the first column as a primary key (and make it an identify column so that its value will automatically increment with each new row): When we click “ok” our new Products table will be created in the SQL CE database. Step 4: Populate with Data Once our Products table is created it will show up within the Server Explorer. We can right-click it and choose the “Show Table Data” menu command to edit its data: Let’s add a few sample rows of data to it: Step 5: Create an EF Model Layer We have a SQL CE database with some data in it – let’s now create an EF Model Layer that will provide a way for us to easily query and update data within it. Let’s right-click on our project and choose the “Add->New Item” menu command. This will bring up the “Add New Item” dialog – select the “ADO.NET Entity Data Model” item within it and name it “Store.edmx” This will add a new Store.edmx item to our solution explorer and launch a wizard that allows us to quickly create an EF model: Select the “Generate From Database” option above and click next. Choose to use the Store.sdf SQL CE database we just created and then click next again. The wizard will then ask you what database objects you want to import into your model. Let’s choose to import the “Products” table we created earlier: When we click the “Finish” button Visual Studio will open up the EF designer. It will have a Product entity already on it that maps to the “Products” table within our SQL CE database: The VS 2010 SP1 EF designer works exactly the same with SQL CE as it does already with SQL Server and SQL Express. The Product entity above will be persisted as a class (called “Product”) that we can programmatically work against within our ASP.NET application. Step 6: Compile the Project Before using your model layer you’ll need to build your project. Do a Ctrl+Shift+B to compile the project, or use the Build->Build Solution menu command. Step 7: Create a Page that Uses our EF Model Layer Let’s now create a simple ASP.NET Web Form that contains a GridView control that we can use to display and edit the our Products data (via the EF Model Layer we just created). Right-click on the project and choose the Add->New Item command. Select the “Web Form from Master Page” item template, and name the page you create “Products.aspx”. Base the master page on the “Site.Master” template that is in the root of the project. Add an <h2>Products</h2> heading the new Page, and add an <asp:gridview> control within it: Then click the “Design” tab to switch into design-view. Select the GridView control, and then click the top-right corner to display the GridView’s “Smart Tasks” UI: Choose the “New data source…” drop down option above. This will bring up the below dialog which allows you to pick your Data Source type: Select the “Entity” data source option – which will allow us to easily connect our GridView to the EF model layer we created earlier. This will bring up another dialog that allows us to pick our model layer: Select the “StoreEntities” option in the dropdown – which is the EF model layer we created earlier. Then click next – which will allow us to pick which entity within it we want to bind to: Select the “Products” entity in the above dialog – which indicates that we want to bind against the “Product” entity class we defined earlier. Then click the “Enable automatic updates” checkbox to ensure that we can both query and update Products. When you click “Finish” VS will wire-up an <asp:EntityDataSource> to your <asp:GridView> control: The last two steps we’ll do will be to click the “Enable Editing” checkbox on the Grid (which will cause the Grid to display an “Edit” link on each row) and (optionally) use the Auto Format dialog to pick a UI template for the Grid. Step 8: Run the Application Let’s now run our application and browse to the /Products.aspx page that contains our GridView. When we do so we’ll see a Grid UI of the Products within our SQL CE database. Clicking the “Edit” link for any of the rows will allow us to edit their values: When we click “Update” the GridView will post back the values, persist them through our EF Model Layer, and ultimately save them within our SQL CE database. Learn More about using EF with ASP.NET Web Forms Read this tutorial series on the http://asp.net site to learn more about how to use EF with ASP.NET Web Forms. The tutorial series uses SQL Express as the database – but the nice thing is that all of the same steps/concepts can also now also be done with SQL CE. Walkthrough 2: Using EF Code-First with SQL CE and ASP.NET MVC 3 We used a database-first approach with the sample above – where we first created the database, and then used the EF designer to create model classes from the database. In addition to supporting a designer-based development workflow, EF also enables a more code-centric option which we call “code first development”. Code-First Development enables a pretty sweet development workflow. It enables you to: Define your model objects by simply writing “plain old classes” with no base classes or visual designer required Use a “convention over configuration” approach that enables database persistence without explicitly configuring anything Optionally override the convention-based persistence and use a fluent code API to fully customize the persistence mapping Optionally auto-create a database based on the model classes you define – allowing you to start from code first I’ve done several blog posts about EF Code First in the past – I really think it is great. The good news is that it also works very well with SQL CE. The combination of SQL CE, EF Code First, and the new VS tooling support for SQL CE, enables a pretty nice workflow. Below is a simple example of how you can use them to build a simple ASP.NET MVC 3 application. Step 1: Create a new ASP.NET MVC 3 Project We’ll begin by using the File->New Project menu command within Visual Studio to create a new ASP.NET MVC 3 project. We’ll use the “Internet Project” template so that it has a default UI skin implemented: Step 2: Use NuGet to Install EFCodeFirst Next we’ll use the NuGet package manager (automatically installed by ASP.NET MVC 3) to add the EFCodeFirst library to our project. We’ll use the Package Manager command shell to do this. Bring up the package manager console within Visual Studio by selecting the View->Other Windows->Package Manager Console menu command. Then type: install-package EFCodeFirst within the package manager console to download the EFCodeFirst library and have it be added to our project: When we enter the above command, the EFCodeFirst library will be downloaded and added to our application: Step 3: Build Some Model Classes Using a “code first” based development workflow, we will create our model classes first (even before we have a database). We create these model classes by writing code. For this sample, we will right click on the “Models” folder of our project and add the below three classes to our project: The “Dinner” and “RSVP” model classes above are “plain old CLR objects” (aka POCO). They do not need to derive from any base classes or implement any interfaces, and the properties they expose are standard .NET data-types. No data persistence attributes or data code has been added to them. The “NerdDinners” class derives from the DbContext class (which is supplied by EFCodeFirst) and handles the retrieval/persistence of our Dinner and RSVP instances from a database. Step 4: Listing Dinners We’ve written all of the code necessary to implement our model layer for this simple project. Let’s now expose and implement the URL: /Dinners/Upcoming within our project. We’ll use it to list upcoming dinners that happen in the future. We’ll do this by right-clicking on our “Controllers” folder and select the “Add->Controller” menu command. We’ll name the Controller we want to create “DinnersController”. We’ll then implement an “Upcoming” action method within it that lists upcoming dinners using our model layer above. We will use a LINQ query to retrieve the data and pass it to a View to render with the code below: We’ll then right-click within our Upcoming method and choose the “Add-View” menu command to create an “Upcoming” view template that displays our dinners. We’ll use the “empty” template option within the “Add View” dialog and write the below view template using Razor: Step 4: Configure our Project to use a SQL CE Database We have finished writing all of our code – our last step will be to configure a database connection-string to use. We will point our NerdDinners model class to a SQL CE database by adding the below <connectionString> to the web.config file at the top of our project: EF Code First uses a default convention where context classes will look for a connection-string that matches the DbContext class name. Because we created a “NerdDinners” class earlier, we’ve also named our connectionstring “NerdDinners”. Above we are configuring our connection-string to use SQL CE as the database, and telling it that our SQL CE database file will live within the \App_Data directory of our ASP.NET project. Step 5: Running our Application Now that we’ve built our application, let’s run it! We’ll browse to the /Dinners/Upcoming URL – doing so will display an empty list of upcoming dinners: You might ask – but where did it query to get the dinners from? We didn’t explicitly create a database?!? One of the cool features that EF Code-First supports is the ability to automatically create a database (based on the schema of our model classes) when the database we point it at doesn’t exist. Above we configured EF Code-First to point at a SQL CE database in the \App_Data\ directory of our project. When we ran our application, EF Code-First saw that the SQL CE database didn’t exist and automatically created it for us. Step 6: Using VS 2010 SP1 to Explore our newly created SQL CE Database Click the “Show all Files” icon within the Solution Explorer and you’ll see the “NerdDinners.sdf” SQL CE database file that was automatically created for us by EF code-first within the \App_Data\ folder: We can optionally right-click on the file and “Include in Project" to add it to our solution: We can also double-click the file (regardless of whether it is added to the project) and VS 2010 SP1 will open it as a database we can edit within the “Server Explorer” tab of the IDE. Below is the view we get when we double-click our NerdDinners.sdf SQL CE file. We can drill in to see the schema of the Dinners and RSVPs tables in the tree explorer. Notice how two tables - Dinners and RSVPs – were automatically created for us within our SQL CE database. This was done by EF Code First when we accessed the NerdDinners class by running our application above: We can right-click on a Table and use the “Show Table Data” command to enter some upcoming dinners in our database: We’ll use the built-in editor that VS 2010 SP1 supports to populate our table data below: And now when we hit “refresh” on the /Dinners/Upcoming URL within our browser we’ll see some upcoming dinners show up: Step 7: Changing our Model and Database Schema Let’s now modify the schema of our model layer and database, and walkthrough one way that the new VS 2010 SP1 Tooling support for SQL CE can make this easier. With EF Code-First you typically start making database changes by modifying the model classes. For example, let’s add an additional string property called “UrlLink” to our “Dinner” class. We’ll use this to point to a link for more information about the event: Now when we re-run our project, and visit the /Dinners/Upcoming URL we’ll see an error thrown: We are seeing this error because EF Code-First automatically created our database, and by default when it does this it adds a table that helps tracks whether the schema of our database is in sync with our model classes. EF Code-First helpfully throws an error when they become out of sync – making it easier to track down issues at development time that you might otherwise only find (via obscure errors) at runtime. Note that if you do not want this feature you can turn it off by changing the default conventions of your DbContext class (in this case our NerdDinners class) to not track the schema version. Our model classes and database schema are out of sync in the above example – so how do we fix this? There are two approaches you can use today: Delete the database and have EF Code First automatically re-create the database based on the new model class schema (losing the data within the existing DB) Modify the schema of the existing database to make it in sync with the model classes (keeping/migrating the data within the existing DB) There are a couple of ways you can do the second approach above. Below I’m going to show how you can take advantage of the new VS 2010 SP1 Tooling support for SQL CE to use a database schema tool to modify our database structure. We are also going to be supporting a “migrations” feature with EF in the future that will allow you to automate/script database schema migrations programmatically. Step 8: Modify our SQL CE Database Schema using VS 2010 SP1 The new SQL CE Tooling support within VS 2010 SP1 makes it easy to modify the schema of our existing SQL CE database. To do this we’ll right-click on our “Dinners” table and choose the “Edit Table Schema” command: This will bring up the below “Edit Table” dialog. We can rename, change or delete any of the existing columns in our table, or click at the bottom of the column listing and type to add a new column. Below I’ve added a new “UrlLink” column of type “nvarchar” (since our property is a string): When we click ok our database will be updated to have the new column and our schema will now match our model classes. Because we are manually modifying our database schema, there is one additional step we need to take to let EF Code-First know that the database schema is in sync with our model classes. As i mentioned earlier, when a database is automatically created by EF Code-First it adds a “EdmMetadata” table to the database to track schema versions (and hash our model classes against them to detect mismatches between our model classes and the database schema): Since we are manually updating and maintaining our database schema, we don’t need this table – and can just delete it: This will leave us with just the two tables that correspond to our model classes: And now when we re-run our /Dinners/Upcoming URL it will display the dinners correctly: One last touch we could do would be to update our view to check for the new UrlLink property and render a <a> link to it if an event has one: And now when we refresh our /Dinners/Upcoming we will see hyperlinks for the events that have a UrlLink stored in the database: Summary SQL CE provides a free, embedded, database engine that you can use to easily enable database storage. With SQL CE 4 you can now take advantage of it within ASP.NET projects and applications (both Web Forms and MVC). VS 2010 SP1 provides tooling support that enables you to easily create, edit and modify SQL CE databases – as well as use the standard EF designer against them. This allows you to re-use your existing skills and data knowledge while taking advantage of an embedded database option. This is useful both for small applications (where you don’t need the scalability of a full SQL Server), as well as for development and testing scenarios – where you want to be able to rapidly develop/test your application without having a full database instance. SQL CE makes it easy to later migrate your data to a full SQL Server or SQL Azure instance if you want to – without having to change any code in your application. All we would need to change in the above two scenarios is the <connectionString> value within the web.config file in order to have our code run against a full SQL Server. This provides the flexibility to scale up your application starting from a small embedded database solution as needed. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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Creating a dynamic proxy generator – Part 1 – Creating the Assembly builder, Module builder and cach

- by SeanMcAlinden

I’ve recently started a project with a few mates to learn the ins and outs of Dependency Injection, AOP and a number of other pretty crucial patterns of development as we’ve all been using these patterns for a while but have relied totally on third part solutions to do the magic. We thought it would be interesting to really get into the details by rolling our own IoC container and hopefully learn a lot on the way, and you never know, we might even create an excellent framework. The open source project is called Rapid IoC and is hosted at http://rapidioc.codeplex.com/ One of the most interesting tasks for me is creating the dynamic proxy generator for enabling Aspect Orientated Programming (AOP). In this series of articles, I’m going to track each step I take for creating the dynamic proxy generator and I’ll try my best to explain what everything means - mainly as I’ll be using Reflection.Emit to emit a fair amount of intermediate language code (IL) to create the proxy types at runtime which can be a little taxing to read. It’s worth noting that building the proxy is without a doubt going to be slightly painful so I imagine there will be plenty of areas I’ll need to change along the way. Anyway lets get started… Part 1 - Creating the Assembly builder, Module builder and caching mechanism Part 1 is going to be a really nice simple start, I’m just going to start by creating the assembly, module and type caches. The reason we need to create caches for the assembly, module and types is simply to save the overhead of recreating proxy types that have already been generated, this will be one of the important steps to ensure that the framework is fast… kind of important as we’re calling the IoC container ‘Rapid’ – will be a little bit embarrassing if we manage to create the slowest framework. The Assembly builder The assembly builder is what is used to create an assembly at runtime, we’re going to have two overloads, one will be for the actual use of the proxy generator, the other will be mainly for testing purposes as it will also save the assembly so we can use Reflector to examine the code that has been created. Here’s the code: DynamicAssemblyBuilder using System; using System.Reflection; using System.Reflection.Emit; namespace Rapid.DynamicProxy.Assembly { /// <summary> /// Class for creating an assembly builder. /// </summary> internal static class DynamicAssemblyBuilder { #region Create /// <summary> /// Creates an assembly builder. /// </summary> /// <param name="assemblyName">Name of the assembly.</param> public static AssemblyBuilder Create(string assemblyName) { AssemblyName name = new AssemblyName(assemblyName); AssemblyBuilder assembly = AppDomain.CurrentDomain.DefineDynamicAssembly( name, AssemblyBuilderAccess.Run); DynamicAssemblyCache.Add(assembly); return assembly; } /// <summary> /// Creates an assembly builder and saves the assembly to the passed in location. /// </summary> /// <param name="assemblyName">Name of the assembly.</param> /// <param name="filePath">The file path.</param> public static AssemblyBuilder Create(string assemblyName, string filePath) { AssemblyName name = new AssemblyName(assemblyName); AssemblyBuilder assembly = AppDomain.CurrentDomain.DefineDynamicAssembly( name, AssemblyBuilderAccess.RunAndSave, filePath); DynamicAssemblyCache.Add(assembly); return assembly; } #endregion } } So hopefully the above class is fairly explanatory, an AssemblyName is created using the passed in string for the actual name of the assembly. An AssemblyBuilder is then constructed with the current AppDomain and depending on the overload used, it is either just run in the current context or it is set up ready for saving. It is then added to the cache. DynamicAssemblyCache using System.Reflection.Emit; using Rapid.DynamicProxy.Exceptions; using Rapid.DynamicProxy.Resources.Exceptions; namespace Rapid.DynamicProxy.Assembly { /// <summary> /// Cache for storing the dynamic assembly builder. /// </summary> internal static class DynamicAssemblyCache { #region Declarations private static object syncRoot = new object(); internal static AssemblyBuilder Cache = null; #endregion #region Adds a dynamic assembly to the cache. /// <summary> /// Adds a dynamic assembly builder to the cache. /// </summary> /// <param name="assemblyBuilder">The assembly builder.</param> public static void Add(AssemblyBuilder assemblyBuilder) { lock (syncRoot) { Cache = assemblyBuilder; } } #endregion #region Gets the cached assembly /// <summary> /// Gets the cached assembly builder. /// </summary> /// <returns></returns> public static AssemblyBuilder Get { get { lock (syncRoot) { if (Cache != null) { return Cache; } } throw new RapidDynamicProxyAssertionException(AssertionResources.NoAssemblyInCache); } } #endregion } } The cache is simply a static property that will store the AssemblyBuilder (I know it’s a little weird that I’ve made it public, this is for testing purposes, I know that’s a bad excuse but hey…) There are two methods for using the cache – Add and Get, these just provide thread safe access to the cache. The Module Builder The module builder is required as the create proxy classes will need to live inside a module within the assembly. Here’s the code: DynamicModuleBuilder using System.Reflection.Emit; using Rapid.DynamicProxy.Assembly; namespace Rapid.DynamicProxy.Module { /// <summary> /// Class for creating a module builder. /// </summary> internal static class DynamicModuleBuilder { /// <summary> /// Creates a module builder using the cached assembly. /// </summary> public static ModuleBuilder Create() { string assemblyName = DynamicAssemblyCache.Get.GetName().Name; ModuleBuilder moduleBuilder = DynamicAssemblyCache.Get.DefineDynamicModule (assemblyName, string.Format("{0}.dll", assemblyName)); DynamicModuleCache.Add(moduleBuilder); return moduleBuilder; } } } As you can see, the module builder is created on the assembly that lives in the DynamicAssemblyCache, the module is given the assembly name and also a string representing the filename if the assembly is to be saved. It is then added to the DynamicModuleCache. DynamicModuleCache using System.Reflection.Emit; using Rapid.DynamicProxy.Exceptions; using Rapid.DynamicProxy.Resources.Exceptions; namespace Rapid.DynamicProxy.Module { /// <summary> /// Class for storing the module builder. /// </summary> internal static class DynamicModuleCache { #region Declarations private static object syncRoot = new object(); internal static ModuleBuilder Cache = null; #endregion #region Add /// <summary> /// Adds a dynamic module builder to the cache. /// </summary> /// <param name="moduleBuilder">The module builder.</param> public static void Add(ModuleBuilder moduleBuilder) { lock (syncRoot) { Cache = moduleBuilder; } } #endregion #region Get /// <summary> /// Gets the cached module builder. /// </summary> /// <returns></returns> public static ModuleBuilder Get { get { lock (syncRoot) { if (Cache != null) { return Cache; } } throw new RapidDynamicProxyAssertionException(AssertionResources.NoModuleInCache); } } #endregion } } The DynamicModuleCache is very similar to the assembly cache, it is simply a statically stored module with thread safe Add and Get methods. The DynamicTypeCache To end off this post, I’m going to create the cache for storing the generated proxy classes. I’ve spent a fair amount of time thinking about the type of collection I should use to store the types and have finally decided that for the time being I’m going to use a generic dictionary. This may change when I can actually performance test the proxy generator but the time being I think it makes good sense in theory, mainly as it pretty much maintains it’s performance with varying numbers of items – almost constant (0)1. Plus I won’t ever need to loop through the items which is not the dictionaries strong point. Here’s the code as it currently stands: DynamicTypeCache using System; using System.Collections.Generic; using System.Security.Cryptography; using System.Text; namespace Rapid.DynamicProxy.Types { /// <summary> /// Cache for storing proxy types. /// </summary> internal static class DynamicTypeCache { #region Declarations static object syncRoot = new object(); public static Dictionary<string, Type> Cache = new Dictionary<string, Type>(); #endregion /// <summary> /// Adds a proxy to the type cache. /// </summary> /// <param name="type">The type.</param> /// <param name="proxy">The proxy.</param> public static void AddProxyForType(Type type, Type proxy) { lock (syncRoot) { Cache.Add(GetHashCode(type.AssemblyQualifiedName), proxy); } } /// <summary> /// Tries the type of the get proxy for. /// </summary> /// <param name="type">The type.</param> /// <returns></returns> public static Type TryGetProxyForType(Type type) { lock (syncRoot) { Type proxyType; Cache.TryGetValue(GetHashCode(type.AssemblyQualifiedName), out proxyType); return proxyType; } } #region Private Methods private static string GetHashCode(string fullName) { SHA1CryptoServiceProvider provider = new SHA1CryptoServiceProvider(); Byte[] buffer = Encoding.UTF8.GetBytes(fullName); Byte[] hash = provider.ComputeHash(buffer, 0, buffer.Length); return Convert.ToBase64String(hash); } #endregion } } As you can see, there are two public methods, one for adding to the cache and one for getting from the cache. Hopefully they should be clear enough, the Get is a TryGet as I do not want the dictionary to throw an exception if a proxy doesn’t exist within the cache. Other than that I’ve decided to create a key using the SHA1CryptoServiceProvider, this may change but my initial though is the SHA1 algorithm is pretty fast to put together using the provider and it is also very unlikely to have any hashing collisions. (there are some maths behind how unlikely this is – here’s the wiki if you’re interested http://en.wikipedia.org/wiki/SHA_hash_functions) Anyway, that’s the end of part 1 – although I haven’t started any of the fun stuff (by fun I mean hairpulling, teeth grating Relfection.Emit style fun), I’ve got the basis of the DynamicProxy in place so all we have to worry about now is creating the types, interceptor classes, method invocation information classes and finally a really nice fluent interface that will abstract all of the hard-core craziness away and leave us with a lightning fast, easy to use AOP framework. Hope you find the series interesting. All of the source code can be viewed and/or downloaded at our codeplex site - http://rapidioc.codeplex.com/ Kind Regards, Sean.

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Visual Studio 2010 and .NET 4 Released

- by ScottGu

The final release of Visual Studio 2010 and .NET 4 is now available. Download and Install Today MSDN subscribers, as well as WebsiteSpark/BizSpark/DreamSpark members, can now download the final releases of Visual Studio 2010 and TFS 2010 through the MSDN subscribers download center. If you are not an MSDN Subscriber, you can download free 90-day trial editions of Visual Studio 2010. Or you can can download the free Visual Studio express editions of Visual Web Developer 2010, Visual Basic 2010, Visual C# 2010 and Visual C++. These express editions are available completely for free (and never time out). If you are looking for an easy way to setup a new machine for web-development you can automate installing ASP.NET 4, ASP.NET MVC 2, IIS, SQL Server Express and Visual Web Developer 2010 Express really quickly with the Microsoft Web Platform Installer (just click the install button on the page). What is new with VS 2010 and .NET 4 Today’s release is a big one – and brings with it a ton of new feature and capabilities. One of the things we tried hard to focus on with this release was to invest heavily in making existing applications, projects and developer experiences better. What this means is that you don’t need to read 1000+ page books or spend time learning major new concepts in order to take advantage of the release. There are literally thousands of improvements (both big and small) that make you more productive and successful without having to learn big new concepts in order to start using them. Below is just a small sampling of some of the improvements with this release: Visual Studio 2010 IDE Visual Studio 2010 now supports multiple-monitors (enabling much better use of screen real-estate). It has new code Intellisense support that makes it easier to find and use classes and methods. It has improved code navigation support for searching code-bases and seeing how code is called and used. It has new code visualization support that allows you to see the relationships across projects and classes within projects, as well as to automatically generate sequence diagrams to chart execution flow. The editor now supports HTML and JavaScript snippet support as well as improved JavaScript intellisense. The VS 2010 Debugger and Profiling support is now much, much richer and enables new features like Intellitrace (aka Historical Debugging), debugging of Crash/Dump files, and better parallel debugging. VS 2010’s multi-targeting support is now much richer, and enables you to use VS 2010 to target .NET 2, .NET 3, .NET 3.5 and .NET 4 applications. And the infamous Add Reference dialog now loads much faster. TFS 2010 is now easy to setup (you can now install the server in under 10 minutes) and enables great source-control, bug/work-item tracking, and continuous integration support. Testing (both automated and manual) is now much, much richer. And VS 2010 Premium and Ultimate provide much richer architecture and design tooling support. VB and C# Language Features VB and C# in VS 2010 both contain a bunch of new features and capabilities. VB adds new support for automatic properties, collection initializers, and implicit line continuation support among many other features. C# adds support for optional parameters and named arguments, a new dynamic keyword, co-variance and contra-variance, and among many other features. ASP.NET 4 and ASP.NET MVC 2 With ASP.NET 4, Web Forms controls now render clean, semantically correct, and CSS friendly HTML markup. Built-in URL routing functionality allows you to expose clean, search engine friendly, URLs and increase the traffic to your Website. ViewState within applications can now be more easily controlled and made smaller. ASP.NET Dynamic Data support has been expanded. More controls, including rich charting and data controls, are now built-into ASP.NET 4 and enable you to build applications even faster. New starter project templates now make it easier to get going with new projects. SEO enhancements make it easier to drive traffic to your public facing sites. And web.config files are now clean and simple. ASP.NET MVC 2 is now built-into VS 2010 and ASP.NET 4, and provides a great way to build web sites and applications using a model-view-controller based pattern. ASP.NET MVC 2 adds features to easily enable client and server validation logic, provides new strongly-typed HTML and UI-scaffolding helper methods. It also enables more modular/reusable applications. The new <%: %> syntax in ASP.NET makes it easier to HTML encode output. Visual Studio 2010 also now includes better tooling support for unit testing and TDD. In particular, “Consume first intellisense” and “generate from usage" support within VS 2010 make it easier to write your unit tests first, and then drive your implementation from them. Deploying ASP.NET applications gets a lot easier with this release. You can now publish your Websites and applications to a staging or production server from within Visual Studio itself. Visual Studio 2010 makes it easy to transfer all your files, code, configuration, database schema and data in one complete package. VS 2010 also makes it easy to manage separate web.config configuration files settings depending upon whether you are in debug, release, staging or production modes. WPF 4 and Silverlight 4 WPF 4 includes a ton of new improvements and capabilities including more built-in controls, richer graphics features (cached composition, pixel shader 3 support, layoutrounding, and animation easing functions), a much improved text stack (with crisper text rendering, custom dictionary support, and selection and caret brush options). WPF 4 also includes a bunch of support to enable you to take advantage of new Windows 7 features – including multi-touch and Windows 7 shell integration. Silverlight 4 will launch this week as well. You can watch my Silverlight 4 launch keynote streamed live Tuesday (April 13th) at 8am Pacific Time. Silverlight 4 includes a ton of new capabilities – including a bunch for making it possible to build great business applications and out of the browser applications. I’ll be doing a separate blog post later this week (once it is live on the web) that talks more about its capabilities. Visual Studio 2010 now includes great tooling support for both WPF and Silverlight. The new VS 2010 WPF and Silverlight designer makes it much easier to build client applications as well as build great line of business solutions, as well as integrate and bind with data. Tooling support for Silverlight 4 with the final release of Visual Studio 2010 will be available when Silverlight 4 releases to the web this week. SharePoint and Azure Visual Studio 2010 now includes built-in support for building SharePoint applications. You can now create, edit, build, and debug SharePoint applications directly within Visual Studio 2010. You can also now use SharePoint with TFS 2010. Support for creating Azure-hosted applications is also now included with VS 2010 – allowing you to build ASP.NET and WCF based applications and host them within the cloud. Data Access Data access has a lot of improvements coming to it with .NET 4. Entity Framework 4 includes a ton of new features and capabilities – including support for model first and POCO development, default support for lazy loading, built-in support for pluralization/singularization of table/property names within the VS 2010 designer, full support for all the LINQ operators, the ability to optionally expose foreign keys on model objects (useful for some stateless web scenarios), disconnected API support to better handle N-Tier and stateless web scenarios, and T4 template customization support within VS 2010 to allow you to customize and automate how code is generated for you by the data designer. In addition to improvements with the Entity Framework, LINQ to SQL with .NET 4 also includes a bunch of nice improvements. WCF and Workflow WCF includes a bunch of great new capabilities – including better REST, activation and configuration support. WCF Data Services (formerly known as Astoria) and WCF RIA Services also now enable you to easily expose and work with data from remote clients. Windows Workflow is now much faster, includes flowchart services, and now makes it easier to make custom services than before. More details can be found here. CLR and Core .NET Library Improvements .NET 4 includes the new CLR 4 engine – which includes a lot of nice performance and feature improvements. CLR 4 engine now runs side-by-side in-process with older versions of the CLR – allowing you to use two different versions of .NET within the same process. It also includes improved COM interop support. The .NET 4 base class libraries (BCL) include a bunch of nice additions and refinements. In particular, the .NET 4 BCL now includes new parallel programming support that makes it much easier to build applications that take advantage of multiple CPUs and cores on a computer. This work dove-tails nicely with the new VS 2010 parallel debugger (making it much easier to debug parallel applications), as well as the new F# functional language support now included in the VS 2010 IDE. .NET 4 also now also has the Dynamic Language Runtime (DLR) library built-in – which makes it easier to use dynamic language functionality with .NET. MEF – a really cool library that enables rich extensibility – is also now built-into .NET 4 and included as part of the base class libraries. .NET 4 Client Profile The download size of the .NET 4 redist is now much smaller than it was before (the x86 full .NET 4 package is about 36MB). We also now have a .NET 4 Client Profile package which is a pure sub-set of the full .NET that can be used to streamline client application installs. C++ VS 2010 includes a bunch of great improvements for C++ development. This includes better C++ Intellisense support, MSBuild support for projects, improved parallel debugging and profiler support, MFC improvements, and a number of language features and compiler optimizations. My VS 2010 and .NET 4 Blog Series I’ve been cranking away on a blog series the last few months that highlights many of the new VS 2010 and .NET 4 improvements. The good news is that I have about 20 in-depth posts already written. The bad news (for me) is that I have about 200 more to go until I’m done! I’m going to try and keep adding a few more each week over the next few months to discuss the new improvements and how best to take advantage of them. Below is a list of the already written ones that you can check out today: Clean Web.Config Files Starter Project Templates Multi-targeting Multiple Monitor Support New Code Focused Web Profile Option HTML / ASP.NET / JavaScript Code Snippets Auto-Start ASP.NET Applications URL Routing with ASP.NET 4 Web Forms Searching and Navigating Code in VS 2010 VS 2010 Code Intellisense Improvements WPF 4 Add Reference Dialog Improvements SEO Improvements with ASP.NET 4 Output Cache Extensibility with ASP.NET 4 Built-in Charting Controls for ASP.NET and Windows Forms Cleaner HTML Markup with ASP.NET 4 - Client IDs Optional Parameters and Named Arguments in C# 4 - and a cool scenarios with ASP.NET MVC 2 Automatic Properties, Collection Initializers and Implicit Line Continuation Support with VB 2010 New <%: %> Syntax for HTML Encoding Output using ASP.NET 4 JavaScript Intellisense Improvements with VS 2010 Stay tuned to my blog as I post more. Also check out this page which links to a bunch of great articles and videos done by others. VS 2010 Installation Notes If you have installed a previous version of VS 2010 on your machine (either the beta or the RC) you must first uninstall it before installing the final VS 2010 release. I also recommend uninstalling .NET 4 betas (including both the client and full .NET 4 installs) as well as the other installs that come with VS 2010 (e.g. ASP.NET MVC 2 preview builds, etc). The uninstalls of the betas/RCs will clean up all the old state on your machine – after which you can install the final VS 2010 version and should have everything just work (this is what I’ve done on all of my machines and I haven’t had any problems). The VS 2010 and .NET 4 installs add a bunch of new managed assemblies to your machine. Some of these will be “NGEN’d” to native code during the actual install process (making them run fast). To avoid adding too much time to VS setup, though, we don’t NGEN all assemblies immediately – and instead will NGEN the rest in the background when your machine is idle. Until it finishes NGENing the assemblies they will be JIT’d to native code the first time they are used in a process – which for large assemblies can sometimes cause a slight performance hit. If you run into this you can manually force all assemblies to be NGEN’d to native code immediately (and not just wait till the machine is idle) by launching the Visual Studio command line prompt from the Windows Start Menu (Microsoft Visual Studio 2010->Visual Studio Tools->Visual Studio Command Prompt). Within the command prompt type “Ngen executequeueditems” – this will cause everything to be NGEN’d immediately. How to Buy Visual Studio 2010 You can can download and use the free Visual Studio express editions of Visual Web Developer 2010, Visual Basic 2010, Visual C# 2010 and Visual C++. These express editions are available completely for free (and never time out). You can buy a new copy of VS 2010 Professional that includes a 1 year subscription to MSDN Essentials for $799. MSDN Essentials includes a developer license of Windows 7 Ultimate, Windows Server 2008 R2 Enterprise, SQL Server 2008 DataCenter R2, and 20 hours of Azure hosting time. Subscribers also have access to MSDN’s Online Concierge, and Priority Support in MSDN Forums. Upgrade prices from previous releases of Visual Studio are also available. Existing Visual Studio 2005/2008 Standard customers can upgrade to Visual Studio 2010 Professional for a special $299 retail price until October. You can take advantage of this VS Standard->Professional upgrade promotion here. Web developers who build applications for others, and who are either independent developers or who work for companies with less than 10 employees, can also optionally take advantage of the Microsoft WebSiteSpark program. This program gives you three copies of Visual Studio 2010 Professional, 1 copy of Expression Studio, and 4 CPU licenses of both Windows 2008 R2 Web Server and SQL 2008 Web Edition that you can use to both develop and deploy applications with at no cost for 3 years. At the end of the 3 years there is no obligation to buy anything. You can sign-up for WebSiteSpark today in under 5 minutes – and immediately have access to the products to download. Summary Today’s release is a big one – and has a bunch of improvements for pretty much every developer. Thank you everyone who provided feedback, suggestions and reported bugs throughout the development process – we couldn’t have delivered it without you. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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A Taxonomy of Numerical Methods v1

- by JoshReuben

Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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Announcing the release of the Windows Azure SDK 2.1 for .NET

- by ScottGu

Today we released the v2.1 update of the Windows Azure SDK for .NET. This is a major refresh of the Windows Azure SDK and it includes some great new features and enhancements. These new capabilities include: Visual Studio 2013 Preview Support: The Windows Azure SDK now supports using the new VS 2013 Preview Visual Studio 2013 VM Image: Windows Azure now has a built-in VM image that you can use to host and develop with VS 2013 in the cloud Visual Studio Server Explorer Enhancements: Redesigned with improved filtering and auto-loading of subscription resources Virtual Machines: Start and Stop VM’s w/suspend billing directly from within Visual Studio Cloud Services: New Emulator Express option with reduced footprint and Run as Normal User support Service Bus: New high availability options, Notification Hub support, Improved VS tooling PowerShell Automation: Lots of new PowerShell commands for automating Web Sites, Cloud Services, VMs and more All of these SDK enhancements are now available to start using immediately and you can download the SDK from the Windows Azure .NET Developer Center. Visual Studio’s Team Foundation Service (http://tfs.visualstudio.com/) has also been updated to support today’s SDK 2.1 release, and the SDK 2.1 features can now be used with it (including with automated builds + tests). Below are more details on the new features and capabilities released today: Visual Studio 2013 Preview Support Today’s Window Azure SDK 2.1 release adds support for the recent Visual Studio 2013 Preview. The 2.1 SDK also works with Visual Studio 2010 and Visual Studio 2012, and works side by side with the previous Windows Azure SDK 1.8 and 2.0 releases. To install the Windows Azure SDK 2.1 on your local computer, choose the “install the sdk” link from the Windows Azure .NET Developer Center. Then, chose which version of Visual Studio you want to use it with. Clicking the third link will install the SDK with the latest VS 2013 Preview: If you don’t already have the Visual Studio 2013 Preview installed on your machine, this will also install Visual Studio Express 2013 Preview for Web. Visual Studio 2013 VM Image Hosted in the Cloud One of the requests we’ve heard from several customers has been to have the ability to host Visual Studio within the cloud (avoiding the need to install anything locally on your computer). With today’s SDK update we’ve added a new VM image to the Windows Azure VM Gallery that has Visual Studio Ultimate 2013 Preview, SharePoint 2013, SQL Server 2012 Express and the Windows Azure 2.1 SDK already installed on it. This provides a really easy way to create a development environment in the cloud with the latest tools. With the recent shutdown and suspend billing feature we shipped on Windows Azure last month, you can spin up the image only when you want to do active development, and then shut down the virtual machine and not have to worry about usage charges while the virtual machine is not in use. You can create your own VS image in the cloud by using the New->Compute->Virtual Machine->From Gallery menu within the Windows Azure Management Portal, and then by selecting the “Visual Studio Ultimate 2013 Preview” template: Visual Studio Server Explorer: Improved Filtering/Management of Subscription Resources With the Windows Azure SDK 2.1 release you’ll notice significant improvements in the Visual Studio Server Explorer. The explorer has been redesigned so that all Windows Azure services are now contained under a single Windows Azure node. From the top level node you can now manage your Windows Azure credentials, import a subscription file or filter Server Explorer to only show services from particular subscriptions or regions. Note: The Web Sites and Mobile Services nodes will appear outside the Windows Azure Node until the final release of VS 2013. If you have installed the ASP.NET and Web Tools Preview Refresh, though, the Web Sites node will appear inside the Windows Azure node even with the VS 2013 Preview. Once your subscription information is added, Windows Azure services from all your subscriptions are automatically enumerated in the Server Explorer. You no longer need to manually add services to Server Explorer individually. This provides a convenient way of viewing all of your cloud services, storage accounts, service bus namespaces, virtual machines, and web sites from one location: Subscription and Region Filtering Support Using the Windows Azure node in Server Explorer, you can also now filter your Windows Azure services in the Server Explorer by the subscription or region they are in. If you have multiple subscriptions but need to focus your attention to just a few subscription for some period of time, this a handy way to hide the services from other subscriptions view until they become relevant. You can do the same sort of filtering by region. To enable this, just select “Filter Services” from the context menu on the Windows Azure node: Then choose the subscriptions and/or regions you want to filter by. In the below example, I’ve decided to show services from my pay-as-you-go subscription within the East US region: Visual Studio will then automatically filter the items that show up in the Server Explorer appropriately: With storage accounts and service bus namespaces, you sometimes need to work with services outside your subscription. To accommodate that scenario, those services allow you to attach an external account (from the context menu). You’ll notice that external accounts have a slightly different icon in server explorer to indicate they are from outside your subscription. Other Improvements We’ve also improved the Server Explorer by adding additional properties and actions to the service exposed. You now have access to most of the properties on a cloud service, deployment slot, role or role instance as well as the properties on storage accounts, virtual machines and web sites. Just select the object of interest in Server Explorer and view the properties in the property pane. We also now have full support for creating/deleting/update storage tables, blobs and queues from directly within Server Explorer. Simply right-click on the appropriate storage account node and you can create them directly within Visual Studio: Virtual Machines: Start/Stop within Visual Studio Virtual Machines now have context menu actions that allow you start, shutdown, restart and delete a Virtual Machine directly within the Visual Studio Server Explorer. The shutdown action enables you to shut down the virtual machine and suspend billing when the VM is not is use, and easily restart it when you need it: This is especially useful in Dev/Test scenarios where you can start a VM – such as a SQL Server – during your development session and then shut it down / suspend billing when you are not developing (and no longer be billed for it). You can also now directly remote desktop into VMs using the “Connect using Remote Desktop” context menu command in VS Server Explorer. Cloud Services: Emulator Express with Run as Normal User Support You can now launch Visual Studio and run your cloud services locally as a Normal User (without having to elevate to an administrator account) using a new Emulator Express option included as a preview feature with this SDK release. Emulator Express is a version of the Windows Azure Compute Emulator that runs a restricted mode – one instance per role – and it doesn’t require administrative permissions and uses 40% less resources than the full Windows Azure Emulator. Emulator Express supports both web and worker roles. To run your application locally using the Emulator Express option, simply change the following settings in the Windows Azure project. On the shortcut menu for the Windows Azure project, choose Properties, and then choose the Web tab. Check the setting for IIS (Internet Information Services). Make sure that the option is set to IIS Express, not the full version of IIS. Emulator Express is not compatible with full IIS. On the Web tab, choose the option for Emulator Express. Service Bus: Notification Hubs With the Windows Azure SDK 2.1 release we are adding support for Windows Azure Notification Hubs as part of our official Windows Azure SDK, inside of Microsoft.ServiceBus.dll (previously the Notification Hub functionality was in a preview assembly). You are now able to create, update and delete Notification Hubs programmatically, manage your device registrations, and send push notifications to all your mobile clients across all platforms (Windows Store, Windows Phone 8, iOS, and Android). Learn more about Notification Hubs on MSDN here, or watch the Notification Hubs //BUILD/ presentation here. Service Bus: Paired Namespaces One of the new features included with today’s Windows Azure SDK 2.1 release is support for Service Bus “Paired Namespaces”. Paired Namespaces enable you to better handle situations where a Service Bus service namespace becomes unavailable (for example: due to connectivity issues or an outage) and you are unable to send or receive messages to the namespace hosting the queue, topic, or subscription. Previously,to handle this scenario you had to manually setup separate namespaces that can act as a backup, then implement manual failover and retry logic which was sometimes tricky to get right. Service Bus now supports Paired Namespaces, which enables you to connect two namespaces together. When you activate the secondary namespace, messages are stored in the secondary queue for delivery to the primary queue at a later time. If the primary container (namespace) becomes unavailable for some reason, automatic failover enables the messages in the secondary queue. For detailed information about paired namespaces and high availability, see the new topic Asynchronous Messaging Patterns and High Availability. Service Bus: Tooling Improvements In this release, the Windows Azure Tools for Visual Studio contain several enhancements and changes to the management of Service Bus messaging entities using Visual Studio’s Server Explorer. The most noticeable change is that the Service Bus node is now integrated into the Windows Azure node, and supports integrated subscription management. Additionally, there has been a change to the code generated by the Windows Azure Worker Role with Service Bus Queue project template. This code now uses an event-driven “message pump” programming model using the QueueClient.OnMessage method. PowerShell: Tons of New Automation Commands Since my last blog post on the previous Windows Azure SDK 2.0 release, we’ve updated Windows Azure PowerShell (which is a separate download) five times. You can find the full change log here. We’ve added new cmdlets in the following areas: China instance and Windows Azure Pack support Environment Configuration VMs Cloud Services Web Sites Storage SQL Azure Service Bus China Instance and Windows Azure Pack We now support the following cmdlets for the China instance and Windows Azure Pack, respectively: China Instance: Web Sites, Service Bus, Storage, Cloud Service, VMs, Network Windows Azure Pack: Web Sites, Service Bus We will have full cmdlet support for these two Windows Azure environments in PowerShell in the near future. Virtual Machines: Stop/Start Virtual Machines Similar to the Start/Stop VM capability in VS Server Explorer, you can now stop your VM and suspend billing: If you want to keep the original behavior of keeping your stopped VM provisioned, you can pass in the -StayProvisioned switch parameter. Virtual Machines: VM endpoint ACLs We’ve added and updated a bunch of cmdlets for you to configure fine-grained network ACL on your VM endpoints. You can use the following cmdlets to create ACL config and apply them to a VM endpoint: New-AzureAclConfig Get-AzureAclConfig Set-AzureAclConfig Remove-AzureAclConfig Add-AzureEndpoint -ACL Set-AzureEndpoint –ACL The following example shows how to add an ACL rule to an existing endpoint of a VM. Other improvements for Virtual Machine management includes Added -NoWinRMEndpoint parameter to New-AzureQuickVM and Add-AzureProvisioningConfig to disable Windows Remote Management Added -DirectServerReturn parameter to Add-AzureEndpoint and Set-AzureEndpoint to enable/disable direct server return Added Set-AzureLoadBalancedEndpoint cmdlet to modify load balanced endpoints Cloud Services: Remote Desktop and Diagnostics Remote Desktop and Diagnostics are popular debugging options for Cloud Services. We’ve introduced cmdlets to help you configure these two Cloud Service extensions from Windows Azure PowerShell. Windows Azure Cloud Services Remote Desktop extension: New-AzureServiceRemoteDesktopExtensionConfig Get-AzureServiceRemoteDesktopExtension Set-AzureServiceRemoteDesktopExtension Remove-AzureServiceRemoteDesktopExtension Windows Azure Cloud Services Diagnostics extension New-AzureServiceDiagnosticsExtensionConfig Get-AzureServiceDiagnosticsExtension Set-AzureServiceDiagnosticsExtension Remove-AzureServiceDiagnosticsExtension The following example shows how to enable Remote Desktop for a Cloud Service. Web Sites: Diagnostics With our last SDK update, we introduced the Get-AzureWebsiteLog –Tail cmdlet to get the log streaming of your Web Sites. Recently, we’ve also added cmdlets to configure Web Site application diagnostics: Enable-AzureWebsiteApplicationDiagnostic Disable-AzureWebsiteApplicationDiagnostic The following 2 examples show how to enable application diagnostics to the file system and a Windows Azure Storage Table: SQL Database Previously, you had to know the SQL Database server admin username and password if you want to manage the database in that SQL Database server. Recently, we’ve made the experience much easier by not requiring the admin credential if the database server is in your subscription. So you can simply specify the -ServerName parameter to tell Windows Azure PowerShell which server you want to use for the following cmdlets. Get-AzureSqlDatabase New-AzureSqlDatabase Remove-AzureSqlDatabase Set-AzureSqlDatabase We’ve also added a -AllowAllAzureServices parameter to New-AzureSqlDatabaseServerFirewallRule so that you can easily add a firewall rule to whitelist all Windows Azure IP addresses. Besides the above experience improvements, we’ve also added cmdlets get the database server quota and set the database service objective. Check out the following cmdlets for details. Get-AzureSqlDatabaseServerQuota Get-AzureSqlDatabaseServiceObjective Set-AzureSqlDatabase –ServiceObjective Storage and Service Bus Other new cmdlets include Storage: CRUD cmdlets for Azure Tables and Queues Service Bus: Cmdlets for managing authorization rules on your Service Bus Namespace, Queue, Topic, Relay and NotificationHub Summary Today’s release includes a bunch of great features that enable you to build even better cloud solutions. All the above features/enhancements are shipped and available to use immediately as part of the 2.1 release of the Windows Azure SDK for .NET. If you don’t already have a Windows Azure account, you can sign-up for a free trial and start using all of the above features today. Then visit the Windows Azure Developer Center to learn more about how to build apps with it. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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Diving into OpenStack Network Architecture - Part 1

- by Ronen Kofman

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In this blog series we will review an existing OpenStack setup using the Oracle OpenStack Tech Preview and explain the different network components through use cases and examples. The goal is to show how the different pieces come together and provide a bigger picture view of the network architecture in OpenStack. This can be very helpful to users making their first steps in OpenStack or anyone wishes to understand how networking works in this environment. We will go through the basics first and build the examples as we go. According to the recent Icehouse user survey and the one before it, Neutron with Open vSwitch plug-in is the most widely used network setup both in production and in POCs (in terms of number of customers) and so in this blog series we will analyze this specific OpenStack networking setup. As we know there are many options to setup OpenStack networking and while Neturon + Open vSwitch is the most popular setup there is no claim that it is either best or the most efficient option. Neutron + Open vSwitch is an example, one which provides a good starting point for anyone interested in understanding OpenStack networking. Even if you are using different kind of network setup such as different Neutron plug-in or even not using Neutron at all this will still be a good starting point to understand the network architecture in OpenStack. The setup we are using for the examples is the one used in the Oracle OpenStack Tech Preview. Installing it is simple and it would be helpful to have it as reference. In this setup we use eth2 on all servers for VM network, all VM traffic will be flowing through this interface.The Oracle OpenStack Tech Preview is using VLANs for L2 isolation to provide tenant and network isolation. The following diagram shows how we have configured our deployment: This first post is a bit long and will focus on some basic concepts in OpenStack networking. The components we will be discussing are Open vSwitch, network namespaces, Linux bridge and veth pairs. Note that this is not meant to be a comprehensive review of these components, it is meant to describe the component as much as needed to understand OpenStack network architecture. All the components described here can be further explored using other resources. Open vSwitch (OVS) In the Oracle OpenStack Tech Preview OVS is used to connect virtual machines to the physical port (in our case eth2) as shown in the deployment diagram. OVS contains bridges and ports, the OVS bridges are different from the Linux bridge (controlled by the brctl command) which are also used in this setup. To get started let’s view the OVS structure, use the following command: # ovs-vsctl show 7ec51567-ab42-49e8-906d-b854309c9edf Bridge br-int Port br-int Interface br-int type: internal Port "int-br-eth2" Interface "int-br-eth2" Bridge "br-eth2" Port "br-eth2" Interface "br-eth2" type: internal Port "eth2" Interface "eth2" Port "phy-br-eth2" Interface "phy-br-eth2" ovs_version: "1.11.0" We see a standard post deployment OVS on a compute node with two bridges and several ports hanging off of each of them. The example above is a compute node without any VMs, we can see that the physical port eth2 is connected to a bridge called “br-eth2”. We also see two ports "int-br-eth2" and "phy-br-eth2" which are actually a veth pair and form virtual wire between the two bridges, veth pairs are discussed later in this post. When a virtual machine is created a port is created on one the br-int bridge and this port is eventually connected to the virtual machine (we will discuss the exact connectivity later in the series). Here is how OVS looks after a VM was launched: # ovs-vsctl show efd98c87-dc62-422d-8f73-a68c2a14e73d Bridge br-int Port "int-br-eth2" Interface "int-br-eth2" Port br-int Interface br-int type: internal Port "qvocb64ea96-9f" tag: 1 Interface "qvocb64ea96-9f" Bridge "br-eth2" Port "phy-br-eth2" Interface "phy-br-eth2" Port "br-eth2" Interface "br-eth2" type: internal Port "eth2" Interface "eth2" ovs_version: "1.11.0" Bridge "br-int" now has a new port "qvocb64ea96-9f" which connects to the VM and tagged with VLAN 1. Every VM which will be launched will add a port on the “br-int” bridge for every network interface the VM has. Another useful command on OVS is dump-flows for example: # ovs-ofctl dump-flows br-int NXST_FLOW reply (xid=0x4): cookie=0x0, duration=735.544s, table=0, n_packets=70, n_bytes=9976, idle_age=17, priority=3,in_port=1,dl_vlan=1000 actions=mod_vlan_vid:1,NORMAL cookie=0x0, duration=76679.786s, table=0, n_packets=0, n_bytes=0, idle_age=65534, hard_age=65534, priority=2,in_port=1 actions=drop cookie=0x0, duration=76681.36s, table=0, n_packets=68, n_bytes=7950, idle_age=17, hard_age=65534, priority=1 actions=NORMAL As we see the port which is connected to the VM has the VLAN tag 1. However the port on the VM network (eth2) will be using tag 1000. OVS is modifying the vlan as the packet flow from the VM to the physical interface. In OpenStack the Open vSwitch agent takes care of programming the flows in Open vSwitch so the users do not have to deal with this at all. If you wish to learn more about how to program the Open vSwitch you can read more about it at http://openvswitch.org looking at the documentation describing the ovs-ofctl command. Network Namespaces (netns) Network namespaces is a very cool Linux feature can be used for many purposes and is heavily used in OpenStack networking. Network namespaces are isolated containers which can hold a network configuration and is not seen from outside of the namespace. A network namespace can be used to encapsulate specific network functionality or provide a network service in isolation as well as simply help to organize a complicated network setup. Using the Oracle OpenStack Tech Preview we are using the latest Unbreakable Enterprise Kernel R3 (UEK3), this kernel provides a complete support for netns. Let's see how namespaces work through couple of examples to control network namespaces we use the ip netns command: Defining a new namespace: # ip netns add my-ns # ip netns list my-ns As mentioned the namespace is an isolated container, we can perform all the normal actions in the namespace context using the exec command for example running the ifconfig command: # ip netns exec my-ns ifconfig -a lo Link encap:Local Loopback LOOPBACK MTU:16436 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) We can run every command in the namespace context, this is especially useful for debug using tcpdump command, we can ping or ssh or define iptables all within the namespace. Connecting the namespace to the outside world: There are various ways to connect into a namespaces and between namespaces we will focus on how this is done in OpenStack. OpenStack uses a combination of Open vSwitch and network namespaces. OVS defines the interfaces and then we can add those interfaces to namespace. So first let's add a bridge to OVS: # ovs-vsctl add-br my-bridge Now let's add a port on the OVS and make it internal: # ovs-vsctl add-port my-bridge my-port # ovs-vsctl set Interface my-port type=internal And let's connect it into the namespace: # ip link set my-port netns my-ns Looking inside the namespace: # ip netns exec my-ns ifconfig -a lo Link encap:Local Loopback LOOPBACK MTU:65536 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) my-port Link encap:Ethernet HWaddr 22:04:45:E2:85:21 BROADCAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) Now we can add more ports to the OVS bridge and connect it to other namespaces or other device like physical interfaces. Neutron is using network namespaces to implement network services such as DCHP, routing, gateway, firewall, load balance and more. In the next post we will go into this in further details. Linux Bridge and veth pairs Linux bridge is used to connect the port from OVS to the VM. Every port goes from the OVS bridge to a Linux bridge and from there to the VM. The reason for using regular Linux bridges is for security groups’ enforcement. Security groups are implemented using iptables and iptables can only be applied to Linux bridges and not to OVS bridges. Veth pairs are used extensively throughout the network setup in OpenStack and are also a good tool to debug a network problem. Veth pairs are simply a virtual wire and so veths always come in pairs. Typically one side of the veth pair will connect to a bridge and the other side to another bridge or simply left as a usable interface. In this example we will create some veth pairs, connect them to bridges and test connectivity. This example is using regular Linux server and not an OpenStack node: Creating a veth pair, note that we define names for both ends: # ip link add veth0 type veth peer name veth1 # ifconfig -a . . veth0 Link encap:Ethernet HWaddr 5E:2C:E6:03:D0:17 BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) veth1 Link encap:Ethernet HWaddr E6:B6:E2:6D:42:B8 BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) . . To make the example more meaningful this we will create the following setup: veth0 => veth1 => br-eth3 => eth3 ======> eth2 on another Linux server br-eth3 – a regular Linux bridge which will be connected to veth1 and eth3 eth3 – a physical interface with no IP on it, connected to a private network eth2 – a physical interface on the remote Linux box connected to the private network and configured with the IP of 50.50.50.1 Once we create the setup we will ping 50.50.50.1 (the remote IP) through veth0 to test that the connection is up: # brctl addbr br-eth3 # brctl addif br-eth3 eth3 # brctl addif br-eth3 veth1 # brctl show bridge name bridge id STP enabled interfaces br-eth3 8000.00505682e7f6 no eth3 veth1 # ifconfig veth0 50.50.50.50 # ping -I veth0 50.50.50.51 PING 50.50.50.51 (50.50.50.51) from 50.50.50.50 veth0: 56(84) bytes of data. 64 bytes from 50.50.50.51: icmp_seq=1 ttl=64 time=0.454 ms 64 bytes from 50.50.50.51: icmp_seq=2 ttl=64 time=0.298 ms When the naming is not as obvious as the previous example and we don't know who are the paired veth interfaces we can use the ethtool command to figure this out. The ethtool command returns an index we can look up using ip link command, for example: # ethtool -S veth1 NIC statistics: peer_ifindex: 12 # ip link . . 12: veth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 Summary That’s all for now, we quickly reviewed OVS, network namespaces, Linux bridges and veth pairs. These components are heavily used in the OpenStack network architecture we are exploring and understanding them well will be very useful when reviewing the different use cases. In the next post we will look at how the OpenStack network is laid out connecting the virtual machines to each other and to the external world. @RonenKofman

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When is a SQL function not a function?

- by Rob Farley

Should SQL Server even have functions? (Oh yeah – this is a T-SQL Tuesday post, hosted this month by Brad Schulz) Functions serve an important part of programming, in almost any language. A function is a piece of code that is designed to return something, as opposed to a piece of code which isn’t designed to return anything (which is known as a procedure). SQL Server is no different. You can call stored procedures, even from within other stored procedures, and you can call functions and use these in other queries. Stored procedures might query something, and therefore ‘return data’, but a function in SQL is considered to have the type of the thing returned, and can be used accordingly in queries. Consider the internal GETDATE() function. SELECT GETDATE(), SomeDatetimeColumn FROM dbo.SomeTable; There’s no logical difference between the field that is being returned by the function and the field that’s being returned by the table column. Both are the datetime field – if you didn’t have inside knowledge, you wouldn’t necessarily be able to tell which was which. And so as developers, we find ourselves wanting to create functions that return all kinds of things – functions which look up values based on codes, functions which do string manipulation, and so on. But it’s rubbish. Ok, it’s not all rubbish, but it mostly is. And this isn’t even considering the SARGability impact. It’s far more significant than that. (When I say the SARGability aspect, I mean “because you’re unlikely to have an index on the result of some function that’s applied to a column, so try to invert the function and query the column in an unchanged manner”) I’m going to consider the three main types of user-defined functions in SQL Server: Scalar Inline Table-Valued Multi-statement Table-Valued I could also look at user-defined CLR functions, including aggregate functions, but not today. I figure that most people don’t tend to get around to doing CLR functions, and I’m going to focus on the T-SQL-based user-defined functions. Most people split these types of function up into two types. So do I. Except that most people pick them based on ‘scalar or table-valued’. I’d rather go with ‘inline or not’. If it’s not inline, it’s rubbish. It really is. Let’s start by considering the two kinds of table-valued function, and compare them. These functions are going to return the sales for a particular salesperson in a particular year, from the AdventureWorks database. CREATE FUNCTION dbo.FetchSales_inline(@salespersonid int, @orderyear int) RETURNS TABLE AS RETURN ( SELECT e.LoginID as EmployeeLogin, o.OrderDate, o.SalesOrderID FROM Sales.SalesOrderHeader AS o LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = o.SalesPersonID WHERE o.SalesPersonID = @salespersonid AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101') AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101') ) ; GO CREATE FUNCTION dbo.FetchSales_multi(@salespersonid int, @orderyear int) RETURNS @results TABLE ( EmployeeLogin nvarchar(512), OrderDate datetime, SalesOrderID int ) AS BEGIN INSERT @results (EmployeeLogin, OrderDate, SalesOrderID) SELECT e.LoginID, o.OrderDate, o.SalesOrderID FROM Sales.SalesOrderHeader AS o LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = o.SalesPersonID WHERE o.SalesPersonID = @salespersonid AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101') AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101') ; RETURN END ; GO You’ll notice that I’m being nice and responsible with the use of the DATEADD function, so that I have SARGability on the OrderDate filter. Regular readers will be hoping I’ll show what’s going on in the execution plans here. Here I’ve run two SELECT * queries with the “Show Actual Execution Plan” option turned on. Notice that the ‘Query cost’ of the multi-statement version is just 2% of the ‘Batch cost’. But also notice there’s trickery going on. And it’s nothing to do with that extra index that I have on the OrderDate column. Trickery. Look at it – clearly, the first plan is showing us what’s going on inside the function, but the second one isn’t. The second one is blindly running the function, and then scanning the results. There’s a Sequence operator which is calling the TVF operator, and then calling a Table Scan to get the results of that function for the SELECT operator. But surely it still has to do all the work that the first one is doing... To see what’s actually going on, let’s look at the Estimated plan. Now, we see the same plans (almost) that we saw in the Actuals, but we have an extra one – the one that was used for the TVF. Here’s where we see the inner workings of it. You’ll probably recognise the right-hand side of the TVF’s plan as looking very similar to the first plan – but it’s now being called by a stack of other operators, including an INSERT statement to be able to populate the table variable that the multi-statement TVF requires. And the cost of the TVF is 57% of the batch! But it gets worse. Let’s consider what happens if we don’t need all the columns. We’ll leave out the EmployeeLogin column. Here, we see that the inline function call has been simplified down. It doesn’t need the Employee table. The join is redundant and has been eliminated from the plan, making it even cheaper. But the multi-statement plan runs the whole thing as before, only removing the extra column when the Table Scan is performed. A multi-statement function is a lot more powerful than an inline one. An inline function can only be the result of a single sub-query. It’s essentially the same as a parameterised view, because views demonstrate this same behaviour of extracting the definition of the view and using it in the outer query. A multi-statement function is clearly more powerful because it can contain far more complex logic. But a multi-statement function isn’t really a function at all. It’s a stored procedure. It’s wrapped up like a function, but behaves like a stored procedure. It would be completely unreasonable to expect that a stored procedure could be simplified down to recognise that not all the columns might be needed, but yet this is part of the pain associated with this procedural function situation. The biggest clue that a multi-statement function is more like a stored procedure than a function is the “BEGIN” and “END” statements that surround the code. If you try to create a multi-statement function without these statements, you’ll get an error – they are very much required. When I used to present on this kind of thing, I even used to call it “The Dangers of BEGIN and END”, and yes, I’ve written about this type of thing before in a similarly-named post over at my old blog. Now how about scalar functions... Suppose we wanted a scalar function to return the count of these. CREATE FUNCTION dbo.FetchSales_scalar(@salespersonid int, @orderyear int) RETURNS int AS BEGIN RETURN ( SELECT COUNT(*) FROM Sales.SalesOrderHeader AS o LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = o.SalesPersonID WHERE o.SalesPersonID = @salespersonid AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101') AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101') ); END ; GO Notice the evil words? They’re required. Try to remove them, you just get an error. That’s right – any scalar function is procedural, despite the fact that you wrap up a sub-query inside that RETURN statement. It’s as ugly as anything. Hopefully this will change in future versions. Let’s have a look at how this is reflected in an execution plan. Here’s a query, its Actual plan, and its Estimated plan: SELECT e.LoginID, y.year, dbo.FetchSales_scalar(p.SalesPersonID, y.year) AS NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID; We see here that the cost of the scalar function is about twice that of the outer query. Nicely, the query optimizer has worked out that it doesn’t need the Employee table, but that’s a bit of a red herring here. There’s actually something way more significant going on. If I look at the properties of that UDF operator, it tells me that the Estimated Subtree Cost is 0.337999. If I just run the query SELECT dbo.FetchSales_scalar(281,2003); we see that the UDF cost is still unchanged. You see, this 0.0337999 is the cost of running the scalar function ONCE. But when we ran that query with the CROSS JOIN in it, we returned quite a few rows. 68 in fact. Could’ve been a lot more, if we’d had more salespeople or more years. And so we come to the biggest problem. This procedure (I don’t want to call it a function) is getting called 68 times – each one between twice as expensive as the outer query. And because it’s calling it in a separate context, there is even more overhead that I haven’t considered here. The cheek of it, to say that the Compute Scalar operator here costs 0%! I know a number of IT projects that could’ve used that kind of costing method, but that’s another story that I’m not going to go into here. Let’s look at a better way. Suppose our scalar function had been implemented as an inline one. Then it could have been expanded out like a sub-query. It could’ve run something like this: SELECT e.LoginID, y.year, (SELECT COUNT(*) FROM Sales.SalesOrderHeader AS o LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = o.SalesPersonID WHERE o.SalesPersonID = p.SalesPersonID AND o.OrderDate >= DATEADD(year,y.year-2000,'20000101') AND o.OrderDate < DATEADD(year,y.year-2000+1,'20000101') ) AS NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID; Don’t worry too much about the Scan of the SalesOrderHeader underneath a Nested Loop. If you remember from plenty of other posts on the matter, execution plans don’t push the data through. That Scan only runs once. The Index Spool sucks the data out of it and populates a structure that is used to feed the Stream Aggregate. The Index Spool operator gets called 68 times, but the Scan only once (the Number of Executions property demonstrates this). Here, the Query Optimizer has a full picture of what’s being asked, and can make the appropriate decision about how it accesses the data. It can simplify it down properly. To get this kind of behaviour from a function, we need it to be inline. But without inline scalar functions, we need to make our function be table-valued. Luckily, that’s ok. CREATE FUNCTION dbo.FetchSales_inline2(@salespersonid int, @orderyear int) RETURNS table AS RETURN (SELECT COUNT(*) as NumSales FROM Sales.SalesOrderHeader AS o LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = o.SalesPersonID WHERE o.SalesPersonID = @salespersonid AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101') AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101') ); GO But we can’t use this as a scalar. Instead, we need to use it with the APPLY operator. SELECT e.LoginID, y.year, n.NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID OUTER APPLY dbo.FetchSales_inline2(p.SalesPersonID, y.year) AS n; And now, we get the plan that we want for this query. All we’ve done is tell the function that it’s returning a table instead of a single value, and removed the BEGIN and END statements. We’ve had to name the column being returned, but what we’ve gained is an actual inline simplifiable function. And if we wanted it to return multiple columns, it could do that too. I really consider this function to be superior to the scalar function in every way. It does need to be handled differently in the outer query, but in many ways it’s a more elegant method there too. The function calls can be put amongst the FROM clause, where they can then be used in the WHERE or GROUP BY clauses without fear of calling the function multiple times (another horrible side effect of functions). So please. If you see BEGIN and END in a function, remember it’s not really a function, it’s a procedure. And then fix it. @rob_farley

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Extending NerdDinner: Adding Geolocated Flair

- by Jon Galloway

NerdDinner is a website with the audacious goal of “Organizing the world’s nerds and helping them eat in packs.” Because nerds aren’t likely to socialize with others unless a website tells them to do it. Scott Hanselman showed off a lot of the cool features we’ve added to NerdDinner lately during his popular talk at MIX10, Beyond File | New Company: From Cheesy Sample to Social Platform. Did you miss it? Go ahead and watch it, I’ll wait. One of the features we wanted to add was flair. You know about flair, right? It’s a way to let folks who like your site show it off in their own site. For example, here’s my StackOverflow flair: Great! So how could we add some of this flair stuff to NerdDinner? What do we want to show? If we’re going to encourage our users to give up a bit of their beautiful website to show off a bit of ours, we need to think about what they’ll want to show. For instance, my StackOverflow flair is all about me, not StackOverflow. So how will this apply to NerdDinner? Since NerdDinner is all about organizing local dinners, in order for the flair to be useful it needs to make sense for the person viewing the web page. If someone visits from Egypt visits my blog, they should see information about NerdDinners in Egypt. That’s geolocation – localizing site content based on where the browser’s sitting, and it makes sense for flair as well as entire websites. So we’ll set up a simple little callout that prompts them to host a dinner in their area: Hopefully our flair works and there is a dinner near your viewers, so they’ll see another view which lists upcoming dinners near them: The Geolocation Part Generally website geolocation is done by mapping the requestor’s IP address to a geographic area. It’s not an exact science, but I’ve always found it to be pretty accurate. There are (at least) three ways to handle it: You pay somebody like MaxMind for a database (with regular updates) that sits on your server, and you use their API to do lookups. I used this on a pretty big project a few years ago and it worked well. You use HTML 5 Geolocation API or Google Gears or some other browser based solution. I think those are cool (I use Google Gears a lot), but they’re both in flux right now and I don’t think either has a wide enough of an install base yet to rely on them. You might want to, but I’ve heard you do all kinds of crazy stuff, and sometimes it gets you in trouble. I don’t mean talk out of line, but we all laugh behind your back a bit. But, hey, it’s up to you. It’s your flair or whatever. There are some free webservices out there that will take an IP address and give you location information. Easy, and works for everyone. That’s what we’re doing. I looked at a few different services and settled on IPInfoDB. It’s free, has a great API, and even returns JSON, which is handy for Javascript use. The IP query is pretty simple. We hit a URL like this: http://ipinfodb.com/ip_query.php?ip=74.125.45.100&timezone=false … and we get an XML response back like this… <?xml version="1.0" encoding="UTF-8"?> <Response> <Ip>74.125.45.100</Ip> <Status>OK</Status> <CountryCode>US</CountryCode> <CountryName>United States</CountryName> <RegionCode>06</RegionCode> <RegionName>California</RegionName> <City>Mountain View</City> <ZipPostalCode>94043</ZipPostalCode> <Latitude>37.4192</Latitude> <Longitude>-122.057</Longitude> </Response> So we’ll build some data transfer classes to hold the location information, like this: public class LocationInfo { public string Country { get; set; } public string RegionName { get; set; } public string City { get; set; } public string ZipPostalCode { get; set; } public LatLong Position { get; set; } } public class LatLong { public float Lat { get; set; } public float Long { get; set; } } And now hitting the service is pretty simple: public static LocationInfo HostIpToPlaceName(string ip) { string url = "http://ipinfodb.com/ip_query.php?ip={0}&timezone=false"; url = String.Format(url, ip); var result = XDocument.Load(url); var location = (from x in result.Descendants("Response") select new LocationInfo { City = (string)x.Element("City"), RegionName = (string)x.Element("RegionName"), Country = (string)x.Element("CountryName"), ZipPostalCode = (string)x.Element("CountryName"), Position = new LatLong { Lat = (float)x.Element("Latitude"), Long = (float)x.Element("Longitude") } }).First(); return location; } Getting The User’s IP Okay, but first we need the end user’s IP, and you’d think it would be as simple as reading the value from HttpContext: HttpContext.Current.Request.UserHostAddress But you’d be wrong. Sorry. UserHostAddress just wraps HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"], but that doesn’t get you the IP for users behind a proxy. That’s in another header, “HTTP_X_FORWARDED_FOR". So you can either hit a wrapper and then check a header, or just check two headers. I went for uniformity: string SourceIP = string.IsNullOrEmpty(Request.ServerVariables["HTTP_X_FORWARDED_FOR"]) ? Request.ServerVariables["REMOTE_ADDR"] : Request.ServerVariables["HTTP_X_FORWARDED_FOR"]; We’re almost set to wrap this up, but first let’s talk about our views. Yes, views, because we’ll have two. Selecting the View We wanted to make it easy for people to include the flair in their sites, so we looked around at how other people were doing this. The StackOverflow folks have a pretty good flair system, which allows you to include the flair in your site as either an IFRAME reference or a Javascript include. We’ll do both. We have a ServicesController to handle use of the site information outside of NerdDinner.com, so this fits in pretty well there. We’ll be displaying the same information for both HTML and Javascript flair, so we can use one Flair controller action which will return a different view depending on the requested format. Here’s our general flow for our controller action: Get the user’s IP Translate it to a location Grab the top three upcoming dinners that are near that location Select the view based on the format (defaulted to “html”) Return a FlairViewModel which contains the list of dinners and the location information public ActionResult Flair(string format = "html") { string SourceIP = string.IsNullOrEmpty( Request.ServerVariables["HTTP_X_FORWARDED_FOR"]) ? Request.ServerVariables["REMOTE_ADDR"] : Request.ServerVariables["HTTP_X_FORWARDED_FOR"]; var location = GeolocationService.HostIpToPlaceName(SourceIP); var dinners = dinnerRepository. FindByLocation(location.Position.Lat, location.Position.Long). OrderByDescending(p => p.EventDate).Take(3); // Select the view we'll return. // Using a switch because we'll add in JSON and other formats later. string view; switch (format.ToLower()) { case "javascript": view = "JavascriptFlair"; break; default: view = "Flair"; break; } return View( view, new FlairViewModel { Dinners = dinners.ToList(), LocationName = string.IsNullOrEmpty(location.City) ? "you" : String.Format("{0}, {1}", location.City, location.RegionName) } ); } Note: I’m not in love with the logic here, but it seems like overkill to extract the switch statement away when we’ll probably just have two or three views. What do you think? The HTML View The HTML version of the view is pretty simple – the only thing of any real interest here is the use of an extension method to truncate strings that are would cause the titles to wrap. public static string Truncate(this string s, int maxLength) { if (string.IsNullOrEmpty(s) || maxLength <= 0) return string.Empty; else if (s.Length > maxLength) return s.Substring(0, maxLength) + "..."; else return s; } So here’s how the HTML view ends up looking: <%@ Page Title="" Language="C#" Inherits="System.Web.Mvc.ViewPage<FlairViewModel>" %> <%@ Import Namespace="NerdDinner.Helpers" %> <%@ Import Namespace="NerdDinner.Models" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Nerd Dinner</title> <link href="/Content/Flair.css" rel="stylesheet" type="text/css" /> </head> <body> <div id="nd-wrapper"> <h2 id="nd-header">NerdDinner.com</h2> <div id="nd-outer"> <% if (Model.Dinners.Count == 0) { %> <div id="nd-bummer"> Looks like there's no Nerd Dinners near <%:Model.LocationName %> in the near future. Why not <a target="_blank" href="http://www.nerddinner.com/Dinners/Create">host one</a>?</div> <% } else { %> <h3> Dinners Near You</h3> <ul> <% foreach (var item in Model.Dinners) { %> <li> <%: Html.ActionLink(String.Format("{0} with {1} on {2}", item.Title.Truncate(20), item.HostedBy, item.EventDate.ToShortDateString()), "Details", "Dinners", new { id = item.DinnerID }, new { target = "_blank" })%></li> <% } %> </ul> <% } %> <div id="nd-footer"> More dinners and fun at <a target="_blank" href="http://nrddnr.com">http://nrddnr.com</a></div> </div> </div> </body> </html> You’d include this in a page using an IFRAME, like this: <IFRAME height=230 marginHeight=0 src="http://nerddinner.com/services/flair" frameBorder=0 width=160 marginWidth=0 scrolling=no></IFRAME> The Javascript view The Javascript flair is written so you can include it in a webpage with a simple script include, like this: <script type="text/javascript" src="http://nerddinner.com/services/flair?format=javascript"></script> The goal of this view is very similar to the HTML embed view, with a few exceptions: We’re creating a script element and adding it to the head of the document, which will then document.write out the content. Note that you have to consider if your users will actually have a <head> element in their documents, but for website flair use cases I think that’s a safe bet. Since the content is being added to the existing page rather than shown in an IFRAME, all links need to be absolute. That means we can’t use Html.ActionLink, since it generates relative routes. We need to escape everything since it’s being written out as strings. We need to set the content type to application/x-javascript. The easiest way to do that is to use the <%@ Page ContentType%> directive. <%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage<NerdDinner.Models.FlairViewModel>" ContentType="application/x-javascript" %> <%@ Import Namespace="NerdDinner.Helpers" %> <%@ Import Namespace="NerdDinner.Models" %> document.write('<script>var link = document.createElement(\"link\");link.href = \"http://nerddinner.com/content/Flair.css\";link.rel = \"stylesheet\";link.type = \"text/css\";var head = document.getElementsByTagName(\"head\")[0];head.appendChild(link);</script>'); document.write('<div id=\"nd-wrapper\"><h2 id=\"nd-header\">NerdDinner.com</h2><div id=\"nd-outer\">'); <% if (Model.Dinners.Count == 0) { %> document.write('<div id=\"nd-bummer\">Looks like there\'s no Nerd Dinners near <%:Model.LocationName %> in the near future. Why not <a target=\"_blank\" href=\"http://www.nerddinner.com/Dinners/Create\">host one</a>?</div>'); <% } else { %> document.write('<h3> Dinners Near You</h3><ul>'); <% foreach (var item in Model.Dinners) { %> document.write('<li><a target=\"_blank\" href=\"http://nrddnr.com/<%: item.DinnerID %>\"><%: item.Title.Truncate(20) %> with <%: item.HostedBy %> on <%: item.EventDate.ToShortDateString() %></a></li>'); <% } %> document.write('</ul>'); <% } %> document.write('<div id=\"nd-footer\"> More dinners and fun at <a target=\"_blank\" href=\"http://nrddnr.com\">http://nrddnr.com</a></div></div></div>'); Getting IP’s for Testing There are a variety of online services that will translate a location to an IP, which were handy for testing these out. I found http://www.itouchmap.com/latlong.html to be most useful, but I’m open to suggestions if you know of something better. Next steps I think the next step here is to minimize load – you know, in case people start actually using this flair. There are two places to think about – the NerdDinner.com servers, and the services we’re using for Geolocation. I usually think about caching as a first attack on server load, but that’s less helpful here since every user will have a different IP. Instead, I’d look at taking advantage of Asynchronous Controller Actions, a cool new feature in ASP.NET MVC 2. Async Actions let you call a potentially long-running webservice without tying up a thread on the server while waiting for the response. There’s some good info on that in the MSDN documentation, and Dino Esposito wrote a great article on Asynchronous ASP.NET Pages in the April 2010 issue of MSDN Magazine. But let’s think of the children, shall we? What about ipinfodb.com? Well, they don’t have specific daily limits, but they do throttle you if you put a lot of traffic on them. From their FAQ: We do not have a specific daily limit but queries that are at a rate faster than 2 per second will be put in "queue". If you stay below 2 queries/second everything will be normal. If you go over the limit, you will still get an answer for all queries but they will be slowed down to about 1 per second. This should not affect most users but for high volume websites, you can either use our IP database on your server or we can whitelist your IP for 5$/month (simply use the donate form and leave a comment with your server IP). Good programming practices such as not querying our API for all page views (you can store the data in a cookie or a database) will also help not reaching the limit. So the first step there is to save the geolocalization information in a time-limited cookie, which will allow us to look up the local dinners immediately without having to hit the geolocation service.

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