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• Browsers (IE and Firefox) freeze when copying large amount of text

  - by Matt

  I have a web application - a Java servlet - that delivers data to users in the form of a text printout in a browser (text marked up with HTML in order to display in the browser as we want it to). The text does display in different colors, though most of it is black. One typical mode of operation is this: 1. User submits a form to request data. 2. Servlet delivers HTML file to browser. 3. User does CTRL+A to select all the text. 4. User does CTRL+C to copy all the text. 5. User goes to a text editor and does CTRL+V to paste the text. In the testing where I'm having this problem, step #2 successfully loads all the data - we wait for that to complete. We can scroll down to the end of what the browser loaded and see the end of the data. However, the browser freezes on step #3 (Firefox) or on step #4 (IE). Because step #2 finishes, I think it is a browser/memory issue, and not an issue with the web application. If I run queries to deliver smaller amounts of data (but after several queries we get the same data we would have above in one query) and copy/paste this text, the file I save it into ends up being about 8 MB. If I save the browser's displayed HTML to a file on my computer via File-Save As from the browser menu, it works fine and the file is about 22 MB. We've tried this on 2 different computers at work (both running Windows XP, with at least 2 GB of RAM and many GB of free disk space), using Firefox and IE. We also tried it on a home computer from a home network outside of work (thinking it might be our IT security software causing the problem), running Windows 7 using IE, and still had the problem. When I've done this, I can see whatever browser I'm using utilizing the CPU at 50%. Firefox's memory usage grows to about 1 GB; IE's stays in the several hundred MBs. We once let this run for half an hour, and it did not complete. I'm most likely going to modify the web app to have an option of delivering a plain text file for download, and I imagine that will get the users what they need. But for the mean time, and because I'm curious - and I don't like my application freezing people's browsers, does anyone have any ideas about the browser freezing? I understand that sometimes you just reach your memory limit, but 22 MB sounds to me like an amount I should be able to copy to the clipboard.

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• Suggest an alternative way to organize/build a database solution.

  - by Hamish Grubijan

  We are using Visual Studio 2010, but this was first conceived with VS2003. I will forward the best suggestions to my team. The current setup almost makes me vomit. It is a C# solution with most projects containing .sql files. Because we support Microsoft, Oracle, and Sybase, and so home-brewed a pre-processor, much like C preprocessor, except that substitutions are performed by a home-brewed C# program without using yacc and tools like that. #ifdefs are used for conditional macro definitions, and yeah - macros are the way this is done. A macro can expand to another macro or two, but this should eventually terminate. Only macros have #ifdef in them - the rest of the SQL-like code just uses these macros. Now, the various configurations: Debug, MNDebug, MNRelease, Release, SQL_APPLY_ALL, SQL_APPLY_MSFT, SQL_APPLY_ORACLE, SQL_APPLY_SYBASE, SQL_BUILD_OUTPUT_ALL, SQL_COMPILE, as well as 2 more. Also: Any CPU, Mixed Platforms, Win32. What drives me nuts is having to configure it correctly as well as choosing the right one out of 12 x 3 = 36 configurations as well as having to substitute database name depending on the type of database: config, main, or gateway. I am thinking that configuration should be reduced to just Debug, Release, and SQL_APPLY. Also, using 0, 1, and 2 seems so 80s ... Finally, I think my intention to build or not to build 3 types of databases for 3 types of vendors should be configured with just a tic tac toe board like: XOX OOX XXX In this case it would mean build MSFT+CONFIG, all SYBASE, and all GATEWAY. Still, the overall thing which uses a text file and a pre-processor and many configurations seems incredibly clunky. It is year 2010 now and someone out there is bound to have a very clean and/or creative tool/solution. The only pro would be that the existing collection of macros has been well tested. Have you ever had to write SQL that would work for several vendors? How did you do it? SqlVars.txt (Every one of 30 users makes a copy of a template and modifies this to suit their needs): // This is the default parameters file and should not be changed. // You can overwrite any of these parameters by copying the appropriate // section to override into SqlVars.txt and providing your own information. //Build types are 0-Config, 1-Main, 2-Gateway BUILD_TYPE=1 REMOVE_COMMENTS=1 // Login information used when applying to a Microsoft SQL server database SQL_APPLY_MSFT_version=SQL2005 SQL_APPLY_MSFT_database=msftdb SQL_APPLY_MSFT_server=ABC SQL_APPLY_MSFT_user=msftusr SQL_APPLY_MSFT_password=msftpwd // Login information used when applying to an Oracle database SQL_APPLY_ORACLE_version=ORACLE10g SQL_APPLY_ORACLE_server=oradb SQL_APPLY_ORACLE_user=orausr SQL_APPLY_ORACLE_password=orapwd // Login information used when applying to a Sybase database SQL_APPLY_SYBASE_version=SYBASE125 SQL_APPLY_SYBASE_database=sybdb SQL_APPLY_SYBASE_server=sybdb SQL_APPLY_SYBASE_user=sybusr SQL_APPLY_SYBASE_password=sybpwd ... (THIS GOES ON)

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• Archive tar files to a different location inperl

  - by user314261

  Hi, I am a newbee in Perl. I am reading a directory having some archive files and uncompressing the archive files one by one. Everything seems well however the files are getting uncompressed in the folder which has the main perl code module which is running the sub modules. I want the archive to be generated in the folder I specify. This is my code: sub ExtractFile { #Read the folder which was copied in the output path recursively and extract if any file is compressed my $dirpath = $_[0]; opendir(D, "$dirpath") || die "Can't open dir $dirpath: $!\n"; my @list = readdir(D); closedir(D); foreach my $f (@list) { print " \$f = $f"; if(-f $dirpath."/$f") { #print " File in directory $dirpath \n ";#is \$f = $f\n"; my($file_name, $file_dirname,$filetype)= fileparse($f,qr{\..*}); #print " \nThe file extension is $filetype"; #print " \nThe file name is is $file_name"; # If compressed file then extract the file if($filetype eq ".tar" or $filetype eq ".tzr.gz") { my $arch_file = $dirpath."/$f"; print "\n file to be extracted is $arch_file"; my $tar = Archive::Tar->new($arch_file); #$tar->extract() or die ("Cannot extract file $arch_file"); #mkdir($dirpath."/$file_name"); $tar->extract_file($arch_file,$dirpath."/$file_name" ) or die ("Cannot extract file $arch_file"); } } if(-d $dirpath."/$f") { if($f eq "." or $f eq "..") { next; } print " Directory\n";# is $f"; ExtractFile($dirpath."/$f"); } } } The method ExtractFile is called recursively to loop all the archives. When using $tar-extract() it uncompresses in the folder which calls this metohd. when I use $tar-extract_file($arch_file,$dirpath."/$file_name" ) I get an error : No such file in archive: '/home/fsang/dante/workspace/output/s.tar' at /home/fsang/dante/lib/Extraction.pm line 80 Please help I have checked that path and input output there is no issue with it. Seems some usage problem I am not aware of for $tar-extract_file(). Many thanks for anyone resolving this issue. Regards, Sakshi

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• NVIDIA graphics driver in Ubuntu 12.04

  - by user924501

  So my overall goal is that I want to be able to code with CUDA enabled applications. However, upon many days of searching, using installation walkthroughs, and reinstalling countless times after driver failure... I'm now here as a last resort. I cannot get Ubuntu 12.04 LTS to install the NVIDIA 295.59 driver for my GeForce GT 540M NVIDIA graphics card. My main system specs is as follows... (I believe having the Intel processor may be the problem) DELL Laptop XPS L502X Intel® Core™ i7-2620M CPU @ 2.70GHz × 4 Intel Integrated Graphics 64 bit NVIDIA GeForce GT 540M Ubuntu 12.04 LTS All other specs are irrelevant unless I forgot something? Methods Tried: aptitude install nvidia-current (all packages) Results: Nothing really happened. Nothing in the additional drivers menu appeared, nor was the NVIDIA X Server settings application allowing access because it thought there was no NVIDIA X Server installed. Downloaded driver from nvidia.com. Set nomodeset in the grub boot menu through /boot/grub/grub.cfg Went to console and turned off lightdm. Installed the driver, but it said the pre-install failed? (mean anything?) Started up lightdm again. Results: NVIDIA X Server settings still didn't notice it. Even tried to do nvidia-xconfig multiple times. I also went into the config file to make sure the driver setting said "nvidia". aptitude install nvidia-173 (all packages) Results: Couldn't find the xorg-video-abi-10 virtual package. It was nowhere to be found and the ubuntu forums everywhere had no answers. Lots of people were having this problem. This is easily done in windows, simply download the driver and debug in visual studio with no problems at all. I'd like clear step-by-step instructions on how I should go about this. I'm relatively new to linux but I can find my way around pretty well so you aren't talking to a straight-up beginner. Also, if you think another thread may have the answer please post because I was having a hard time looking for my specific type of problem. TL;DR I want to have access to my GPU so I can code with CUDA while in Ubuntu 12.04 on my 64 bit laptop that also has Intel integrated graphics on the processor. Solution: sudo apt-add-repository ppa:ubuntu-x-swat/x-updates && sudo apt-get update && sudo apt-get upgrade && sudo apt-get install nvidia-current

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• JavaScript - Inheritance in Constructors

  - by j0ker

  For a JavaScript project we want to introduce object inheritance to decrease code duplication. However, I cannot quite get it working the way I want and need some help. We use the module pattern. Suppose there is a super element: a.namespace('a.elements.Element'); a.elements.Element = (function() { // public API -- constructor Element = function(properties) { this.id = properties.id; }; // public API -- prototype Element.prototype = { getID: function() { return this.id; } }; return Element; }()); And an element inheriting from this super element: a.namespace('a.elements.SubElement'); a.elements.SubElement = (function() { // public API -- constructor SubElement = function(properties) { // inheritance happens here // ??? this.color = properties.color; this.bogus = this.id + 1; }; // public API -- prototype SubElement.prototype = { getColor: function() { return this.color; } }; return SubElement; }()); You will notice that I'm not quite sure how to implement the inheritance itself. In the constructor I have to be able to pass the parameter to the super object constructor and create a super element that is then used to create the inherited one. I need a (comfortable) possibility to access the properties of the super object within the constructor of the new object. Ideally I could operate on the super object as if it was part of the new object. I also want to be able to create a new SubElement and call getID() on it. What I want to accomplish seems like the traditional class based inheritance. However, I'd like to do it using prototypal inheritance since that's the JavaScript way. Is that even doable? Thanks in advance! EDIT: Fixed usage of private variables as suggested in the comments. EDIT2: Another change of the code: It's important that id is accessible from the constructor of SubElement.

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• RequestFactoryEditorDriver getting edited data after flush

  - by Deanna

  Let me start with I have a solution, but I don't really think it is elegant. So, I am looking for a cleaner way to do this. I have an EntityProxy displayed in a view panel. The view panel is a RequestFactoryEditorDriver only using display mode. The user clicks on a data element and opens a popup editor to edit a data element of the EntityProxy with a few more bits of data than is displayed in the view panel. When the user saves the element I need the view panel to update the display. I ran into a problem because the RequestFactoryEditorDriver of the popup editor flow doesn't let you get to the edited data. The driver uses the passed in context and sends it to the server. The context returned out of flush only allows a Receiver even if you cast it to the type of context you stored in the editor driver in the edit() call. It doesn't appear to send and EntityProxyChanged event either, so I couldn't listen for that and update the display view. The solution I found was to change my domain object persist to return the newly saved entity. Then create the popup editor like this editor.getSaveButtonClickHandler().addClickHandler(createSaveHandler(driver, editor)); // initialize the Driver and edit the given text. driver.initialize(rf, editor); PlayerProfileCtx ctx = rf.playerProfile(); ctx.persist().using(playerProfile).with(driver.getPaths()) .to(new Receiver<PlayerProfileProxy>(){ @Override public void onSuccess(PlayerProfileProxy profile) { editor.hide(); playerProfile = profile; viewDriver.display(playerProfile); } }); driver.edit(playerProfile, ctx); editor.centerAndShow(); Then in the save handler I just fire the context I get from the flush. While this approach works, it doesn't seem right. It would seem I should subscribe to the entitychanged event in the display view and update the entity and the view from there. Also this approach saves the complete entity, not just the changed bits, which will increase bandwidth usage. What I would think should happen, is when you flush the entity it should 'optimistically' update the rf managed version of the entity and fire the entity proxy changed event. Only reverting the entity if something went wrong in the save. The actual save should only send the changed bits. In this way there isn't a need to refetch the whole entity and send that complete data over the wire twice. Is there a better solution?

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• No more memory available in Mathematica, Fit the parameters of system of differential equation

  - by user1058051

  I encountered a memory problem in Mathematica, when I tried to process my experimental data. It's a system of two differential equations and I need to find most suitable parameters. Unfortunately I am not a Pro in Mathematica, so the program used a lot of memory, when the parameter epsilon is more than 0.4. When it less than 0.4, the program work properly. The command 'historylength = 0' and attempts to reduce the Accuracy Goal and WorkingPrecision didn`t help. I can't use ' clear Cache ', because there isnt a circle. I'm trying to understand what mistakes I made, and how I may limit the memory usage. I have already bought extra-RAM, now its 4GB, and now I haven't free memory-slots in motherboard Remove["Global`*"]; T=13200; L = 0.085; e = 0.41; v = 0.000557197; q = 0.1618; C0 = 0.0256; R = 0.00075; data = {{L,600,0.141124587},{L,1200,0.254134509},{L,1800,0.342888644}, {L,2400,0.424476295},{L,3600,0.562844542},{L,4800,0.657111356}, {L,6000,0.75137817},{L,7200,0.815876516},{L,8430,0.879823594}, {L,9000,0.900771775},{L,13200,1}}; model[(De_)?NumberQ, (Kf_)?NumberQ, (Y_)?NumberQ] := model[De, Kf, Y] = yeld /.Last[Last[ NDSolve[{ v (Ci^(1,0))[z,t]+(Ci^(0,1))[z,t]== -((3 (1-e) Kf (Ci[z,t]-C0))/ (R e (1-(R Kf (1-R/r[z,t]))/De))), (r^(0,1))[z,t]== (R^2 Kf (Ci[z,t]-C0))/ (q r[z,t]^2 (1-(R Kf (1-R/r[z,t]))/De)), (yeld^(0,1))[z,t]== Y*(v e Ci[z,t])/(L q (1-e)), r[z,0]==R, Ci[z,0]==0, Ci[0,t]==0, yeld[z,0]==0}, {r[z,t],Ci[z,t],yeld},{z,0,L},{t,0,T}]]] fit = FindFit[data, {model[De, Kf, Y][z, t], {Y > 0.97, Y < 1.03, Kf > 10^-6, Kf < 10^-4, De > 10^-13, De < 10^-9}}, {{De,7*10^-13}, {Kf, 10^-5}, {Y, 1}}, {z, t}, Method -> NMinimize] data = {{600,0.141124587},{1200,0.254134509},{1800,0.342888644}, {2400,0.424476295},{3600,0.562844542},{4800,0.657111356}, {6000,0.75137817},{7200,0.815876516},{8430,0.879823594}, {9000,0.900771775},{13200,1}}; YYY = model[ De /. fit[[1]], Kf /. fit[[2]], Y /. fit[[3]]]; Show[Plot[Evaluate[YYY[L,t]],{t,0,T},PlotRange->All], ListPlot[data,PlotStyle->Directive[PointSize[Medium],Red]]] the link on the .nb file http://www.4shared.com/folder/249TSjlz/_online.html

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• Why is Dictionary.First() so slow?

  - by Rotsor

  Not a real question because I already found out the answer, but still interesting thing. I always thought that hash table is the fastest associative container if you hash properly. However, the following code is terribly slow. It executes only about 1 million iterations and takes more than 2 minutes of time on a Core 2 CPU. The code does the following: it maintains the collection todo of items it needs to process. At each iteration it takes an item from this collection (doesn't matter which item), deletes it, processes it if it wasn't processed (possibly adding more items to process), and repeats this until there are no items to process. The culprit seems to be the Dictionary.Keys.First() operation. The question is why is it slow? Stopwatch watch = new Stopwatch(); watch.Start(); HashSet<int> processed = new HashSet<int>(); Dictionary<int, int> todo = new Dictionary<int, int>(); todo.Add(1, 1); int iterations = 0; int limit = 500000; while (todo.Count > 0) { iterations++; var key = todo.Keys.First(); var value = todo[key]; todo.Remove(key); if (!processed.Contains(key)) { processed.Add(key); // process item here if (key < limit) { todo[key + 13] = value + 1; todo[key + 7] = value + 1; } // doesn't matter much how } } Console.WriteLine("Iterations: {0}; Time: {1}.", iterations, watch.Elapsed); This results in: Iterations: 923007; Time: 00:02:09.8414388. Simply changing Dictionary to SortedDictionary yields: Iterations: 499976; Time: 00:00:00.4451514. 300 times faster while having only 2 times less iterations. The same happens in java. Used HashMap instead of Dictionary and keySet().iterator().next() instead of Keys.First().

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• Using a large list of terms, search through page text and replace words with links

  - by dunc

  A while ago I posted this question asking if it's possible to convert text to HTML links if they match a list of terms from my database. I have a fairly huge list of terms - around 6000. The accepted answer on that question was superb, but having never used XPath, I was at a loss when problems started occurring. At one point, after fiddling with code, I somehow managed to add over 40,000 random characters to our database - the majority of which required manual removal. Since then I've lost faith in that idea and the more simple PHP solutions simply weren't efficient enough to deal with the amount of data and the quantity of terms. My next attempt at a solution is to write a JS script which, once the page has loaded, retrieves the terms and matches them against the text on a page. This answer has an idea which I'd like to attempt. I would use AJAX to retrieve the terms from the database, to build an object such as this: var words = [ { word: 'Something', link: 'http://www.something.com' }, { word: 'Something Else', link: 'http://www.something.com/else' } ]; When the object has been built, I'd use this kind of code: //for each array element $.each(words, function() { //store it ("this" is gonna become the dom element in the next function) var search = this; $('.message').each( function() { //if it's exactly the same if ($(this).text() === search.word) { //do your magic tricks $(this).html('<a href="' + search.link + '">' + search.link + '</a>'); } } ); } ); Now, at first sight, there is a major issue here: with 6,000 terms, will this code be in any way efficient enough to do what I'm trying to do?. One option would possibly be to perform some of the overhead within the PHP script that the AJAX communicates with. For instance, I could send the ID of the post and then the PHP script could use SQL statements to retrieve all of the information from the post and match it against all 6,000 terms.. then the return call to the JavaScript could simply be the matching terms, which would significantly reduce the number of matches the above jQuery would make (around 50 at most). I have no problem with the script taking a few seconds to "load" on the user's browser, as long as it isn't impacting their CPU usage or anything like that. So, two questions in one: Can I make this work? What steps can I take to make it as efficient as possible? Thanks in advance,

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• Optimizing GDI+ drawing?

  - by user146780

  I'm using C++ and GDI+ I'm going to be making a vector drawing application and want to use GDI+ for the drawing. I'v created a simple test to get familiar with it: case WM_PAINT: GetCursorPos(&mouse); GetClientRect(hWnd,&rct); hdc = BeginPaint(hWnd, &ps); MemDC = CreateCompatibleDC(hdc); bmp = CreateCompatibleBitmap(hdc, 600, 600); SelectObject(MemDC,bmp); g = new Graphics(MemDC); for(int i = 0; i < 1; ++i) { SolidBrush sb(Color(255,255,255)); g->FillRectangle(&sb,rct.top,rct.left,rct.right,rct.bottom); } for(int i = 0; i < 250; ++i) { pts[0].X = 0; pts[0].Y = 0; pts[1].X = 10 + mouse.x * i; pts[1].Y = 0 + mouse.y * i; pts[2].X = 10 * i + mouse.x; pts[2].Y = 10 + mouse.y * i; pts[3].X = 0 + mouse.x; pts[3].Y = (rand() % 600) + mouse.y; Point p1, p2; p1.X = 0; p1.Y = 0; p2.X = 300; p2.Y = 300; g->FillPolygon(&b,pts,4); } BitBlt(hdc,0,0,900,900,MemDC,0,0,SRCCOPY); EndPaint(hWnd, &ps); DeleteObject(bmp); g->ReleaseHDC(MemDC); DeleteDC(MemDC); delete g; break; I'm wondering if I'm doing it right, or if I have areas killing the cpu. Because right now it takes ~ 1sec to render this and I want to be able to have it redraw itself very quickly. Thanks In a real situation would it be better just to figure out the portion of the screen to redraw and only redraw the elements withing bounds of this?

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• Android: How to properly exit application when inconsistent condition is unavoidable?

  - by Bevor

  First of all I already read about all this discussion that it isn't a good idea to manually exit an Android application. But in my case it seems to be needed. I have an AsyncTask which does a lof of operations in background. That means downloading data, saving it to local storage and preparing it for usage in application. It could happen that there is no internet connection or something different happens. For all that cases I have an Exception handling which returns the result. And if there is an exception, the application is unusable so I need to exit it. My question is, do I have to do some unregistration unloading or unbinding tasks or something when I exit the application by code or is System.exit(0) ok? I do all this in an AsyncTask, see my example: public class InitializationTask extends AsyncTask<Void, Void, InitializationResult> { private ProcessController processController = new ProcessController(); private ProgressDialog progressDialog; private Activity mainActivity; public InitializationTask(Activity mainActivity) { this.mainActivity = mainActivity; } @Override protected void onPreExecute() { super.onPreExecute(); progressDialog = new ProgressDialog(mainActivity); progressDialog.setMessage("Die Daten werden aufbereitet.\nBitte warten..."); progressDialog.setIndeterminate(true); //means that the "loading amount" is not measured. progressDialog.setCancelable(false); progressDialog.show(); }; @Override protected InitializationResult doInBackground(Void... params) { return processController.initializeData(); } @Override protected void onPostExecute(InitializationResult result) { super.onPostExecute(result); progressDialog.dismiss(); if (!result.isValid()) { AlertDialog.Builder dialog = new AlertDialog.Builder(mainActivity); dialog.setTitle("Initialisierungsfehler"); dialog.setMessage(result.getReason()); dialog.setPositiveButton("Ok", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { dialog.cancel(); //TODO cancel application System.exit(0); } }); dialog.show(); } } }

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• Should the argument be passed by reference in this .net example?

  - by Hamish Grubijan

  I have used Java, C++, .Net. (in that order). When asked about by-value vs. by-ref on interviews, I have always done well on that question ... perhaps because nobody went in-depth on it. Now I know that I do not see the whole picture. I was looking at this section of code written by someone else: XmlDocument doc = new XmlDocument(); AppendX(doc); // Real name of the function is different AppendY(doc); // ditto When I saw this code, I thought: wait a minute, should not I use a ref in front of doc variable (and modify AppendX/Y accordingly? it works as written, but made me question whether I actually understand the ref keyword in C#. As I thought about this more, I recalled early Java days (college intro language). A friend of mine looked at some code I have written and he had a mental block - he kept asking me which things are passed in by reference and when by value. My ignorant response was something like: Dude, there is only one kind of arg passing in Java and I forgot which one it is :). Chill, do not over-think and just code. Java still does not have a ref does it? Yet, Java hackers seem to be productive. Anyhow, coding in C++ exposed me to this whole by reference business, and now I am confused. Should ref be used in the example above? I am guessing that when ref is applied to value types: primitives, enums, structures (is there anything else in this list?) it makes a big difference. And ... when applied to objects it does not because it is all by reference. If things were so simple, then why would not the compiler restrict the usage of ref keyword to a subset of types. When it comes to objects, does ref serve as a comment sort of? Well, I do remember that there can be problems with null and ref is also useful for initializing multiple elements within a method (since you cannot return multiple things with the same easy as you would do in Python). Thanks.

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• AudioTrack lag: obtainBuffer timed out

  - by BTR

  I'm playing WAVs on my Android phone by loading the file and feeding the bytes into AudioTrack.write() via the FileInputStream BufferedInputStream DataInputStream method. The audio plays fine and when it is, I can easily adjust sample rate, volume, etc on the fly with nice performance. However, it's taking about two full seconds for a track to start playing. I know AudioTrack has an inescapable delay, but this is ridiculous. Every time I play a track, I get this: 03-13 14:55:57.100: WARN/AudioTrack(3454): obtainBuffer timed out (is the CPU pegged?) 0x2e9348 user=00000960, server=00000000 03-13 14:55:57.340: WARN/AudioFlinger(72): write blocked for 233 msecs, 9 delayed writes, thread 0xba28 I've noticed that the delayed write count increases by one every time I play a track -- even across multiple sessions -- from the time the phone has been turned on. The block time is always 230 - 240ms, which makes sense considering a minimum buffer size of 9600 on this device (9600 / 44100). I've seen this message in countless searches on the Internet, but it usually seems to be related to not playing audio at all or skipping audio. In my case, it's just a delayed start. I'm running all my code in a high priority thread. Here's a truncated-yet-functional version of what I'm doing. This is the thread callback in my playback class. Again, this works (only playing 16-bit, 44.1kHz, stereo files right now), it just takes forever to start and has that obtainBuffer/delayed write message every time. public void run() { // Load file FileInputStream mFileInputStream; try { // mFile is instance of custom file class -- this is correct, // so don't sweat this line mFileInputStream = new FileInputStream(mFile.path()); } catch (FileNotFoundException e) {} BufferedInputStream mBufferedInputStream = new BufferedInputStream(mFileInputStream, mBufferLength); DataInputStream mDataInputStream = new DataInputStream(mBufferedInputStream); // Skip header try { if (mDataInputStream.available() > 44) mDataInputStream.skipBytes(44); } catch (IOException e) {} // Initialize device mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, ConfigManager.SAMPLE_RATE, AudioFormat.CHANNEL_CONFIGURATION_STEREO, AudioFormat.ENCODING_PCM_16BIT, ConfigManager.AUDIO_BUFFER_LENGTH, AudioTrack.MODE_STREAM); mAudioTrack.play(); // Initialize buffer byte[] mByteArray = new byte[mBufferLength]; int mBytesToWrite = 0; int mBytesWritten = 0; // Loop to keep thread running while (mRun) { // This flag is turned on when the user presses "play" while (mPlaying) { try { // Check if data is available if (mDataInputStream.available() > 0) { // Read data from file and write to audio device mBytesToWrite = mDataInputStream.read(mByteArray, 0, mBufferLength); mBytesWritten += mAudioTrack.write(mByteArray, 0, mBytesToWrite); } } catch (IOException e) { } } } } If I can get past the artificially long lag, I can easily deal with the inherit latency by starting my write at a later, predictable position (ie, skip past the minimum buffer length when I start playing a file).

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• VS 2010 IDE 2GB limt

  - by user561732

  I am using VS 2010 on a win 7 64 bit system with 8 GB of memory. My application is 32 bit. While in the VS 2010 .Net IDE, the app shows up in the Windows task manager as "MyApp.vshost.exe *32" while the VS IDE itself shows up as "devenv.exe *32". I checked and it appears that the VS 2010 IDE file (devenv.exe) is complied with the /LargeAddressAware flag. However, when debugging large models, the IDE fails with an Out of memory exception. In the Windows Task manager, the "MyApp.vshost.exe *32" process indicates about 1400 MB of memory usage (while the "devenv.exe *32" process is well under 500 MB). Is it possible to set the "MyApp.vshost.exe *32" process to be /LargeAddressAware in order to avoid this out of memory situation? If so, how can this be done in the IDE. While setting the final application binary to be /LargeAddressAware would work, I still need to be able to debug the app in the IDE with these type of large models. I should also note that my app has a deep object hierarchy with many collections that together required a lot of memory. However, my issue is not related to trying to create say 1 large array that requires greater then 2 GB of memory etc. I should note that I am able to run the same app in the VB6 IDE and not get an out of memory situation as long as the VB6 IDE is made /LargeAddressAware. In the case of VB6, the IDE and the app being debugged are part of the same process (and not split into 2 as is the case with VS 2010.) The VB6 process can be larger then 3 GB without running into out of memory issues. Ultimately, my objective is to have my app run completely in 64 bit to access more memory. I am hoping that in such cases, the IDE will allow the debugging process to exceed 2 GB without crashing (and certainly more then 1.4 GB as is the current case). However, for now, while 95% of my app is 64 bit, I am calling a legacy COM 32 bit DLL and as such, my entire app is forced to still run in 32 bit mode until I replace that DLL.

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• How to remove .zip file in c on windows? (error: Directory not empty)

  - by ExtremeBlue

  include include include include "win32-dirent.h" include include include define MAXFILEPATH 1024 bool IsDirectory(char* path) { WIN32_FIND_DATA w32fd; HANDLE hFindFile; hFindFile = FindFirstFile((PTCHAR)path, &w32fd); if(hFindFile == INVALID_HANDLE_VALUE) { return false; } return w32fd.dwFileAttributes & (FILE_ATTRIBUTE_DIRECTORY); } int RD(const char* folderName) { DIR *dir; struct dirent *ent; dir = opendir(folderName); if(dir != NULL) { while((ent = readdir(dir)) != NULL) { if(strcmp(ent->d_name , ".") == 0 || strcmp(ent->d_name, "..") == 0) { continue; } char fileName[MAXFILEPATH]; sprintf(fileName,"%s%c%s", folderName, '\\', ent->d_name); if(IsDirectory(fileName)) { RD(fileName); } else { unlink(fileName); } } closedir(dir); //chmod(folderName, S_IWRITE | S_IREAD); if(_rmdir(folderName) != 0)perror(folderName); } else { printf("%s <%s>\n","Could Not Open Directory.", folderName); return -1; } return 0; } int main(int argc, char* argv[]) { if(argc < 2) { printf("usage: ./a.out \n"); return 1; } //RD(argv[1]); //_mkdir("12"); //_mkdir("12\\34"); //_rmdir("12\\34"); //_rmdir("12"); char buf[0xff]; sprintf(buf, "unzip -x -q -d 1234 1234.zip"); system(buf); RD("1234"); //unlink("D:\\dev\\c\\project\\removeFolder\\Debug\\1234\\56\\5.txt"); //unlink("D:\\dev\\c\\project\\removeFolder\\Debug\\1234\\56\\6.txt"); //unlink("D:\\dev\\c\\project\\removeFolder\\Debug\\1234\\1_23.zip"); //unlink("D:\\dev\\c\\project\\removeFolder\\Debug\\1234\\4.txt"); //_rmdir("D:\\dev\\c\\project\\removeFolder\\Debug\\1234\\56"); //_rmdir("D:\\dev\\c\\project\\removeFolder\\Debug\\1234"); return 0; } Archive: 1234.zip inflating: 1234/4.txt inflating: 1234/56/5.txt inflating: 1234/56/6.txt inflating: 1234/1_23.zip

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• Styling related issue in IE8

  - by Ajith

  I am using a background image to display as a button. The button shows up well in all versions of firefox, chrome, opera etc. However, the image fails to render itself in IE8. Only the image is not being shown, some of the other class styling gets applied such as width, height etc. Even more confounding is that in another page(though a different class and style sheet), an image of similar proportions gets displayed in similar usage. The image format is JPG. I'm copy-pasting the valid style attributes for both cases as shown by firebug below. None of the below buttons are displayed. button classes are applied as class="cart-button login", class="cart-button update", class="cart-button checkout" and class="cart-button continue" and are inside some divs. .cart-button{ height: 28px; cursor: pointer; border: none; float: left; } .cart-button:hover{ background-position: 0 -28px; } .login{ width: 58px; background:url(/../../templates/animalcare/i/login.jpg)no-repeat; margin:0 0 20px 0; clear: both; } .update{ width: 63px; background:url(/../../templates/animalcare/i/update.jpg)no-repeat; margin:0 0 20px 15px; float: left; } .checkout{ width: 77px; background:url(/../../templates/animalcare/i/checkout.jpg)no-repeat; float:right; margin:0 25px 30px 10px; } .continue{ width: 132px; background:url(/../../templates/animalcare/i/continue.jpg)no-repeat; float:right; margin:0 0 30px 0px; } The below is the only image button that gets displayed. It is located inside a table. It is in a different style sheet - hence the path difference. .add-to-cart{ width:102px; height:28px; float:left; background:url(i/add_to_cart.jpg) no-repeat; cursor:pointer; border:none; margin:10px 0 5px 0; } .add-to-cart:hover{ background-position:0 -28px; }

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• CUDA memory transfer issue

  - by Vaibhav Sundriyal

  I am trying to execute a code which first transfers data from CPU to GPU memory and vice-versa. In spite of increasing the volume of data, the data transfer time remains the same as if no data transfer is actually taking place. I am posting the code. #include <stdio.h> /* Core input/output operations */ #include <stdlib.h> /* Conversions, random numbers, memory allocation, etc. */ #include <math.h> /* Common mathematical functions */ #include <time.h> /* Converting between various date/time formats */ #include <cuda.h> /* CUDA related stuff */ #include <sys/time.h> __global__ void device_volume(float *x_d,float *y_d) { int index = blockIdx.x * blockDim.x + threadIdx.x; } int main(void) { float *x_h,*y_h,*x_d,*y_d,*z_h,*z_d; long long size=9999999; long long nbytes=size*sizeof(float); timeval t1,t2; double et; x_h=(float*)malloc(nbytes); y_h=(float*)malloc(nbytes); z_h=(float*)malloc(nbytes); cudaMalloc((void **)&x_d,size*sizeof(float)); cudaMalloc((void **)&y_d,size*sizeof(float)); cudaMalloc((void **)&z_d,size*sizeof(float)); gettimeofday(&t1,NULL); cudaMemcpy(x_d, x_h, nbytes, cudaMemcpyHostToDevice); cudaMemcpy(y_d, y_h, nbytes, cudaMemcpyHostToDevice); cudaMemcpy(z_d, z_h, nbytes, cudaMemcpyHostToDevice); gettimeofday(&t2,NULL); et = (t2.tv_sec - t1.tv_sec) * 1000.0; // sec to ms et += (t2.tv_usec - t1.tv_usec) / 1000.0; // us to ms printf("\n %ld\t\t%f\t\t",nbytes,et); et=0.0; //printf("%f %d\n",seconds,CLOCKS_PER_SEC); // launch a kernel with a single thread to greet from the device //device_volume<<<1,1>>>(x_d,y_d); gettimeofday(&t1,NULL); cudaMemcpy(x_h, x_d, nbytes, cudaMemcpyDeviceToHost); cudaMemcpy(y_h, y_d, nbytes, cudaMemcpyDeviceToHost); cudaMemcpy(z_h, z_d, nbytes, cudaMemcpyDeviceToHost); gettimeofday(&t2,NULL); et = (t2.tv_sec - t1.tv_sec) * 1000.0; // sec to ms et += (t2.tv_usec - t1.tv_usec) / 1000.0; // us to ms printf("%f\n",et); cudaFree(x_d); cudaFree(y_d); cudaFree(z_d); return 0; } Can anybody help me with this issue? Thanks

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• TFS 2010 Build Custom Activity for Merging Assemblies

  - by Jakob Ehn

  *** The sample build process template discussed in this post is available for download from here: http://cid-ee034c9f620cd58d.office.live.com/self.aspx/BlogSamples/ILMerge.xaml ***   In my previous post I talked about library builds that we use to build and replicate dependencies between applications in TFS. This is typically used for common libraries and tools that several other application need to reference. When the libraries grow in size over time, so does the number of assemblies. So all solutions that uses the common library must reference all the necessary assemblies that they need, and if we for example do a refactoring and extract some code into a new assembly, all the clients must update their references to reflect these changes, otherwise it won’t compile. To improve on this, we use a tool from Microsoft Research called ILMerge (Download from here). It can be used to merge several assemblies into one assembly that contains all types. If you haven’t used this tool before, you should check it out. Previously I have implemented this in builds using a simple batch file that contains the full command, something like this: "%ProgramFiles(x86)%\microsoft\ilmerge\ilmerge.exe" /target:library /attr:ClassLibrary1.bl.dll /out:MyNewLibrary.dll ClassLibrary1.dll ClassLibrar2.dll ClassLibrary3.dll This merges 3 assemblies (ClassLibrary1, 2 and 3) into a new assembly called MyNewLibrary.dll. It will copy the attributes (file version, product version etc..) from ClassLibrary1.dll, using the /attr switch. For more info on ILMerge command line tool, see the above link. This approach works, but requires a little bit too much knowledge for the developers creating builds, therefor I have implemented a custom activity that wraps the use of ILMerge. This makes it much simpler to setup a new build definition and have the build automatically do the merging. The usage of the activity is then implemented as part of the Library Build process template mentioned in the previous post. For this article I have just created a simple build process template that only performs the ILMerge operation.   Below is the code for the custom activity. To make it compile, you need to reference the ILMerge.exe assembly. /// <summary> /// Activity for merging a list of assembies into one, using ILMerge /// </summary> public sealed class ILMergeActivity : BaseCodeActivity { /// <summary> /// A list of file paths to the assemblies that should be merged /// </summary> [RequiredArgument] public InArgument<IEnumerable<string>> InputAssemblies { get; set; } /// <summary> /// Full path to the generated assembly /// </summary> [RequiredArgument] public InArgument<string> OutputFile { get; set; } /// <summary> /// Which input assembly that the attibutes for the generated assembly should be copied from. /// Optional. If not specified, the first input assembly will be used /// </summary> public InArgument<string> AttributeFile { get; set; } /// <summary> /// Kind of assembly to generate, dll or exe /// </summary> public InArgument<TargetKindEnum> TargetKind { get; set; } // If your activity returns a value, derive from CodeActivity<TResult> // and return the value from the Execute method. protected override void Execute(CodeActivityContext context) { string message = InputAssemblies.Get(context).Aggregate("", (current, assembly) => current + (assembly + " ")); TrackMessage(context, "Merging " + message + " into " + OutputFile.Get(context)); ILMerge m = new ILMerge(); m.SetInputAssemblies(InputAssemblies.Get(context).ToArray()); m.TargetKind = TargetKind.Get(context) == TargetKindEnum.Dll ? ILMerge.Kind.Dll : ILMerge.Kind.Exe; m.OutputFile = OutputFile.Get(context); m.AttributeFile = !String.IsNullOrEmpty(AttributeFile.Get(context)) ? AttributeFile.Get(context) : InputAssemblies.Get(context).First(); m.SetTargetPlatform(RuntimeEnvironment.GetSystemVersion().Substring(0,2), RuntimeEnvironment.GetRuntimeDirectory()); m.Merge(); TrackMessage(context, "Generated " + m.OutputFile); } } [Browsable(true)] public enum TargetKindEnum { Dll, Exe } NB: The activity inherits from a BaseCodeActivity class which is an internal helper class which contains some methods and properties useful for moste custom activities. In this case, it uses the TrackeMessage method for writing to the build log. You either need to remove the TrackMessage method calls, or implement this yourself (which is not very hard… ) The custom activity has the following input arguments: InputAssemblies A list with the (full) paths to the assemblies to merge OutputFile The name of the resulting merged assembly AttributeFile Which assembly to use as the template for the attribute of the merged assembly. This argument is optional and if left blank, the first assembly in the input list is used TargetKind Decides what type of assembly to create, can be either a dll or an exe Of course, there are more switches to the ILMerge.exe, and these can be exposed as input arguments as well if you need it. To show how the custom activity can be used, I have attached a build process template (see link at the top of this post) that merges the output of the projects being built (CommonLibrary.dll and CommonLibrary2.dll) into a merged assembly (NewLibrary.dll). The build process template has the following custom process parameters:   The Assemblies To Merge argument is passed into a FindMatchingFiles activity to located all assemblies that are located in the BinariesDirectory folder after the compilation has been performed by Team Build. Here is the complete sequence of activities that performs the merge operation. It is located at the end of the Try, Compile, Test and Associate… sequence: It splits the AssembliesToMerge parameter and appends the full path (using the BinariesDirectory variable) and then enumerates the matching files using the FindMatchingFiles activity. When running the build, you can see that it merges two assemblies into a new one:     And the merged assembly (and associated pdb file) is copied to the drop location together with the rest of the assemblies:

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• ActiveX component can't create Object Error? Check 64 bit Status

  - by Rick Strahl

  If you're running on IIS 7 and a 64 bit operating system you might run into the following error using ASP classic or ASP.NET with COM interop. In classic ASP applications the error will show up as: ActiveX component can't create object   (Error 429) (actually without error handling the error just shows up as 500 error page) In my case the code that's been giving me problems has been a FoxPro COM object I'd been using to serve banner ads to some of my pages. The code basically looks up banners from a database table and displays them at random. The ASP classic code that uses it looks like this: <% Set banner = Server.CreateObject("wwBanner.aspBanner") banner.BannerFile = "wwsitebanners" Response.Write(banner.GetBanner(-1)) %> Originally this code had no specific error checking as above so the ASP pages just failed with 500 error pages from the Web server. To find out what the problem is this code is more useful at least for debugging: <% ON ERROR RESUME NEXT Set banner = Server.CreateObject("wwBanner.aspBanner") Response.Write(err.Number & " - " & err.Description) banner.BannerFile = "wwsitebanners" Response.Write(banner.GetBanner(-1)) %> which results in: 429 - ActiveX component can't create object which at least gives you a slight clue. In ASP.NET invoking the same COM object with code like this: <% dynamic banner = wwUtils.CreateComInstance("wwBanner.aspBanner") as dynamic; banner.cBANNERFILE = "wwsitebanners"; Response.Write(banner.getBanner(-1)); %> results in: Retrieving the COM class factory for component with CLSID {B5DCBB81-D5F5-11D2-B85E-00600889F23B} failed due to the following error: 80040154 Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG)). The class is in fact registered though and the COM server loads fine from a command prompt or other COM client. This error can be caused by a COM server that doesn't load. It looks like a COM registration error. There are a number of traditional reasons why this error can crop up of course. The server isn't registered (run regserver32 to register a DLL server or /regserver on an EXE server) Access permissions aren't set on the COM server (Web account has to be able to read the DLL ie. Network service) The COM server fails to load during initialization ie. failing during startup One thing I always do to check for COM errors fire up the server in a COM client outside of IIS and ensure that it works there first - it's almost always easier to debug a server outside of the Web environment. In my case I tried the server in Visual FoxPro on the server with: loBanners = CREATEOBJECT("wwBanner.aspBanner") loBanners.cBannerFile = "wwsitebanners" ? loBanners.GetBanner(-1) and it worked just fine. If you don't have a full dev environment on the server you can also use VBScript do the same thing and run the .vbs file from the command prompt: Set banner = Server.CreateObject("wwBanner.aspBanner") banner.BannerFile = "wwsitebanners" MsgBox(banner.getBanner(-1)) Since this both works it tells me the server is registered and working properly. This leaves startup failures or permissions as the problem. I double checked permissions for the Application Pool and the permissions of the folder where the DLL lives and both are properly set to allow access by the Application Pool impersonated user. Just to be sure I assigned an Admin user to the Application Pool but still no go. So now what? 64 bit Servers Ahoy A couple of weeks back I had set up a few of my Application pools to 64 bit mode. My server is Server 2008 64 bit and by default Application Pools run 64 bit. Originally when I installed the server I set up most of my Application Pools to 32 bit mainly for backwards compatibility. But as more of my code migrates to 64 bit OS's I figured it'd be a good idea to see how well code runs under 64 bit code. The transition has been mostly painless. Until today when I noticed the problem with the code above when scrolling to my IIS logs and noticing a lot of 500 errors on many of my ASP classic pages. The code in question in most of these pages deals with this single simple COM object. It took a while to figure out that the problem is caused by the Application Pool running in 64 bit mode. The issue is that 32 bit COM objects (ie. my old Visual FoxPro COM component) cannot be loaded in a 64 bit Application Pool. The ASP pages using this COM component broke on the day I switched my main Application Pool into 64 bit mode but I didn't find the problem until I searched my logs for errors by pure chance. To fix this is easy enough once you know what the problem is by switching the Application Pool to Enable 32-bit Applications: Once this is done the COM objects started working correctly again. 64 bit ASP and ASP.NET with DCOM Servers This is kind of off topic, but incidentally it's possible to load 32 bit DCOM (out of process) servers from ASP.NET and ASP classic even if those applications run in 64 bit application pools. In fact, in West Wind Web Connection I use this capability to run a 64 bit ASP.NET handler that talks to a 32 bit FoxPro COM server which allows West Wind Web Connection to run in native 64 bit mode without custom configuration (which is actually quite useful). It's probably not a common usage scenario but it's good to know that you can actually access 32 bit COM objects this way from ASP.NET. For West Wind Web Connection this works out well as the DCOM interface only makes one non-chatty call to the backend server that handles all the rest of the request processing. Application Pool Isolation is your Friend For me the recent incident of failure in the classic ASP pages has just been another reminder to be very careful with moving applications to 64 bit operation. There are many little traps when switching to 64 bit that are very difficult to track and test for. I described one issue I had a couple of months ago where one of the default ASP.NET filters was loading the wrong version (32bit instead of 64bit) which was extremely difficult to track down and was caused by a very sneaky configuration switch error (basically 3 different entries for the same ISAPI filter all with different bitness settings). It took me almost a full day to track this down). Recently I've been taken to isolate individual applications into separate Application Pools rather than my past practice of combining many apps into shared AppPools. This is a good practice assuming you have enough memory to make this work. Application Pool isolate provides more modularity and allows me to selectively move applications to 64 bit. The error above came about precisely because I moved one of my most populous app pools to 64 bit and forgot about the minimal COM object use in some of my old pages. It's easy to forget. To 64bit or Not Is it worth it to move to 64 bit? Currently I'd say -not really. In my - admittedly limited - testing I don't see any significant performance increases. In fact 64 bit apps just seem to consume considerably more memory (30-50% more in my pools on average) and performance is minimally improved (less than 5% at the very best) in the load testing I've performed on a couple of sites in both modes. The only real incentive for 64 bit would be applications that require huge data spaces that exceed the 32 bit 4 gigabyte memory limit. However I have a hard time imagining an application that needs 4 gigs of memory in a single Application Pool :-). Curious to hear other opinions on benefits of 64 bit operation. © Rick Strahl, West Wind Technologies, 2005-2011Posted in COM   ASP.NET  FoxPro  

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• Mulit-tenant ASP.NET MVC – Controllers

  - by zowens

  Part I – Introduction Part II – Foundation   The time has come to talk about controllers in a multi-tenant ASP.NET MVC architecture. This is actually the most critical design decision you will make when dealing with multi-tenancy with MVC. In my design, I took into account the design goals I mentioned in the introduction about inversion of control and what a tenant is to my design. Be aware that this is only one way to achieve multi-tenant controllers.   The Premise MvcEx (which is a sample written by Rob Ashton) utilizes dynamic controllers. Essentially a controller is “dynamic” in that multiple action results can be placed in different “controllers” with the same name. This approach is a bit too complicated for my design. I wanted to stick with plain old inheritance when dealing with controllers. The basic premise of my controller design is that my main host defines a set of universal controllers. It is the responsibility of the tenant to decide if the tenant would like to utilize these core controllers. This can be done either by straight usage of the controller or inheritance for extension of the functionality defined by the controller. The controller is resolved by a StructureMap container that is attached to the tenant, as discussed in Part II.   Controller Resolution I have been thinking about two different ways to resolve controllers with StructureMap. One way is to use named instances. This is a really easy way to simply pull the controller right out of the container without a lot of fuss. I ultimately chose not to use this approach. The reason for this decision is to ensure that the controllers are named properly. If a controller has a different named instance that the controller type, then the resolution has a significant disconnect and there are no guarantees. The final approach, the one utilized by the sample, is to simply pull all controller types and correlate the type with a controller name. This has a bit of a application start performance disadvantage, but is significantly more approachable for maintainability. For example, if I wanted to go back and add a “ControllerName” attribute, I would just have to change the ControllerFactory to suit my needs.   The Code The container factory that I have built is actually pretty simple. That’s really all we need. The most significant method is the GetControllersFor method. This method makes the model from the Container and determines all the concrete types for IController.  The thing you might notice is that this doesn’t depend on tenants, but rather containers. You could easily use this controller factory for an application that doesn’t utilize multi-tenancy. public class ContainerControllerFactory : IControllerFactory { private readonly ThreadSafeDictionary<IContainer, IDictionary<string, Type>> typeCache; public ContainerControllerFactory(IContainerResolver resolver) { Ensure.Argument.NotNull(resolver, "resolver"); this.ContainerResolver = resolver; this.typeCache = new ThreadSafeDictionary<IContainer, IDictionary<string, Type>>(); } public IContainerResolver ContainerResolver { get; private set; } public virtual IController CreateController(RequestContext requestContext, string controllerName) { var controllerType = this.GetControllerType(requestContext, controllerName); if (controllerType == null) return null; var controller = this.ContainerResolver.Resolve(requestContext).GetInstance(controllerType) as IController; // ensure the action invoker is a ContainerControllerActionInvoker if (controller != null && controller is Controller && !((controller as Controller).ActionInvoker is ContainerControllerActionInvoker)) (controller as Controller).ActionInvoker = new ContainerControllerActionInvoker(this.ContainerResolver); return controller; } public void ReleaseController(IController controller) { if (controller != null && controller is IDisposable) ((IDisposable)controller).Dispose(); } internal static IEnumerable<Type> GetControllersFor(IContainer container) { Ensure.Argument.NotNull(container); return container.Model.InstancesOf<IController>().Select(x => x.ConcreteType).Distinct(); } protected virtual Type GetControllerType(RequestContext requestContext, string controllerName) { Ensure.Argument.NotNull(requestContext, "requestContext"); Ensure.Argument.NotNullOrEmpty(controllerName, "controllerName"); var container = this.ContainerResolver.Resolve(requestContext); var typeDictionary = this.typeCache.GetOrAdd(container, () => GetControllersFor(container).ToDictionary(x => ControllerFriendlyName(x.Name))); Type found = null; if (typeDictionary.TryGetValue(ControllerFriendlyName(controllerName), out found)) return found; return null; } private static string ControllerFriendlyName(string value) { return (value ?? string.Empty).ToLowerInvariant().Without("controller"); } } One thing to note about my implementation is that we do not use namespaces that can be utilized in the default ASP.NET MVC controller factory. This is something that I don’t use and have no desire to implement and test. The reason I am not using namespaces in this situation is because each tenant has its own namespaces and the routing would not make sense in this case.   Because we are using IoC, dependencies are automatically injected into the constructor. For example, a tenant container could implement it’s own IRepository and a controller could be defined in the “main” project. The IRepository from the tenant would be injected into the main project’s controller. This is quite a useful feature.   Again, the source code is on GitHub here.   Up Next Up next is the view resolution. This is a complicated issue, so be prepared. I hope that you have found this series useful. If you have any questions about my implementation so far, send me an email or DM me on Twitter. I have had a lot of great conversations about multi-tenancy so far and I greatly appreciate the feedback!

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• Week in Geek: US Govt E-card Scam Siphons Confidential Data Edition

  - by Asian Angel

  This week we learned how to “back up photos to Flickr, automate repetitive tasks, & normalize MP3 volume”, enable “stereo mix” in Windows 7 to record audio, create custom papercraft toys, read up on three alternatives to Apple’s flaky iOS alarm clock, decorated our desktops & app docks with Google icon packs, and more. Photo by alexschlegel. Random Geek Links It has been a busy week on the security & malware fronts and we have a roundup of the latest news to help keep you updated. Photo by TopTechWriter.US. US govt e-card scam hits confidential data A fake U.S. government Christmas e-card has managed to siphon off gigabytes of sensitive data from a number of law enforcement and military staff who work on cybersecurity matters, many of whom are involved in computer crime investigations. Security tool uncovers multiple bugs in every browser Michal Zalewski reports that he discovered the vulnerability in Internet Explorer a while ago using his cross_fuzz fuzzing tool and reported it to Microsoft in July 2010. Zalewski also used cross_fuzz to discover bugs in other browsers, which he also reported to the relevant organisations. Microsoft to fix Windows holes, but not ones in IE Microsoft said that it will release two security bulletins next week fixing three holes in Windows, but it is still investigating or working on fixing holes in Internet Explorer that have been reportedly exploited in attacks. Microsoft warns of Windows flaw affecting image rendering Microsoft has warned of a Windows vulnerability that could allow an attacker to take control of a computer if the user is logged on with administrative rights. Windows 7 Not Affected by Critical 0-Day in the Windows Graphics Rendering Engine While confirming that details on a Critical zero-day vulnerability have made their way into the wild, Microsoft noted that customers running the latest iteration of Windows client and server platforms are not exposed to any risks. Microsoft warns of Office-related malware Microsoft’s Malware Protection Center issued a warning this week that it has spotted malicious code on the Internet that can take advantage of a flaw in Word and infect computers after a user does nothing more than read an e-mail. *Refers to a flaw that was addressed in the November security patch releases. Make sure you have all of the latest security updates installed. Unpatched hole in ImgBurn disk burning application According to security specialist Secunia, a highly critical vulnerability in ImgBurn, a lightweight disk burning application, can be used to remotely compromise a user’s system. Hole in VLC Media Player Virtual Security Research (VSR) has identified a vulnerability in VLC Media Player. In versions up to and including 1.1.5 of the VLC Media Player. Flash Player sandbox can be bypassed Flash applications run locally can read local files and send them to an online server – something which the sandbox is supposed to prevent. Chinese auction site touts hacked iTunes accounts Tens of thousands of reportedly hacked iTunes accounts have been found on Chinese auction site Taobao, but the company claims it is unable to take action unless there are direct complaints. What happened in the recent Hotmail outage Mike Schackwitz explains the cause of the recent Hotmail outage. DOJ sends order to Twitter for Wikileaks-related account info The U.S. Justice Department has obtained a court order directing Twitter to turn over information about the accounts of activists with ties to Wikileaks, including an Icelandic politician, a legendary Dutch hacker, and a U.S. computer programmer. Google gets court to block Microsoft Interior Department e-mail win The U.S. Federal Claims Court has temporarily blocked Microsoft from proceeding with the $49.3 million, five-year DOI contract that it won this past November. Google Apps customers get email lockdown Companies and organisations using Google Apps are now able to restrict the email access of selected users. LibreOffice Is the Default Office Suite for Ubuntu 11.04 Matthias Klose has announced some details regarding the replacement of the old OpenOffice.org 3.2.1 packages with the new LibreOffice 3.3 ones, starting with the upcoming Ubuntu 11.04 (Natty Narwhal) Alpha 2 release. Sysadmin Geek Tips Photo by Filomena Scalise. How to Setup Software RAID for a Simple File Server on Ubuntu Do you need a file server that is cheap and easy to setup, “rock solid” reliable, and has Email Alerting? This tutorial shows you how to use Ubuntu, software RAID, and SaMBa to accomplish just that. How to Control the Order of Startup Programs in Windows While you can specify the applications you want to launch when Windows starts, the ability to control the order in which they start is not available. However, there are a couple of ways you can easily overcome this limitation and control the startup order of applications. Random TinyHacker Links Using Opera Unite to Send Large Files A tutorial on using Opera Unite to easily send huge files from your computer. WorkFlowy is a Useful To-do List Tool A cool to-do list tool that lets you integrate multiple tasks in one single list easily. Playing Flash Videos on iOS Devices Yes, you can play flash videos on jailbroken iPhones. Here’s a tutorial. Clear Safari History and Cookies On iPhone A tutorial on clearing your browser history on iPhone and other iOS devices. Monitor Your Internet Usage Here’s a cool, cross-platform tool to monitor your internet bandwidth. Super User Questions See what the community had to say on these popular questions from Super User this week. Why is my upload speed much less than my download speed? Where should I find drivers for my laptop if it didn’t come with a driver disk? OEM Office 2010 without media – how to reinstall? Is there a point to using theft tracking software like Prey on my laptop, if you have login security? Moving an “all-in-one” PC when turned on/off How-To Geek Weekly Article Recap Get caught up on your HTG reading with our hottest articles from this past week. How to Combine Rescue Disks to Create the Ultimate Windows Repair Disk How To Boot 10 Different Live CDs From 1 USB Flash Drive What is Camera Raw, and Why Would a Professional Prefer it to JPG? Did You Know Facebook Has Built-In Shortcut Keys? The How-To Geek Guide to Audio Editing: The Basics One Year Ago on How-To Geek Enjoy looking through our latest gathering of retro article goodness. Learning Windows 7: Create a Homegroup & Join a New Computer To It How To Disconnect a Machine from a Homegroup Use Remote Desktop To Access Other Computers On a Small Office or Home Network How To Share Files and Printers Between Windows 7 and Vista Allow Users To Run Only Specified Programs in Windows 7 The Geek Note That is all we have for you this week and we hope your first week back at work or school has gone very well now that the holidays are over. Know a great tip? Send it in to us at [email protected]. Photo by Pamela Machado. Latest Features How-To Geek ETC HTG Projects: How to Create Your Own Custom Papercraft Toy How to Combine Rescue Disks to Create the Ultimate Windows Repair Disk What is Camera Raw, and Why Would a Professional Prefer it to JPG? The How-To Geek Guide to Audio Editing: The Basics How To Boot 10 Different Live CDs From 1 USB Flash Drive The 20 Best How-To Geek Linux Articles of 2010 Arctic Theme for Windows 7 Gives Your Desktop an Icy Touch Install LibreOffice via PPA and Receive Auto-Updates in Ubuntu Creative Portraits Peek Inside the Guts of Modern Electronics Scenic Winter Lane Wallpaper to Create a Relaxing Mood Access Your Web Apps Directly Using the Context Menu in Chrome The Deep – Awesome Use of Metal Objects as Deep Sea Creatures [Video]

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• Parallelism in .NET – Part 5, Partitioning of Work

  - by Reed

  When parallelizing any routine, we start by decomposing the problem.  Once the problem is understood, we need to break our work into separate tasks, so each task can be run on a different processing element.  This process is called partitioning. Partitioning our tasks is a challenging feat.  There are opposing forces at work here: too many partitions adds overhead, too few partitions leaves processors idle.  Trying to work the perfect balance between the two extremes is the goal for which we should aim.  Luckily, the Task Parallel Library automatically handles much of this process.  However, there are situations where the default partitioning may not be appropriate, and knowledge of our routines may allow us to guide the framework to making better decisions. First off, I’d like to say that this is a more advanced topic.  It is perfectly acceptable to use the parallel constructs in the framework without considering the partitioning taking place.  The default behavior in the Task Parallel Library is very well-behaved, even for unusual work loads, and should rarely be adjusted.  I have found few situations where the default partitioning behavior in the TPL is not as good or better than my own hand-written partitioning routines, and recommend using the defaults unless there is a strong, measured, and profiled reason to avoid using them.  However, understanding partitioning, and how the TPL partitions your data, helps in understanding the proper usage of the TPL. I indirectly mentioned partitioning while discussing aggregation.  Typically, our systems will have a limited number of Processing Elements (PE), which is the terminology used for hardware capable of processing a stream of instructions.  For example, in a standard Intel i7 system, there are four processor cores, each of which has two potential hardware threads due to Hyperthreading.  This gives us a total of 8 PEs – theoretically, we can have up to eight operations occurring concurrently within our system. In order to fully exploit this power, we need to partition our work into Tasks.  A task is a simple set of instructions that can be run on a PE.  Ideally, we want to have at least one task per PE in the system, since fewer tasks means that some of our processing power will be sitting idle.  A naive implementation would be to just take our data, and partition it with one element in our collection being treated as one task.  When we loop through our collection in parallel, using this approach, we’d just process one item at a time, then reuse that thread to process the next, etc.  There’s a flaw in this approach, however.  It will tend to be slower than necessary, often slower than processing the data serially. The problem is that there is overhead associated with each task.  When we take a simple foreach loop body and implement it using the TPL, we add overhead.  First, we change the body from a simple statement to a delegate, which must be invoked.  In order to invoke the delegate on a separate thread, the delegate gets added to the ThreadPool’s current work queue, and the ThreadPool must pull this off the queue, assign it to a free thread, then execute it.  If our collection had one million elements, the overhead of trying to spawn one million tasks would destroy our performance. The answer, here, is to partition our collection into groups, and have each group of elements treated as a single task.  By adding a partitioning step, we can break our total work into small enough tasks to keep our processors busy, but large enough tasks to avoid overburdening the ThreadPool.  There are two clear, opposing goals here: Always try to keep each processor working, but also try to keep the individual partitions as large as possible. When using Parallel.For, the partitioning is always handled automatically.  At first, partitioning here seems simple.  A naive implementation would merely split the total element count up by the number of PEs in the system, and assign a chunk of data to each processor.  Many hand-written partitioning schemes work in this exactly manner.  This perfectly balanced, static partitioning scheme works very well if the amount of work is constant for each element.  However, this is rarely the case.  Often, the length of time required to process an element grows as we progress through the collection, especially if we’re doing numerical computations.  In this case, the first PEs will finish early, and sit idle waiting on the last chunks to finish.  Sometimes, work can decrease as we progress, since previous computations may be used to speed up later computations.  In this situation, the first chunks will be working far longer than the last chunks.  In order to balance the workload, many implementations create many small chunks, and reuse threads.  This adds overhead, but does provide better load balancing, which in turn improves performance. The Task Parallel Library handles this more elaborately.  Chunks are determined at runtime, and start small.  They grow slowly over time, getting larger and larger.  This tends to lead to a near optimum load balancing, even in odd cases such as increasing or decreasing workloads.  Parallel.ForEach is a bit more complicated, however. When working with a generic IEnumerable<T>, the number of items required for processing is not known in advance, and must be discovered at runtime.  In addition, since we don’t have direct access to each element, the scheduler must enumerate the collection to process it.  Since IEnumerable<T> is not thread safe, it must lock on elements as it enumerates, create temporary collections for each chunk to process, and schedule this out.  By default, it uses a partitioning method similar to the one described above.  We can see this directly by looking at the Visual Partitioning sample shipped by the Task Parallel Library team, and available as part of the Samples for Parallel Programming.  When we run the sample, with four cores and the default, Load Balancing partitioning scheme, we see this: The colored bands represent each processing core.  You can see that, when we started (at the top), we begin with very small bands of color.  As the routine progresses through the Parallel.ForEach, the chunks get larger and larger (seen by larger and larger stripes). Most of the time, this is fantastic behavior, and most likely will out perform any custom written partitioning.  However, if your routine is not scaling well, it may be due to a failure in the default partitioning to handle your specific case.  With prior knowledge about your work, it may be possible to partition data more meaningfully than the default Partitioner. There is the option to use an overload of Parallel.ForEach which takes a Partitioner<T> instance.  The Partitioner<T> class is an abstract class which allows for both static and dynamic partitioning.  By overriding Partitioner<T>.SupportsDynamicPartitions, you can specify whether a dynamic approach is available.  If not, your custom Partitioner<T> subclass would override GetPartitions(int), which returns a list of IEnumerator<T> instances.  These are then used by the Parallel class to split work up amongst processors.  When dynamic partitioning is available, GetDynamicPartitions() is used, which returns an IEnumerable<T> for each partition.  If you do decide to implement your own Partitioner<T>, keep in mind the goals and tradeoffs of different partitioning strategies, and design appropriately. The Samples for Parallel Programming project includes a ChunkPartitioner class in the ParallelExtensionsExtras project.  This provides example code for implementing your own, custom allocation strategies, including a static allocator of a given chunk size.  Although implementing your own Partitioner<T> is possible, as I mentioned above, this is rarely required or useful in practice.  The default behavior of the TPL is very good, often better than any hand written partitioning strategy.

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• Compiling examples for consuming the REST Endpoints for WCF Service using Agatha

  - by REA_ANDREW

  I recently made two contributions to the Agatha Project by Davy Brion over on Google Code, and one of the things I wanted to follow up with was a post showing examples and some, seemingly required tid bits.  The contributions which I made where: To support StructureMap To include REST (JSON and XML) support for the service contract The examples which I have made, I want to format them so they fit in with the current format of examples over on Agatha and hopefully create and submit a third patch which will include these examples to help others who wish to use these additions. Whilst building these examples for both XML and JSON I have learnt a couple of things which I feel are not really well documented, but are extremely good practice and once known make perfect sense.  I have chosen a real basic e-commerce context for my example Requests and Responses, and have also made use of the excellent tool AutoMapper, again on Google Code. Setting the scene I have followed the Pipes and Filters Pattern with the IQueryable interface on my Repository and exposed the following methods to query Products: IQueryable<Product> GetProducts(); IQueryable<Product> ByCategoryName(this IQueryable<Product> products, string categoryName) Product ByProductCode(this IQueryable<Product> products, String productCode) I have an interface for the IProductRepository but for the concrete implementation I have simply created a protected getter which populates a private List<Product> with 100 test products with random data.  Another good reason for following an interface based approach is that it will demonstrate usage of my first contribution which is the StructureMap support.  Finally the two Domain Objects I have made are Product and Category as shown below: public class Product { public String ProductCode { get; set; } public String Name { get; set; } public Decimal Price { get; set; } public Decimal Rrp { get; set; } public Category Category { get; set; } }   public class Category { public String Name { get; set; } }   Requirements for the REST Support One of the things which you will notice with Agatha is that you do not have to decorate your Request and Response objects with the WCF Service Model Attributes like DataContract, DataMember etc… Unfortunately from what I have seen, these are required if you want the same types to work with your REST endpoint.  I have not tried but I assume the same result can be achieved by simply decorating the same classes with the Serializable Attribute.  Without this the operation will fail. Another surprising thing I have found is that it did not work until I used the following Attribute parameters: Name Namespace e.g. [DataContract(Name = "GetProductsRequest", Namespace = "AgathaRestExample.Service.Requests")] public class GetProductsRequest : Request { }   Although I was surprised by this, things kind of explained themselves when I got round to figuring out the exact construct required for both the XML and the REST.  One of the things which you already know and are then reminded of is that each of your Requests and Responses ultimately inherit from an abstract base class respectively. This information needs to be represented in a way native to the format being used.  I have seen this in XML but I have not seen the format which is required for the JSON. JSON Consumer Example I have used JQuery to create the example and I simply want to make two requests to the server which as you will know with Agatha are transmitted inside an array to reduce the service calls.  I have also used a tool called json2 which is again over at Google Code simply to convert my JSON expression into its string format for transmission.  You will notice that I specify the type of Request I am using and the relevant Namespace it belongs to.  Also notice that the second request has a parameter so each of these two object are representing an abstract Request and the parameters of the object describe it. <script type="text/javascript"> var bodyContent = $.ajax({ url: "http://localhost:50348/service.svc/json/processjsonrequests", global: false, contentType: "application/json; charset=utf-8", type: "POST", processData: true, data: JSON.stringify([ { __type: "GetProductsRequest:AgathaRestExample.Service.Requests" }, { __type: "GetProductsByCategoryRequest:AgathaRestExample.Service.Requests", CategoryName: "Category1" } ]), dataType: "json", success: function(msg) { alert(msg); } }).responseText; </script>   XML Consumer Example For the XML Consumer example I have chosen to use a simple Console Application and make a WebRequest to the service using the XML as a request.  I have made a crude static method which simply reads from an XML File, replaces some value with a parameter and returns the formatted XML.  I say crude but it simply shows how XML Templates for each type of Request could be made and then have a wrapper utility in whatever language you use to combine the requests which are required.  The following XML is the same Request array as shown above but simply in the XML Format. <?xml version="1.0" encoding="utf-8" ?> <ArrayOfRequest xmlns="http://schemas.datacontract.org/2004/07/Agatha.Common" xmlns:i="http://www.w3.org/2001/XMLSchema-instance"> <Request i:type="a:GetProductsRequest" xmlns:a="AgathaRestExample.Service.Requests"/> <Request i:type="a:GetProductsByCategoryRequest" xmlns:a="AgathaRestExample.Service.Requests"> <a:CategoryName>{CategoryName}</a:CategoryName> </Request> </ArrayOfRequest>   It is funny because I remember submitting a question to StackOverflow asking whether there was a REST Client Generation tool similar to what Microsoft used for their RestStarterKit but which could be applied to existing services which have REST endpoints attached.  I could not find any but this is now definitely something which I am going to build, as I think it is extremely useful to have but also it should not be too difficult based on the information I now know about the above.  Finally I thought that the Strategy Pattern would lend itself really well to this type of thing so it can accommodate for different languages. I think that is about it, I have included the code for the example Console app which I made below incase anyone wants to have a mooch at the code.  As I said above I want to reformat these to fit in with the current examples over on the Agatha project, but also now thinking about it, make a Documentation Web method…{brain ticking} :-) Cheers for now and here is the final bit of code: static void Main(string[] args) { var request = WebRequest.Create("http://localhost:50348/service.svc/xml/processxmlrequests"); request.Method = "POST"; request.ContentType = "text/xml"; using(var writer = new StreamWriter(request.GetRequestStream())) { writer.WriteLine(GetExampleRequestsString("Category1")); } var response = request.GetResponse(); using(var reader = new StreamReader(response.GetResponseStream())) { Console.WriteLine(reader.ReadToEnd()); } Console.ReadLine(); } static string GetExampleRequestsString(string categoryName) { var data = File.ReadAllText(Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), "ExampleRequests.xml")); data = data.Replace("{CategoryName}", categoryName); return data; } }

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• Parallelism in .NET – Part 14, The Different Forms of Task

  - by Reed

  Before discussing Task creation and actual usage in concurrent environments, I will briefly expand upon my introduction of the Task class and provide a short explanation of the distinct forms of Task.  The Task Parallel Library includes four distinct, though related, variations on the Task class. In my introduction to the Task class, I focused on the most basic version of Task.  This version of Task, the standard Task class, is most often used with an Action delegate.  This allows you to implement for each task within the task decomposition as a single delegate. Typically, when using the new threading constructs in .NET 4 and the Task Parallel Library, we use lambda expressions to define anonymous methods.  The advantage of using a lambda expression is that it allows the Action delegate to directly use variables in the calling scope.  This eliminates the need to make separate Task classes for Action<T>, Action<T1,T2>, and all of the other Action<…> delegate types.  As an example, suppose we wanted to make a Task to handle the ”Show Splash” task from our earlier decomposition.  Even if this task required parameters, such as a message to display, we could still use an Action delegate specified via a lambda: // Store this as a local variable string messageForSplashScreen = GetSplashScreenMessage(); // Create our task Task showSplashTask = new Task( () => { // We can use variables in our outer scope, // as well as methods scoped to our class! this.DisplaySplashScreen(messageForSplashScreen); }); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This provides a huge amount of flexibility.  We can use this single form of task for any task which performs an operation, provided the only information we need to track is whether the task has completed successfully or not.  This leads to my first observation: Use a Task with a System.Action delegate for any task for which no result is generated. This observation leads to an obvious corollary: we also need a way to define a task which generates a result.  The Task Parallel Library provides this via the Task<TResult> class. Task<TResult> subclasses the standard Task class, providing one additional feature – the ability to return a value back to the user of the task.  This is done by switching from providing an Action delegate to providing a Func<TResult> delegate.  If we decompose our problem, and we realize we have one task where its result is required by a future operation, this can be handled via Task<TResult>.  For example, suppose we want to make a task for our “Check for Update” task, we could do: Task<bool> checkForUpdateTask = new Task<bool>( () => { return this.CheckWebsiteForUpdate(); }); Later, we would start this task, and perform some other work.  At any point in the future, we could get the value from the Task<TResult>.Result property, which will cause our thread to block until the task has finished processing: // This uses Task<bool> checkForUpdateTask generated above... // Start the task, typically on a background thread checkForUpdateTask.Start(); // Do some other work on our current thread this.DoSomeWork(); // Discover, from our background task, whether an update is available // This will block until our task completes bool updateAvailable = checkForUpdateTask.Result; This leads me to my second observation: Use a Task<TResult> with a System.Func<TResult> delegate for any task which generates a result. Task and Task<TResult> provide a much cleaner alternative to the previous Asynchronous Programming design patterns in the .NET framework.  Instead of trying to implement IAsyncResult, and providing BeginXXX() and EndXXX() methods, implementing an asynchronous programming API can be as simple as creating a method that returns a Task or Task<TResult>.  The client side of the pattern also is dramatically simplified – the client can call a method, then either choose to call task.Wait() or use task.Result when it needs to wait for the operation’s completion. While this provides a much cleaner model for future APIs, there is quite a bit of infrastructure built around the current Asynchronous Programming design patterns.  In order to provide a model to work with existing APIs, two other forms of Task exist.  There is a constructor for Task which takes an Action<Object> and a state parameter.  In addition, there is a constructor for creating a Task<TResult> which takes a Func<Object, TResult> as well as a state parameter.  When using these constructors, the state parameter is stored in the Task.AsyncState property. While these two overloads exist, and are usable directly, I strongly recommend avoiding this for new development.  The two forms of Task which take an object state parameter exist primarily for interoperability with traditional .NET Asynchronous Programming methodologies.  Using lambda expressions to capture variables from the scope of the creator is a much cleaner approach than using the untyped state parameters, since lambda expressions provide full type safety without introducing new variables.

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• Parallelism in .NET – Part 15, Making Tasks Run: The TaskScheduler

  - by Reed

  In my introduction to the Task class, I specifically made mention that the Task class does not directly provide it’s own execution.  In addition, I made a strong point that the Task class itself is not directly related to threads or multithreading.  Rather, the Task class is used to implement our decomposition of tasks.  Once we’ve implemented our tasks, we need to execute them.  In the Task Parallel Library, the execution of Tasks is handled via an instance of the TaskScheduler class. The TaskScheduler class is an abstract class which provides a single function: it schedules the tasks and executes them within an appropriate context.  This class is the class which actually runs individual Task instances.  The .NET Framework provides two (internal) implementations of the TaskScheduler class. Since a Task, based on our decomposition, should be a self-contained piece of code, parallel execution makes sense when executing tasks.  The default implementation of the TaskScheduler class, and the one most often used, is based on the ThreadPool.  This can be retrieved via the TaskScheduler.Default property, and is, by default, what is used when we just start a Task instance with Task.Start(). Normally, when a Task is started by the default TaskScheduler, the task will be treated as a single work item, and run on a ThreadPool thread.  This pools tasks, and provides Task instances all of the advantages of the ThreadPool, including thread pooling for reduced resource usage, and an upper cap on the number of work items.  In addition, .NET 4 brings us a much improved thread pool, providing work stealing and reduced locking within the thread pool queues.  By using the default TaskScheduler, our Tasks are run asynchronously on the ThreadPool. There is one notable exception to my above statements when using the default TaskScheduler.  If a Task is created with the TaskCreationOptions set to TaskCreationOptions.LongRunning, the default TaskScheduler will generate a new thread for that Task, at least in the current implementation.  This is useful for Tasks which will persist for most of the lifetime of your application, since it prevents your Task from starving the ThreadPool of one of it’s work threads. The Task Parallel Library provides one other implementation of the TaskScheduler class.  In addition to providing a way to schedule tasks on the ThreadPool, the framework allows you to create a TaskScheduler which works within a specified SynchronizationContext.  This scheduler can be retrieved within a thread that provides a valid SynchronizationContext by calling the TaskScheduler.FromCurrentSynchronizationContext() method. This implementation of TaskScheduler is intended for use with user interface development.  Windows Forms and Windows Presentation Foundation both require any access to user interface controls to occur on the same thread that created the control.  For example, if you want to set the text within a Windows Forms TextBox, and you’re working on a background thread, that UI call must be marshaled back onto the UI thread.  The most common way this is handled depends on the framework being used.  In Windows Forms, Control.Invoke or Control.BeginInvoke is most often used.  In WPF, the equivelent calls are Dispatcher.Invoke or Dispatcher.BeginInvoke. As an example, say we’re working on a background thread, and we want to update a TextBlock in our user interface with a status label.  The code would typically look something like: // Within background thread work... string status = GetUpdatedStatus(); Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action( () => { statusLabel.Text = status; })); // Continue on in background method .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This works fine, but forces your method to take a dependency on WPF or Windows Forms.  There is an alternative option, however.  Both Windows Forms and WPF, when initialized, setup a SynchronizationContext in their thread, which is available on the UI thread via the SynchronizationContext.Current property.  This context is used by classes such as BackgroundWorker to marshal calls back onto the UI thread in a framework-agnostic manner. The Task Parallel Library provides the same functionality via the TaskScheduler.FromCurrentSynchronizationContext() method.  When setting up our Tasks, as long as we’re working on the UI thread, we can construct a TaskScheduler via: TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); We then can use this scheduler on any thread to marshal data back onto the UI thread.  For example, our code above can then be rewritten as: string status = GetUpdatedStatus(); (new Task(() => { statusLabel.Text = status; })) .Start(uiScheduler); // Continue on in background method This is nice since it allows us to write code that isn’t tied to Windows Forms or WPF, but is still fully functional with those technologies.  I’ll discuss even more uses for the SynchronizationContext based TaskScheduler when I demonstrate task continuations, but even without continuations, this is a very useful construct. In addition to the two implementations provided by the Task Parallel Library, it is possible to implement your own TaskScheduler.  The ParallelExtensionsExtras project within the Samples for Parallel Programming provides nine sample TaskScheduler implementations.  These include schedulers which restrict the maximum number of concurrent tasks, run tasks on a single threaded apartment thread, use a new thread per task, and more.

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