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  • Make Python Socket Server More Efficient

    - by BenMills
    I have very little experience working with sockets and multithreaded programming so to learn more I decided to see if I could hack together a little python socket server to power a chat room. I ended up getting it working pretty well but then I noticed my server's CPU usage spiked up over 100% when I had it running in the background. Here is my code in full: http://gist.github.com/332132 I know this is a pretty open ended question so besides just helping with my code are there any good articles I could read that could help me learn more about this? My full code: import select import socket import sys import threading from daemon import Daemon class Server: def __init__(self): self.host = '' self.port = 9998 self.backlog = 5 self.size = 1024 self.server = None self.threads = [] self.send_count = 0 def open_socket(self): try: self.server = socket.socket(socket.AF_INET6, socket.SOCK_STREAM) self.server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) self.server.bind((self.host,self.port)) self.server.listen(5) print "Server Started..." except socket.error, (value,message): if self.server: self.server.close() print "Could not open socket: " + message sys.exit(1) def remove_thread(self, t): t.join() def send_to_children(self, msg): self.send_count = 0 for t in self.threads: t.send_msg(msg) print 'Sent to '+str(self.send_count)+" of "+str(len(self.threads)) def run(self): self.open_socket() input = [self.server,sys.stdin] running = 1 while running: inputready,outputready,exceptready = select.select(input,[],[]) for s in inputready: if s == self.server: # handle the server socket c = Client(self.server.accept(), self) c.start() self.threads.append(c) print "Num of clients: "+str(len(self.threads)) self.server.close() for c in self.threads: c.join() class Client(threading.Thread): def __init__(self,(client,address), server): threading.Thread.__init__(self) self.client = client self.address = address self.size = 1024 self.server = server self.running = True def send_msg(self, msg): if self.running: self.client.send(msg) self.server.send_count += 1 def run(self): while self.running: data = self.client.recv(self.size) if data: print data self.server.send_to_children(data) else: self.running = False self.server.threads.remove(self) self.client.close() """ Run Server """ class DaemonServer(Daemon): def run(self): s = Server() s.run() if __name__ == "__main__": d = DaemonServer('/var/servers/fserver.pid') if len(sys.argv) == 2: if 'start' == sys.argv[1]: d.start() elif 'stop' == sys.argv[1]: d.stop() elif 'restart' == sys.argv[1]: d.restart() else: print "Unknown command" sys.exit(2) sys.exit(0) else: print "usage: %s start|stop|restart" % sys.argv[0] sys.exit(2)

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  • ThreadAbortException (WebClient using DownloadFile to grab file from server)

    - by baron
    Hi Everyone, Referencing my Earlier Question, regarding downloading a file from a server and handling exceptions properly. I am positive that I had this solved, then in classic programming fashion, returned days later to frustratingly find it broken :-( Updated code: private static void GoGetIt(HttpContext context) { var directoryInfoOfWhereTheDirectoryFullOfFilesShouldBe = new FileInfo(......); var name = SomeBasicLogicToDecideName(); //if (!directoryInfoOfWhereTheDirectoryFullOfFilesShouldBe.RefreshExists()) //{ // throw new Exception(string.Format("Could not find {0}.", name)); //} var tempDirectory = ""; //Omitted - creates temporary directory try { directoryInfoOfWhereTheDirectoryFullOfFilesShouldBe.CopyAll(tempDirectory); var response = context.Response; response.ContentType = "binary/octet-stream"; response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}.zip", name)); ZipHelper.ZipDirectoryToStream(tempDirectory, response.OutputStream); response.End(); } catch (Exception ex) { Debug.WriteLine(ex.ToString()); context.Response.StatusCode = 404; } finally { tempDirectory.DeleteWithPrejudice(); } } This was working fine, and returning the zip, otherwise if the file didn't exist returning 404. Then on the client side I could handle this: public bool Download() { try { using (var client = new WebClient()) { client.DownloadFile(name, tempFilePath); } } catch (Exception) { fileExists = false; } return fileExists; } But the problem now is two things. 1) I get System.Threading.ThreadAbortException: Thread was being aborted in the server side try-catch block. Usually this was just a file not found exception. I have no idea what or why that new exception is throwing? 2) Now that a different exception is throwing on the server side instead of the file not found, it would seem I can't use this set up for the application, because back on client side, any exception is assumed to be filenotfound. Any help, especially info on why this ThreadAbortException is throwing!?!? greatly appreciated. Cheers

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  • Why isn't the background image showing up on my webpage?

    - by William
    okay, so I'm trying to set up a webpage with a div wrapping two other divs, and the wrapper div has a background, and the other two are transparent. How come this isn't working? here is the CSS: .posttext{ float: left; width: 70%; text-align: left; padding: 5px; background-color: !important #transparent; } .postavi{ float: left; width: 100px; height: 100%; text-align: left; background-color: #transparent; padding: 5px; } .postwrapper{ background-image:url('images/post_bg.png'); background-position:left top; background-repeat:repeat-y; } and here is the HTML: <div class="postwrapper"> <div class="postavi"><img src="http://prime.programming-designs.com/test_forum/images/avatars/hacker.png" alt="hacker"/></div><div class="posttext"><p style="color: #ff0066">You will have bad luck today.</p>lol</div> </div>

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  • Useful training courses that aren't specific to a single technology

    - by Dave Turvey
    I have possibly the best problem in the world. I have about £1600 left in a training budget and I need to find something to spend it on. I can spend it on anything that could be considered training. Books, courses, conferences, etc. I would like to find a course that would benifit a software developer but is not about learning a specific programming technology. I don't really want to spend it on a technical training course. These topics are usually best learned with a good book and some trial and error. I have also already been on a general business/management training course and a PRINCE2 project management course. I am currently working on a project on my own so am responsible for communicating with the client, requirements gathering, project management, etc., as well as the coding. What training have you found useful outside the usual technical stuff? Has anyone done any business analysis courses? What were they like? Are there any courses on some of the practicalities of working with software, e.g. automated test and deployment strategies, handling technical support? I would prefer a course in the UK but I can travel if necessary.

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  • Front End Developer v/s PHP-MySQL Engineer

    - by user301943
    Hello, I want to decide which of this would be a more viable career option? I am ready to quit my current job and hence I am looking for new opportunity. Current job is maintainence and no more active development. My current role is of a PHP/MySQL Developer. I very well understand web-programming and am comfortable with RoR/Sinatra/Zend MVC/JQuery/JSON manipulation, etc. I understand MySQL InnoDB/MyISAM engine and how one differs from the other, etc. Basically, I could very well manage the deployment of a web-application end-to-end including configuration of Apache/Nginx servers, memcache,etc On the other hand, I am being offered a Sr.Front End Web developer that would require me to extensively write HTML/CSS crossbrowser/crossplatform compliant code. I very well understand XHTML/CSS/Box model etc. I would be working on Drupal for the management of websites. While I understand continuing to work on server-side technologies would always be a good career path, how would the role of Core front-end developer turn out to be? If I take this opportunity, will I eventually get a chance to focus onto UCD, HCI, Information Architect,etc. So are these kinda roles possible if I focus on front end development? No offenses to the Front end developers, just want to understand if this is something I want to gain a mastery over. I have 2 yrs of industry experience after graduating with a MS-Computer Science. Although, I have a CS degree, if I were to take uip serious front-end role; I could probably go back and take up some design/HCI/UI courses. Please advise.

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  • multi thread apps crashes in release mode

    - by etzarfat
    Hello, I'm using Visual Studio 2008 (programming in c). I've a weird problem I worte a program that has 2 threads that runs simultaneously, a recording thread (using audio card to record into memory) and a translation thread (using a speech engine to recognize the words). when I run my program in debug mode (aka setting a breakpoint in the code) it runs great, however when I run in debug mode or release mode (outside the visual studio enviroment) it crashes and give me the following exception: "Unhandled exception at 0x7c911129 in LowLevel.exe: 0xC0000005: Access violation reading location 0x014c7245." My stack looks: LowLevel.exe!__set_flsgetvalue() Line 256 + 0xc bytes C LowLevel.exe!_isleadbyte_l(int c=4359676, localeinfo_struct * plocinfo=0x00000001) Line 57 C++ 014b00d8() LowLevel.exe!PlayDateOfExam(int option=1) Line 2240 + 0x7 bytes C++ LowLevel.exe!NSCThread(void * arg=0x00000000) Line 1585 + 0xb bytes C++ kernel32.dll!7c80b729() winmm.dll!76b5b294() I uses the following file in my project "nsc.lib" and WinMM.lib" I'm not really familiar with threads I used a sample (which works great) and built on it. I saw a similiar question year on the forum but I didn't really understand the answers since I'm not familiar with with threads. Can someone help me? Thanks

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  • New at Python: GLPK not building properly / Python ImportError

    - by Merjit
    This is a beginner question, and a follow-up to this one, where I was pointed to GLPK. I'm trying to get PyGLPK, a Python binding for the GNU Linear Programming Kit up and running, but no matter what I do, I can't seem to build and install GLPK so that Python finds it correctly. This comes after running ./configure, make, and sudo make install on the GLPK libraries, and following the instructions for PyGLPK. Specifically, here is the error I get: >>> import glpk Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site- packages/glpk.so, 2): Symbol not found: __glp_lpx_print_ips Referenced from: /Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/glpk.so Expected in: dynamic lookup I assume that something isn't linking to somewhere else, and that it probably has something to do with paths and environment variables. However, here's where my abilities in the shell fail, and I'm at a loss over what to do next. Again, there is probably a simple answer to this, but I haven't had any luck with Google using the terminology I know.

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  • Maths Question: number of different permutations

    - by KingCong
    This is more of a maths question than programming but I figure a lot of people here are pretty good at maths! :) My question is: Given a 9 x 9 grid (81 cells) that must contain the numbers 1 to 9 each exactly 9 times, how many different grids can be produced. The order of the numbers doesn't matter, for example the first row could contain nine 1's etc. This is related to Sudoku and we know the number of valid Sudoku grids is 6.67×10^21, so since my problem isn't constrained like Sudoku by having to have each of the 9 numbers in each row, column and box then the answer should be greater than 6.67×10^21. My first thought was that the answer is 81! however on further reflection this assume that the 81 number possible for each cell are different, distinct number. They are not, there are 81 possible numbers for each cell but only 9 possible different numbers. My next thought was then that each of the cells in the first row can be any number between 1 and 9. If by chance the first row happened to be all the same number, say all 1s, then each cell in the second row could only have 8 possibilites, 2-9. If this continued down until the last row then number of different permutations could be calculated by 9^2 * 8^2 * 7^2 ..... * 1^2. However this doesn't work if each row doesn't contain 9 of the same number. It's been quite a while since I studied this stuff and I can't think of a way to work it out, I'd appreciate any help anyone can offer.

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  • Always can't separate these guys: ascending and descending! Are there good examples?

    - by mystify
    As a non-english dude, I have trouble differentiating this. When I try to translate this into my language, I get something weird like "go up" for ascending. So lets say I want to sort the names of all my pets alphabetically. I want that A comes first, then B, then C... and so on. So since the alphabet is not a number for me, my brain refuses to grok what's "going up". A = 0? B = 1? C = 2? If yes, then ascending would be what I'm most of the time looking for. Table would start showing A, then B, then C... Or is that the other way around? Must I look from the bottom of the table, up? And with numbers: If it's an ascending order, the smallest comes first? (would seem logical...) Can someone post a short but good example for what is an ascending sort order, and what is an descending sort order? And does that apply to whatever platform, programming language, API, etc.?

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  • Calling AddEventListener in a loop with a variable element name

    - by user302209
    Hi, I'm trying to do the following: I have a set of images and select (dropdown) HTML elements, 30 of each one. I'm trying to use AddEventListener on a loop from 1 to 30 so that when I change the value of the select, the image src is updated (and the image changes). The AddEventListener function is this one: function AddEventListener(element, eventType, handler, capture) { if (element.addEventListener) element.addEventListener(eventType, handler, capture); else if (element.attachEvent) element.attachEvent("on" + eventType, handler); } I tried this and it worked: var urlfolderanimalimages = "http://localhost/animalimages/"; var testselect = "sel15"; var testimg = "i15"; AddEventListener(document.getElementById(testselect), "change", function(e) { document.getElementById(testimg).src = urlfolderanimalimages + document.getElementById(testselect).value; document.getElementById(testimg).style.display = 'inline'; if (e.preventDefault) e.preventDefault(); else e.returnResult = false; if (e.stopPropagation) e.stopPropagation(); else e.cancelBubble = true; }, false); But then I tried to call it in a loop and it doesn't work. The event is added, but when I change any select, it will update the last one (the image with id i30). var urlfolderanimalimages = "http://localhost/animalimages/"; for (k=1;k<=30;k++) { var idselect = "sel" + k; var idimage = "i" + k; AddEventListener(document.getElementById(idselect), "change", function(e) { document.getElementById(idimage).src = urlfolderanimalimages + document.getElementById(idselect).value; document.getElementById(idimage).style.display = 'inline'; if (e.preventDefault) e.preventDefault(); else e.returnResult = false; if (e.stopPropagation) e.stopPropagation(); else e.cancelBubble = true; }, false); } What am I doing wrong? I'm new to JavaScript (and programming in general), so sorry for the vomit-inducing code :(

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  • Cocoa NSStream TCP connection to FTP

    - by Chuck
    Hi, I'm new to Cocoa, but not to programming. Recently I decided I wanted to write a FTP client for Mac, and so I first made it in the language I'm most comfortable in (on Windows), and then moved on to Cocoa when I had the workings of FTP communications down. My question is (apparently) a bit controversial: How do I establish a read/writeable connection to (a ftp server)? What I have so far (non working obviously): NSInputStream *iStream; NSOutputStream *oStream; NSHost *host = [NSHost hostWithAddress:@"127.0.0.1"]; [NSStream getStreamsToHost:host port:3333 inputStream:&iStream outputStream:&oStream]; // ftp port: 3333 [iStream retain]; [oStream retain]; [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [oStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [iStream setDelegate:self]; [oStream setDelegate:self]; // which is not implemented apparently [iStream open]; [oStream open]; // .... [iStream write: (const uint8_t *)buf maxLength:8]; Which is partially based on http://developer.apple.com/mac/library/documentation/cocoa/Conceptual/Streams/Articles/NetworkStreams.html Now, why have I chosen NSStream? Because while this question is merely about how to connect to a FTP stream, my whole project will also include SSL and as far as I've been able to search here and on google, NSStream is capable of "switching" to a SSL connection. I've not been able to see the connection being made (which I'm usually able to do), but I also heard something about having to write to the stream before the stream will open? Any pointers are greatly appreciated, and sorry if my question is annoying - I'm new to Cocoa :)

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  • An alternative to reading input from Java's System.in

    - by dvanaria
    I’m working on the UVa Online Judge problem set archive as a way to practice Java, and as a way to practice data structures and algorithms in general. They give an example input file to submit to the online judge to use as a starting point (it’s the solution to problem 100). Input from the standard input stream (java.lang.System.in) is required as part of any solution on this site, but I can’t understand the implementation of reading from System.in they give in their example solution. It’s true that the input file could consist of any variation of integers, strings, etc, but every solution program requires reading basic lines of text input from System.in, one line at a time. There has to be a better (simpler and more robust) method of gathering data from the standard input stream in Java than this: public static String readLn(int maxLg) { byte lin[] = new byte[maxLg]; int lg = 0, car = -1; String line = “”; try { while (lg < maxLg) { car = System.in.read(); if ((car < 0) || (car == ‘\n’)) { break; } lin[lg++] += car; } } catch (java.io.IOException e) { return (null); } if ((car < 0) && (lg == 0)) { return (null); // eof } return (new String(lin, 0, lg)); } I’m really surprised by this. It looks like something pulled directly from K&R’s “C Programming Language” (a great book regardless), minus the access level modifer and exception handling, etc. Even though I understand the implementation, it just seems like it was written by a C programmer and bypasses most of Java’s object oriented nature. Isn’t there a better way to do this, using the StringTokenizer class or maybe using the split method of String or the java.util.regex package instead?

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  • Beginner video capture and processing/Camera selection

    - by mattbauch
    I'll soon be undertaking a research project in real-time event recognition but have no experience with the programming aspect of video capture (I'm an upperclassman undergraduate in computer engineering). I want to start off on the right foot so advice from anyone with experience would be great. The ultimate goal is to track events such as a person standing up/sitting down, entering/leaving a room, possibly even shrugging/slumping in posture, etc. from a security camera-like vantage point. First of all, which cameras/companies would you recommend? I'm looking to spend ~$100, more if necessary but not much. Great resolution isn't a must, but is desirable if affordable. What about IP network cameras vs. a USB type webcam? Webcams are less expensive, but IP cameras seem like they'd be much less work to deal with in software. What features should I look for in the camera? Once I've selected a camera, what does converting its output to a series of RGB bitmaps entail? I've never dealt with video encoding/decoding so a starting point or a tutorial that will guide me up to this point would be great if anyone has suggestions. Finally, what is the best (least complicated/most efficient) way to display video from the camera plus my own superimposed images (boxes around events in progress, for instance) in a GUI application? I can work on any operating system in any language. I have some experience with win32 GUIs and Java GUIs. The focus of the project is on the algorithm and so I'm trying to get the video capture/display portion of the app done cleanly and quickly. Thanks for any responses!!

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  • Highlighting a Table Correctly Despite rowspan and colspan attributes - WITHOUT jQuery

    - by ScottSEA
    Thanks to some !#$#@ in another department who wrote some crap code, I am unable to use the jQuery library - despite my fervent desire to do so. Their software has already been released into the world, and I have to be compatible. ============================================ I am trying to highlight a table. Desired behavior: Clicking on a cell in the body highlights the row. Clicking on a cell in the head highlights the column. If a column and row are both highlighted, the intersection is highlighted a different color (super-highlight). Clicking on a previously super-highlighted cell turns off the highlights. This behavior is simple enough to do with a basic table, but when rowspans and colspans start rearing their ugly heads, things start to get a little wonky... highlighting cell[5], for instance, no longer works reliably. My thought, in order to speed execution time of the highlighting itself (by changing a class name), is to pre-calculate the 'offsets' of all cells - with a 'colStart' and 'colEnd', 'rowStart' and 'rowEnd' when the page loads and store that in an array somehow. The question: How would YOU implement this functionality? I am fairly rusty at my JavaScript, awfully rudimentary in my programming skills and would benefit greatly from some guidance. Thanks, Scott.

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  • Advice for Windows XP Scripting, WSH versus PowerShell

    - by Greg Graham
    After much experience scripting in the Unix/Linux open-source world, using languages such as Bourne Shell, Perl, Python, and Ruby, I now find myself needing to do some Windows XP admin scripting. It appears that the legacy environment is Windows Script Host (WSH), which can use various scripting languages, but the primary language is VBScript, and is based on COM objects. However, the future appears to be Windows PowerShell, which is based on .NET. I haven't done Basic since Applesoft in the 70s, so I'm not keen on learning VBScript, although I did learn enough to write a small script to mount network drives. If I'm going to spend time to really learn this, I'm leaning towards investing my time in the .NET PowerShell environment, if it truly is the future. I did some C# Windows Forms programming a couple of years ago, so I have some exposure to .NET, which also makes PowerShell attractive. Understanding that no one has a crystal ball to predict the future of Microsoft, I would like hear from anyone who is a PowerShell user and thinks it's worthwhile, or if there is anyone that knows of serious drawbacks to PowerShell, and recommends that I stay away from it. Update: I ended up using WSH/VBScript for a particular script that I am installing as a startup script on user's Windows XP workstations. All I have to do is copy it to their Startup folder, and I'm done. However, I only learned enough WSH to accomplish this one job. I am glad to see that PowerShell is the future, and when I have more complicated scripting tasks, I'll to turn PowerShell.

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  • How important is managing memory in Objective-C?

    - by Alex Mcp
    Background: I'm (jumping on the bandwagon and) starting learning about iPhone/iPad development and Objective-C. I have a great background in web development and most of my programming is done in javascript (no libraries), Ruby, and PHP. Question: I'm learning about allocating and releasing memory in Objective-C, and I see it as quite a tricky task to layer on top of actually getting the farking thing to run. I'm trying to get a sense of applications that are out there and what will happen with a poorly memory-managed program. A) Are apps usually released with no memory leaks? Is this a feasible goal, or do people more realistically just excise the worst offenders and that's ok? B) If I make an NSString for a title of a view, let's say, and forget to deallocate it it, does this really only become a problem if I recreate that string repeatedly? I imagine what I'm doing is creating an overhead of the memory needed to store that string, so it's probably quite piddling (a few bytes?) However if I have a rapidly looping cycle in a game that 'leaks' an int every cycle or something, that would overflow the app quite quickly. Are these assumptions correct? Sorry if this isn't up the community-wiki alley, I'm just trying to get a handle on how to think about memory and how careful I'll need to be. Any anecdotes or App Store-submitted app experiences would be awesome to hear as well.

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  • Is it a good practice to suppress warnings?

    - by Chris Cooper
    Sometimes while writing Java in Eclipse, I write code that generates warnings. A common one is this, which I get when extending the Exception class: public class NumberDivideException extends Exception { public NumberDivideException() { super("Illegal complex number operation!"); } public NumberDivideException(String s) { super(s); } } // end NumberDivideException The warning: The serializable class NumberDivideException does not declare a static final serialVersionUID field of type long. I know this warning is caused by my failure to... well, it says right above. I could solve it by including the serialVersionUID, but this is a one hour tiny assignment for school; I don't plan on serializing it anytime soon... The other option, of course, is to let Eclipse add @SuppressWarnings("serial"). But every time my mouse hovers over the Suppress option, I feel a little guilty. For programming in general, is it a good habit to suppress warnings? (Also, as a side question, is adding a "generated" serialVersionUID like serialVersionUID = -1049317663306637382L; the proper way to add a serialVersionUID, or do I have to determine the number some other way?)

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  • WCF, ASMX Basic HTTP binding and IIS

    - by Brennan Mann
    Hello, I have been doing a lot of work with WCF "self" hosted applications. I recently was requested to write a web service where the calling client was a Linux based program named "WGET". I would like to use WCF instead of a traditional ASMX web service. The web service is returning a standard XML response. I am not sure of the underlining details between the two technologies but I know WCF is the proper route. I created a WCF service to be hosted in IIS ( using basicHttpBinding). 1.) Did classic ASMX web services ( standard HTTP POST/GET) use SOAP to return responses? I created an class from XSD for the web service response. What is really going on behind the scenes? Is there just special XML HTTP headers that know how to handle to response? Is the response not wrapped in SOAP? The traditional ASMX web service worked perfectly with the class I generated using the .Net "XSD" program. 2.) I want to use WCF for this service. Will using basicHttpBinding work? As I have read, that is the correct binding to use for ASMX clients. Does this use SOAP, standard HTTP headers, or something else? 3.) This is a dumb question because I have not done a lot of web service programming. I noticed on the ASMX default landing page there were examples for responses and code to invoke the functionality. When I create the same service using WCF, I had to create a client application to perform these tasks. Is there a way to expose the WCF endpoint like a classic ASMX service or is the WSDL the only route? As always, I really appreciate the feedback. Thanks, Brennan

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  • Android - need UI help/advice

    - by Donal Rafferty
    I have been working on Android for the past couple of months getting to know how various components work. One area I am completely lacking in knowledge is any sort of User Interface or graphical interface creation. As an excercise I have been asked to break down the HTC call screen into what components it contains and rebuild as close as possible. Here is a picture of the HTC call screen: From my understanding the above UI has a custom title bar where "Meteor" and the call time appears. Then the main image in the middle block along with a text view showing the called party, in this case "Voice Mail" and the number. The bottom is then a custom view maybe with three custom buttons used within it. Would I be correct in my above assumptions? So the parts I should look into start programming are a custom title bar and a custom view with three custom buttons to place at the bottom? What layout would be reccomended? I hope this question is seen as relative to Stack Overflow, if it is not then I will delete it. Thanks in advance

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  • Turing Model Vs Von Neuman model

    - by Santhosh
    First some background (based on my understanding).. The Von-Neumann architecture describes the stored-program computer where instructions and data are stored in memory and the machine works by changing it's internal state, i.e an instruction operated on some data and modifies the data. So inherently, there is state msintained in the system. The Turing machine architecture works by manipulating symbols on a tape. i.e A tape with infinite number of slots exists, and at any one point in time, the Turing machine is in a particular slot. Based on the symbol read at that slot, the machine change the symbol and move to a different slot. All of this is deterministic. My questions are Is there any relation between these two models (Was the Von Neuman model based on or inspired by the Turing model)? Can we say that Turing model is a superset of Von Newman model? Does functional Programming fit into Turing model. If so how? (I assume FP does not lend itself nicely to the Von Neuman model)

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  • WCF: WTF! Does WCF raise the bar or just the complexity level?

    - by rp
    I understand the value of the three-part service/host/client model offered by WCF. But is it just me or does it seem like WCF took something pretty direct and straightforward (the ASMX model) and made a mess out of it? Is there an alternative to using SvcUtil's command line step back in time to generate the proxy? With ASMX services a test harness was automatically provided; is there a good alternative today with WCF? I appreciate that the WS* stuff is more tightly integrated with WCF and hope to find some payoff for WCF there, but geeze, otherwise I'm perplexed. Also, the state of books available for WCF is abysmal at best. Juval Lowy, a superb author, has written a good O'Reilly reference book "Programming WCF Services" but it doesn't do that much (for me anyway) for learning now to use WCF. That book's precursor (and a little better organized, but not much, as a tutorial) is Michele Leroux Bustamante's Learning WCF. It has good spots but is outdated in place and its corresponding Web site is gone. Do you have good WCF learning references besides just continuing to Google the bejebus out of things? Thanks, rp

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  • Scalable / Parallel Large Graph Analysis Library?

    - by Joel Hoff
    I am looking for good recommendations for scalable and/or parallel large graph analysis libraries in various languages. The problems I am working on involve significant computational analysis of graphs/networks with 1-100 million nodes and 10 million to 1+ billion edges. The largest SMP computer I am using has 256 GB memory, but I also have access to an HPC cluster with 1000 cores, 2 TB aggregate memory, and MPI for communication. I am primarily looking for scalable, high-performance graph libraries that could be used in either single or multi-threaded scenarios, but parallel analysis libraries based on MPI or a similar protocol for communication and/or distributed memory are also of interest for high-end problems. Target programming languages include C++, C, Java, and Python. My research to-date has come up with the following possible solutions for these languages: C++ -- The most viable solutions appear to be the Boost Graph Library and Parallel Boost Graph Library. I have looked briefly at MTGL, but it is currently slanted more toward massively multithreaded hardware architectures like the Cray XMT. C - igraph and SNAP (Small-world Network Analysis and Partitioning); latter uses OpenMP for parallelism on SMP systems. Java - I have found no parallel libraries here yet, but JGraphT and perhaps JUNG are leading contenders in the non-parallel space. Python - igraph and NetworkX look like the most solid options, though neither is parallel. There used to be Python bindings for BGL, but these are now unsupported; last release in 2005 looks stale now. Other topics here on SO that I've looked at have discussed graph libraries in C++, Java, Python, and other languages. However, none of these topics focused significantly on scalability. Does anyone have recommendations they can offer based on experience with any of the above or other library packages when applied to large graph analysis problems? Performance, scalability, and code stability/maturity are my primary concerns. Most of the specialized algorithms will be developed by my team with the exception of any graph-oriented parallel communication or distributed memory frameworks (where the graph state is distributed across a cluster).

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  • pushViewController Not Displaying UIView/Nib with tabbar and nav bar

    - by james
    I'm relatively new to objective c but not programming and am stuck with my iphone app. I created a nav based app with both a navbar and a tab bar controller. I set the tab bar as the root controller. I'm able to switch between each tab without any issues to various UIViews and UITableViews. My issue is that in one of my UITableViews that I call from the TabBarController, didSelectRowAtIndexPath function is suppose to display a new UIView. The below code does not give any errors and runs fine but does not show the new Nib. if(newViewController == nil) { NSLog(@"yes nil"); BookViewController *aNewViewController = [[BookViewController alloc] initWithNibName:@"BookOptionView" bundle:nil]; self.newViewController = aNewViewController; [aNewViewController release]; } BookAppDelegate *delegate = (BookAppDelegate *)[[UIApplication sharedApplication] delegate]; [delegate.appNavBar pushViewController:newViewController animated:YES]; Now when I do the below, it works fine but it gets rid of the nav and tab which I'm assuming because its a modal call instead of pushing the view controller. BookViewController *screen = [[BookViewController alloc] initWithNibName:@"BookOptionView" bundle:[NSBundle mainBundle]]; screen.modalTransitionStyle = UIModalTransitionStyleCoverVertical; [self presentModalViewController:screen animated:YES]; [screen release]; Any ideas why I can't get the View Controller to push correctly? In my application delegate file, I declared an AppNavBarController object (inherit from UINavigationController) called appNavBar. Any help would be appreciated!

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  • Cache efficient code

    - by goldenmean
    This could sound a subjective question, but what i am looking for is specific instances which you would have encountered related to this. 1) How to make a code, cache effective-cache friendly? (More cache hits, as less cahce misses as possible). from both perspectives, data cache & program cache(instruction cache). i.e. What all things in one's code, related to data structures, code constructs one should take care of to make it cache effective. 2) Are there any particular data structures one must use, must avoid,or particular way of accessing the memers of that structure etc.. to make code cache effective. 3) Are there any program constructs(if, for, switch, break, goto,...), code-flow(for inside a if, if inside a for, etc...) one should follow/avoid in this matter? I am looking forward to hear individual experiences related to making a cache efficient code in general. It can be any programming language(C,C++,ASsembly,...), any hardware target(ARM,Intel,PowerPC,...), any OS(Windows,Linux,Symbian,...) etc.. More the variety, it will help better to understand it deeply.

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  • Blackberry how to display message in app if device got no internet connection?

    - by Johannes
    Hello I've just started with programming for the Blackberry device. I'm using version 5 of the API. I'm building a very simple application which is just a browserfield. So far it's all working great. I can display my browserfield with the content I need. The problem I'm having now is if the device doesn't have an active internet connection I get the ugly "Error requesting content for" message. I would need to someone display my own message if the device doesn't have an active connection. Something like "You need to have an active internet connection to use this application" with an Exit button which closes the app. I've tried to find this for hours but no luck. Hopefully it's something relatively easy so I can get help here. Here's my code so far: package com.mycompany.webview; import net.rim.device.api.browser.field2.*; import net.rim.device.api.ui.*; import net.rim.device.api.ui.container.*; public class webview extends UiApplication { public static void main(String[] args) { webview app = new webview(); app.enterEventDispatcher(); } public webview() { pushScreen(new webviewScreen()); } } class webviewScreen extends MainScreen { public webviewScreen() { BrowserField myBrowserField = new BrowserField(); add(myBrowserField); myBrowserField.requestContent("http://www.google.com"); } } Would really appreciate some help please. Thanks

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