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• What parallel programming model do you recommend today to take advantage of the manycore processors

  - by Doctor J

  If you were writing a new application from scratch today, and wanted it to scale to all the cores you could throw at it tomorrow, what parallel programming model/system/language/library would you choose? Why? I am particularly interested in answers along these axes: Programmer productivity / ease of use (can mortals successfully use it?) Target application domain (what problems is it (not) good at?) Concurrency style (does it support tasks, pipelines, data parallelism, messages...?) Maintainability / future-proofing (will anybody still be using it in 20 years?) Performance (how does it scale on what kinds of hardware?) I am being deliberately vauge on the nature of the application in anticipation of getting good general answers useful for a variety of applications.

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• How to add response headers based on Content-type, or getting Content-type before the response is co

  - by Bozho

  I want to set the Expires header for all image/* and text/css. I'm doing this in a Filter. However: before calling chain.doFilter(..) the Content-type is not yet "realized" after calling chain.doFilter(..) the Content-type is set, but so is content-length, which forbids adding new headers (at least in Tomcat implementation) I can use the extensions of the requested resource, but since some of the css files are generated by richfaces by taking them from inside jar-files, the name of the file isn't x.css, but is /xx/yy/zz.xcss/DATB/.... So, is there a way to get the Content-type before the response is committed.

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• How can I implement incremental (find-as-you-type) search on command line?

  - by florianbw

  I'd like to write small scripts which feature incremental search (find-as-you-type) on the command line. Use case: I have my mobile phone connected via USB, Using gammu --sendsms TEXT I can write text messages. I have the phonebook as CSV, and want to search-as-i-type on that. What's the easiest/best way to do it? It might be in bash/zsh/Perl/Python or any other scripting language. Edit: Solution: Modifying Term::Complete (http://search.cpan.org/~jesse/perl-5.12.0/lib/Term/Complete.pm) did what I want. See below for the answer.

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• How to find control points for a BezierSegment given Start, End, and 2 Intersection Pts in C# - AKA

  - by softwarequestioneer

  Hi, I've been struggling looking for an understandable way to do this. I have four points, a StartPt, EndPoint, and Intersection points to represent the peak and valley in the bezier. The BezierSegment in C# requires start, controlPoint 1, controlPoint 2, endpoint - however I don't have any control points I only have these two points that lie along the bezier curves (i'm calling them intersection points above)... how can I calculate the two control points? Thanks in advance, this has been driving me crazy. There's some kind of explanation here: http://www.tinaja.com/glib/nubz4pts1.pdf but it's written in postscript and that language makes no sense to me at all - it's over my head.

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• Type problem when including tuple

  - by Person

  I'm using Visual Studio 2008 with Feature Pack 1. I have a typedef like this typedef std::tr1::tuple<std::string, std::string, int> tileInfo with a function like this const tileInfo& GetTile( int x, int y ) const. In the implementation file the function has the exact same signature (with the added class name qualifier) and I am getting a redefinition: different type modifiers error. It seems to be looking for an int& instead of a tileInfo& When I mouse over the type of the function in the header, i.e. tileInfo& it brings up a little bar saying static const int tileInfo. I think this may be the problem, but I'm not sure what to do. Any help is appreciated, thanks.

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• PostgreSQL: keep a certain number of records in a table

  - by Alexander Farber

  Hello, I have an SQL-table holding the last hands received by a player in card game. The hand is represented by an integer (32 bits == 32 cards): create table pref_hand ( id varchar(32) references pref_users, hand integer not NULL check (hand > 0), stamp timestamp default current_timestamp ); As the players are playing constantly and that data isn't important (just a gimmick to be displayed at player profile pages) and I don't want my database to grow too quickly, I'd like to keep only up to 10 records per player id. So I'm trying to declare this PL/PgSQL procedure: create or replace function pref_update_game(_id varchar, _hand integer) returns void as $BODY$ begin delete from pref_hand offset 10 where id=_id order by stamp; insert into pref_hand (id, hand) values (_id, _hand); end; $BODY$ language plpgsql; but unfortunately this fails with: ERROR: syntax error at or near "offset" because delete doesn't support offset. Does anybody please have a better idea here? Thank you! Alex

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• Shallow Copy in Java

  - by Vilius

  Hello there! I already know, what a shallow copy is, but I'm not able to impliment it. Here's a short example. public class Shallow { String name; int number; public Shallow (String name, int number) { this.name = name; this.number = number; } } Test the implementation ... public class ShallowTest { public static void main (String[] args) { Shallow shallow = new Shallow("Shallow", 123); Shallow shallowClone = new Shallow(shallow); shallowClone.name = 'Peter'; shallowClone.number = 321; System.out.println(shallow.name + " - " + shallow.number); } } As I purpose, just the reference of the non primitive datatype String would be copied, so that by calling "shallowClone.name = 'Peter';" I would also change the name of "shallow". Am I right? But somehow, it just does not want to work ....

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• Which SOA architecture is most appropriate for a Java application?

  - by Robert Greiner

  I am currently working on a pretty large Java 6 application where we are looking to split some of our functionality out into a service oriented architecture. It seems that the primary SOA framework for the application space is OSGi and I have been looking into Felix and Knopplerfish but I wanted to make sure that this isn't my only option. Does it make sense to use an actual web service protocol for our application like SOAP, even though we are not building a web app? Is this even acceptable? Have any of you used an implementation of OSGi (Felix, etc.) with your desktop application? if so, how did it go? Do you know of anything better? We're all pretty new to SOA here so any help would be greatly appreciated.

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• c99 goto past initialization

  - by R Samuel Klatchko

  While debugging a crash, I came across this issue in some code: int func() { char *p1 = malloc(...); if (p1 == NULL) goto err_exit; char *p2 = malloc(...); if (p2 == NULL) goto err_exit; ... err_exit: free(p2); free(p1); return -1; } The problem occurs when the first malloc fails. Because we jump across the initialization of p2, it contains random data and the call to free(p2) can crash. I would expect/hope that this would be treated the same way as in C++ where the compiler does not allow a goto to jump across an initialization. My question: is jumping across an initialization allowed by the standard or is this a bug in gcc's implementation of c99?

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• GUI Control For Audio Presentation

  - by Boris

  I need GUI control for audio file presentation. The language is not very important but it should run on windows platform. I should be able to :- load the file play the sound put and move markers across the audio bar. it would be nice if it can load itself from RTP wireshark captures (and not wav files). An example may be seen in audacity (may be someone even had an experience extracting it from there). Writing nyquist scripts in audacity is not a good option because I have to operate on RTP captures and not on raw sound samples. Another example of such control is wireshark RTP analyzer. Any advise?

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• Integrating WebSockets with Rails using Rack and Event Machine

  - by Toby Hede

  I have created an Asynchronous version of Rails 3 that I would like to integrate with a WebSocket implementation. I am using EventMachine, Ruby 1.9, Fibers and various em-flavoured libraries as documented by the wickedly good Ilya Grigorik. I have been looking at em-websocket as the handler for WebSocket connections but unsure of the best approach for hooking this into a Rails app. Ideally, this would work in a similar fashion to node.js with Express and Socket.io - incoming connections should be detected and dispatched to the WebSocket handler or the regular rails stack as indicated by the HTTP headers & etc. TL;DR WebSocket handler that plugs into an existing Rails application Transparently dispatch incoming WebSocket requests to endpoints in the app

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• How to implement cancellable worker thread

  - by Arnold Zokas

  Hi, I'm trying to implement a cancellable worker thread using the new threading constructs in System.Threading.Tasks namespace. So far I have have come up with this implementation: public sealed class Scheduler { private CancellationTokenSource _cancellationTokenSource; public System.Threading.Tasks.Task Worker { get; private set; } public void Start() { _cancellationTokenSource = new CancellationTokenSource(); Worker = System.Threading.Tasks.Task.Factory.StartNew( () => RunTasks(_cancellationTokenSource.Token), _cancellationTokenSource.Token ); } private static void RunTasks(CancellationToken cancellationToken) { while (!cancellationToken.IsCancellationRequested) { Thread.Sleep(1000); // simulate work } } public void Stop() { try { _cancellationTokenSource.Cancel(); Worker.Wait(_cancellationTokenSource.Token); } catch (OperationCanceledException) { // OperationCanceledException is expected when a Task is cancelled. } } } When Stop() returns I expect Worker.Status to be TaskStatus.Canceled. My unit tests have shown that under certain conditions Worker.Status remains set to TaskStatus.Running. Is this a correct way to implement a cancellable worker thread?

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• Find all paths from root to leaves of tree in Scheme

  - by grifaton

  Given a tree, I want to find the paths from the root to each leaf. So, for this tree: D / B / \ A E \ C-F-G has the following paths from root (A) to leaves (D, E, G): (A B D), (A B E), (A C F G) If I represent the tree above as (A (B D E) (C (F G))) then the function g does the trick: (define (g tree) (cond ((empty? tree) '()) ((pair? tree) (map (lambda (path) (if (pair? path) (cons (car tree) path) (cons (car tree) (list path)))) (map2 g (cdr tree)))) (else (list tree)))) (define (map2 fn lst) (if (empty? lst) '() (append (fn (car lst)) (map2 fn (cdr lst))))) But this looks all wrong. I've not had to do this kind of thinking for a while, but I feel there should be a neater way of doing it. Any ideas for a better solution (in any language) would be appreciated.

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• How to preserve object identity across different VMs

  - by wheleph

  To be specific let me illustrate the question with Spring http-remoting example. Suppose we have such implementation of a simple interface: public SearchServiceImpl implements SearchService { public SearchJdo processSearch(SearchJdo search) { search.name = "a funky name"; return search; } } SearchJdo is itself a simple POJO. Now when we call the method from a client through http-remoting we'll get: public class HTTPClient { public static void main(final String[] arguments) { final ApplicationContext context = new ClassPathXmlApplicationContext( "spring-http-client-config.xml"); final SearchService searchService = (SearchService) context.getBean("searchService"); SearchJdo search = new SearchJdo(); search.name = "myName"; // this method actually returns the same object it gets as an argument SearchJdo search2 = searchService.processSearch(search); System.out.println(search == search2); // prints "false" } } The problem is that the search objects are different because of serializaton although from logical prospective they are the same. The question is whether there are some technique that allows to support or emulate object identity across VMs.

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• How to join two wav file using python??

  - by kaushik

  I am using python programming language,I want to join to wav file one at the end of other wav file? I have a Question in the forum which suggest how to merge two wav file i.e add the contents of one wav file at certain offset,but i want to join two wav file at the end of each other... And also i had a prob playing the my own wav file,using winsound module..I was able to play the sound but using the time.sleep for certain time before playin any windows sound,disadvantage wit this is if i wanted to play a sound longer thn time.sleep(N),N sec also,the windows sound wil jst overlap after N sec play the winsound nd stop.. Can anyone help??please kindly suggest to how to solve these prob... Thanks in advance

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• problems with extended classes and overwrite with methods

  - by Marco

  I have a .net website written in C# and will make functionalities that other developers can use. So i will make some default implementation and a developer can overwrite some methods Example: i have a class ShoppingCart and a class Product the class product haves a method getProductPrice the shoppingcart will call the method getProductPrice for calculating the total price of cart The Shoppingcart and Product are in the same project and i will give the developers the .dll so they can't change the source code so we can update the assembly later So they need to make a other project and extend the product class and overwrite the method getProductPrice so they can implement there own logic The problem is that the shoppingcart will not call the extended method but the original If we make already a extended project for the developers and the shoppingcart will call the extended method then we have a circular reference because the extended product needs a reference to product and the shopping cart to the extended product partial classes also don't works because we only can use partials within the same assembly anyone a suggestion ? thanks in advance

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• Why does Java not have any destructor like C++?

  - by Abhishek Jain

  Java has its own garbage collection implementation so it does not require any destructor like C++ . This makes Java developer lazy in implementing memory management. And Garbage Collection is very expensive. Still we can have destructor along with garbage collector where developer can free resources and which can save garbage collector's work. This might improves the performance of application. Why does Java not provide any destructor kind of mechanism? Developer does not have control over GC but he/she can control or create object. Then why not give them ability to destruct the objects?

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• Why implement DB connection pointer object as a reference counting pointer? (C++)

  - by DVK

  At our company one of the core C++ classes (Database connection pointer) is implemented as a reference counting pointer. To be clear, the objects are NOT DB connections themselves, but pointers to a DB connection object. The library is very old, and nobody who designed is around anymore. So far, nether I, nor any C++ experts in the company that I asked have come up with a good reason for why this particular design was chosen. Any ideas? It is introducing some problems (partially due to awful reference pointer implementation used), and I'm trying to understand if this design actually has some deep underlying reasons? The usage pattern these days seems to be that the DB connection pointer object is returned by a DB connection manager class, and it's somewhat unclear whether DB connection pointers were designed to be able to be used independently of DB connection manager.

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• Why am I getting "Collection was modified; enumeration operation may not execute" when not modifying

  - by ccornet

  I have two collections of strings: CollectionA is a StringCollection property of an object stored in the system, while CollectionB is a List generated at runtime. CollectionA needs to be updated to match CollectionB if there are any differences. So I devised what I expected to be a simple LINQ method to perform the removal. var strDifferences = CollectionA.Where(foo => !CollectionB.Contains(foo)); foreach (var strVar in strDifferences) { CollectionA.Remove(strVar); } But I am getting a "Collection was modified; enumeration operation may not execute" error on strDifferences... even though it is a separate enumerable from the collection being modified! I originally devised this explicitly to evade this error, as my first implementation would produce it (as I was enumerating across CollectionA and just removing when !CollectionB.Contains(str)). Can anyone shed some insight into why this enumeration is failing?

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• Preventing EF4 ConstraintException when invoking TryUpdateModel

  - by twk

  Given following ASP.NET MVC controller code: [HttpPost] public ActionResult Create(FormCollection collection) { string[] whitelist = new []{ "CompanyName", "Address1", "Address2", ... }; Partner newPartner = new Partner(); if (TryUpdateModel(newPartner, whitelist, collection)) { var db = new mainEntities(); db.Partners.AddObject(newPartner); db.SaveChanges(); return RedirectToAction("Details/" + newPartner.ID); } else { return View(); } } The problem is with the Entity Framework 4: the example Partner entity is mapped to a database table with it's fields NOT ALLOWED to be NULL (which is ok by design - they're required). Unfortunately, invoking TryUpdateModel when some of the properties are nulls produces ConstraintException which is not expected! I do expect that TryUpdateModel return false in this case. It is ok that EF wouldn't allow set a property value to null if it should not be, but the TryUpdateMethod should handle that, and add the error to ModelState errors collection. I am wrong, or somebody screwed the implementation of TryUpdateModel method?

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• Is there any advantages to integrate Smarty with Zend?

  - by keisimone

  Hi, i am quite familiar with Smarty and recently decided to use Zend framework in implementation. because i am aware of the various advantages of Smarty, i insisted my contractor to integrate Smarty in. But now, i am questioning my assumptions. Should I integrate Smarty in with Zend framework? simply because I am familiar with Smarty syntax? I am also involved with the programming. I got the contractor to help in the architecture and with the prototype.

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• Would you use Code Bubbles?

  - by Paulo Santos

  I've read this question mentioning Code Bubbles and I've watched their video presentation. The video is impressive, and does seem a little bit futuristic, but apparently it's somewhat real. But that kept me thinking... Would a developer really use such tool? We, as developers, are used to deal with code files, organizing them in directories, in one way or another, some common IDE (for those language that has them). It would be a great leap to use something like Code Bubbles, as they propose. I, personally, am not sure if I could work in such environment... although I think I would just need some adjusting... but I really don't see my mind working out the kinks of it. What are your thoughts on this?

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• Documenting a policy based design

  - by academicRobot

  I'm re-working some prototype code into a policy based design in C++, and I'm wondering what the best practice is for documenting the design. My current plan is to document: Policy hierarchy Overview of each policy Description of each type/value/function in each policy I was thinking of putting this into a doxygen module, but this looks like it will be a bit awkward since formatting will have to be done by hand without code to base the doc on (that is, documenting the policies rather than the implementation of the policies). So my questions are: Are there other aspects of the design that should be documented? Are there any tricks to doing this efficiently in doxygen? Is there a tool other than doxygen thats better suited to this? What are some examples of well documented policy based design? This is my first serious attempt at policy based design. I think I have a working grasp of the principles, but whatever naivety I expose in this question is fair game for an answer too.

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• Why does Java force user-agent through simple Socket IO?

  - by Zombies

  I am using nothing but raw Socket IO. There isn't one HttpURLConnection nor any http client libs in my project. When I run it through wireshark I see somethign very revealing: GET / HTTP/1.1 User-Agent: Java/1.6.0_15 Host: www.google.com Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2 Connection: keep-alive Here is the crazy part, I never put ANY of that in my original request. My original request was: "GET http://www.google.com/ HTTP/1.1\r\n" + "Host: www.google.com\r\n" + "User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.8) Gecko/20100214 Ubuntu/9.10 (karmic) Firefox/3.5.8\r\n" + "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n" + "Accept-Language: en-us,en;q=0.5\r\n" + "Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\n" + "Keep-Alive: 300\r\n" + "\r\n"; I am using the default Sun JVM.

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• my first shader in WebGL

  - by Diego

  Hello, I am writing my first shader in WebGL. I was wondering if the GLSL language has any way to evaluate if an attribute or a uniform is null. According to the specs it does not support to do something like if (attributeX) { dothis(); } else{ dothat(): } And I think it would be a waste to write a bool attribute for each of these cases would be a waste. Another question: what happen during rendering when you don't pass along the uniforms or attribs to the shader? Thanks!

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