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  • QProcess, QEventLoop - of any use for parallel-processing

    - by dlib
    I wonder whether I could use QEventLoop (QProcess?) to parallelize multiple calls to same function with Qt. What is precisely the difference with QtConcurrent or QThread? What is a process and an event loop more precisely? I read that QCoreApplication must exec() as early as possible in main() method, so that I wonder why it is different from main Thread. could you point as some efficient reference to processes and thread with Qt? I came through the official doc and those things remain unclear. Thanks and regards.

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  • silverlight for .NET / CLR based numerical computing on osx

    - by Jonathan Shore
    I'm interested in using F# for numerical work, but my platforms are not windows based. Mono still has a significant performance penalty for programs that generate a significant amount of short-lived objects (as would be typical for functional languages). Silverlight is available on OSX. I had seen some reference indicating that assemblies compiled in the usual way could not be referenced, but not clear on the details. I'm not interested in UIs, but wondering whether could use the VM bundled with silverlight effectively for execution? I would want to be able to reference a large library of numerical models I already have in java (cross-compiled via IKVM to .NET assemblies) and a new codebase written in F#. My hope would be that the silverlight VM on OSX has good performance and can reference external assemblies and native libraries. Is this doable?

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  • Computing unique index for every poker starting hand

    - by Aly
    As there are 52 cards in a deck we know there are 52 choose 2 = 1326 distinct matchups, however in preflop poker this can be bucketed into 169 different hands such as AK offsuit and AK suited as whether it is A hearts K hearts or A spade K spades it makes no difference preflop. My question is, is there a nice mathematical property in which I can uniquely index each of these 169 hands (from 0 to 168 preferably). I am trying to create a look up table as a double[][] = new double [169][169] but have no way of changing a hand representation such as AKs (an Ace and a King of the same suit) to a unique index in this array.

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  • High CPU usage when running several "java -version" in parallel

    - by Prateesh
    This is just out of curiosity to understand i have a small shell script for ((i = 0; i < 50; i++)) do java -version & done when i run this my CPU usage report by sar is as below 07:51:25 PM CPU %user %nice %system %iowait %steal %idle 07:51:30 PM all 6.98 0.00 1.75 1.00 0.00 90.27 07:51:31 PM all 43.00 0.00 12.00 0.00 0.00 45.00 07:51:32 PM all 86.28 0.00 13.72 0.00 0.00 0.00 07:51:33 PM all 5.25 0.00 1.75 0.50 0.00 92.50 As you can see, on the third line the CPU is at 100% My java version is 1.5.0_22-b03.

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  • Unit testing with Mocks when SUT is leveraging Task Parallel Libaray

    - by StevenH
    I am trying to unit test / verify that a method is being called on a dependency, by the system under test. The depenedency is IFoo. The dependent class is IBar. IBar is implemented as Bar. Bar will call Start() on IFoo in a new (System.Threading.Tasks.)Task, when Start() is called on Bar instance. Unit Test (Moq): [Test] public void StartBar_ShouldCallStartOnAllFoo_WhenFoosExist() { //ARRANGE //Create a foo, and setup expectation var mockFoo0 = new Mock<IFoo>(); mockFoo0.Setup(foo => foo.Start()); var mockFoo1 = new Mock<IFoo>(); mockFoo1.Setup(foo => foo.Start()); //Add mockobjects to a collection var foos = new List<IFoo> { mockFoo0.Object, mockFoo1.Object }; IBar sutBar = new Bar(foos); //ACT sutBar.Start(); //Should call mockFoo.Start() //ASSERT mockFoo0.VerifyAll(); mockFoo1.VerifyAll(); } Implementation of IBar as Bar: class Bar : IBar { private IEnumerable<IFoo> Foos { get; set; } public Bar(IEnumerable<IFoo> foos) { Foos = foos; } public void Start() { foreach(var foo in Foos) { Task.Factory.StartNew( () => { foo.Start(); }); } } } I appears that the issue is obviously due to the fact that the call to "foo.Start()" is taking place on another thread (/task), and the mock (Moq framework) can't detect it. But I could be wrong. Thanks

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  • List of objects or parallel arrays of properties?

    - by Headcrab
    The question is, basically: what would be more preferable, both performance-wise and design-wise - to have a list of objects of a Python class or to have several lists of numerical properties? I am writing some sort of a scientific simulation which involves a rather large system of interacting particles. For simplicity, let's say we have a set of balls bouncing inside a box so each ball has a number of numerical properties, like x-y-z-coordinates, diameter, mass, velocity vector and so on. How to store the system better? Two major options I can think of are: to make a class "Ball" with those properties and some methods, then store a list of objects of the class, e. g. [b1, b2, b3, ...bn, ...], where for each bn we can access bn.x, bn.y, bn.mass and so on; to make an array of numbers for each property, then for each i-th "ball" we can access it's 'x' coordinate as xs[i], 'y' coordinate as ys[i], 'mass' as masses[i] and so on; To me it seems that the first option represents a better design. The second option looks somewhat uglier, but might be better in terms of performance, and it could be easier to use it with numpy and scipy, which I try to use as much as I can. I am still not sure if Python will be fast enough, so it may be necessary to rewrite it in C++ or something, after initial prototyping in Python. Would the choice of data representation be different for C/C++? What about a hybrid approach, e.g. Python with C++ extension?

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  • The speed of .NET in numerical computing

    - by Yin Zhu
    In my experience, .net is 2 to 3 times slower than native code. (I implemented L-BFGS for multivariate optimization). I have traced the ads on stackoverflow to http://www.centerspace.net/products/ the speed is really amazing, the speed is close to native code. How can they do that? They said that: Q. Is NMath "pure" .NET? A. The answer depends somewhat on your definition of "pure .NET". NMath is written in C#, plus a small Managed C++ layer. For better performance of basic linear algebra operations, however, NMath does rely on the native Intel Math Kernel Library (included with NMath). But there are no COM components, no DLLs--just .NET assemblies. Also, all memory allocated in the Managed C++ layer and used by native code is allocated from the managed heap. Can someone explain more to me? Thanks!

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  • Grails - Recursive computing call "StackOverflowError" and don't update on show

    - by Kedare
    Hello, I have a little problem, I have made a Category domain on Grails, but I want to "cache" the string representation on the database by generating it when the representation field is empty or NULL (to avoid recursive queries at each toString), here is the code : package devkedare class Category { String title; String description; String representation; Date dateCreated; Date lastUpdate; Category parent; static constraints = { title(blank:false, nullable:false, size:2..100); description(blank:true, nullable:false); dateCreated(nullable:true); lastUpdate(nullable:true); autoTimestamp: true; } static hasMany = [childs:Category] @Override String toString() { if((!this.representation) || (this.representation == "")) { this.computeRepresentation(true) } return this.representation; } String computeRepresentation(boolean updateChilds) { if(updateChilds) { for(child in this.childs) { child.representation = child.computeRepresentation(true); } } if(this.parent) { this.representation = "${this.parent.computeRepresentation(false)}/${this.title}"; } else { this.representation = this.title } return this.representation; } void beforeUpdate() { this.computeRepresentation(true); } } There is 2 problems : It don't update the representation when the representation if NULL or empty and toString id called, it only update it on save, how to fix that ? On some category, updating it throw a StackOverflowError, here is an example of my actual category table as CSV : Uploaded the csv file here, pasting csv looks buggy: http://kedare.free.fr/Dist/01.csv Updating the representation works everywhere except on "IT" that throw a StackOverlowError (this is the only category that has many childs). Any idea of how can I fix those 2 problems ? Thank you !

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  • IIS SMTP server (Installed on local server) in parallel to Google Apps

    - by sharru
    I am currently using free version of Google Apps for hosting my email.It works great for my official mails my email on Google is [email protected]. In addition I'm sending out high volume mails (registrations, forgotten passwords, newsletters etc) from the website (www.mydomain.com) using IIS SMTP installed on my windows machine. These emails are sent from [email protected] My problem is that when I send email from the website using IIS SMTP to a mail address [email protected] I don’t receive the email to Google apps. (I only receive these emails if I install a pop service on the server with the [email protected] email box). It seems that the IIS SMTP is ignoring the domain MX records and just delivers these emails to my local server. Here are my DNS records for domain.com: mydomain.com A 82.80.200.20 3600s mydomain.com TXT v=spf1 ip4: 82.80.200.20 a mx ptr include:aspmx.googlemail.com ~all mydomain.com MX preference: 10 exchange: aspmx2.googlemail.com 3600s mydomain.com MX preference: 10 exchange: aspmx3.googlemail.com 3600s mydomain.com MX preference: 10 exchange: aspmx4.googlemail.com 3600s mydomain.com MX preference: 10 exchange: aspmx5.googlemail.com 3600s mydomain.com MX preference: 1 exchange: aspmx.l.google.com 3600s mydomain.com MX preference: 5 exchange: alt1.aspmx.l.google.com 3600s mydomain.com MX preference: 5 exchange: alt2.aspmx.l.google.com 3600s Please help! Thanks.

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  • load multiple directions in parallel in google map

    - by Maneesh
    My aim is to get distance between many locations thru GDirection object. Since I am using multiple objects, am not able to get distnace. Can someone help me out. Below is the code. for(ct=0;ct<size;ct++) { var gd=new GDirections(); gd.load("from: " + address + " to: " + offaddress[ct]); GEvent.addListener(directions,"load", function() { sor[ct]= gd.getDistance().html; }

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  • Unable to make 2 parallel TCP requests to the same TCP Client

    - by soldieraman
    Error: Unable to read data from the transport connection: A blocking operation was interrupted by a call to WSACancelBlockingCall Situation There is a TCP Server My web application connects to this TCP Server Using the below code: TcpClientInfo = new TcpClient(); _result = TcpClientInfo.BeginConnect(<serverAddress>,<portNumber>, null, null); bool success = _result.AsyncWaitHandle.WaitOne(20000, true); if (!success) { TcpClientInfo.Close(); throw new Exception("Connection Timeout: Failed to establish connection."); } NetworkStreamInfo = TcpClientInfo.GetStream(); NetworkStreamInfo.ReadTimeout = 20000; 2 Users use the same application from two different location to access information from this server at the SAME TIME Server takes around 2sec to reply Both Connect But One of the user gets above error "Unable to read data from the transport connection: A blocking operation was interrupted by a call to WSACancelBlockingCall" when trying to read data from stream How can I resolve this issue? Use a better way of connecting to the server Can't because it's a server issue if a server issue, how should the server handle request to avoid this problem

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  • Existing LINQ extension method similar to Parallel.For?

    - by Joel Martinez
    The linq extension methods for ienumerable are very handy ... but not that useful if all you want to do is apply some computation to each item in the enumeration without returning anything. So I was wondering if perhaps I was just missing the right method, or if it truly doesn't exist as I'd rather use a built-in version if it's available ... but I haven't found one :-) I could have sworn there was a .ForEach method somewhere, but I have yet to find it. In the meantime, I did write my own version in case it's useful for anyone else: using System.Collections; using System.Collections.Generic; public delegate void Function<T>(T item); public delegate void Function(object item); public static class EnumerableExtensions { public static void For(this IEnumerable enumerable, Function func) { foreach (object item in enumerable) { func(item); } } public static void For<T>(this IEnumerable<T> enumerable, Function<T> func) { foreach (T item in enumerable) { func(item); } } } usage is: myEnumerable.For<MyClass>(delegate(MyClass item) { item.Count++; });

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  • Code computing the cross-product

    - by WizardOfOdds
    This is not a dupe of my question: http://stackoverflow.com/questions/2532810/detecting-one-points-location-compared-to-two-other-points If I have the following piece of pseudo-C/Java/C# code: int a[]= { 30, 20 }; int b[] = { 40, 50 }; int c[] = {12, 12}; How do I compute the sign of the cross-product ABxAC? I'm only interested in the sign, so I have: boolean signABxAC = ? Now concretely what do I write to get the sign of the cross-product ABxAC?

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  • operators computing direction

    - by amiad
    Hi all! I enqunterd something that I can't understand. I have this code: cout << "f1 * f1 + f2 * f1 - f1 / f2 is: "<< f1 * f1 + f2 * f1 - f1 / f2 << endl; All the "f"s are objects, and all the operators are overloaded. The weird this is that the first computarion is of the "/" operator, then the second "" and then the first "", after that - the operator "+" and at last - operator "-". So basicly - the "/" and "*" worked from right to left, and the "+" and "-" operators worked from left to right. I made another test... I checked this code: cout << "f1 * f1 / f2 is: " << f1 * f1 / f2 << endl; Now, the first operator was "*" and only then oerator "/". So now, it worked from left to right. Can someone help me underatand why is there diffrence in the directions? 10X!

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  • Computing "average" of two colors

    - by Francisco P.
    This is only marginally programming related - has much more to do w/ colors and their representation. I am working on a very low level app. I have an array of bytes in memory. Those are characters. They were rendered with anti-aliasing: they have values from 0 to 255, 0 being fully transparent and 255 totally opaque (alpha, if you wish). I am having trouble conceiving an algorithm for the rendering of this font. I'm doing the following for each pixel: // intensity is the weight I talked about: 0 to 255 intensity = glyphs[text[i]][x + GLYPH_WIDTH*y]; if (intensity == 255) continue; // Don't draw it, fully transparent else if (intensity == 0) setPixel(x + xi, y + yi, color, base); // Fully opaque, can draw original color else { // Here's the tricky part // Get the pixel in the destination for averaging purposes pixel = getPixel(x + xi, y + yi, base); // transfer is an int for calculations transfer = (int) ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.red + (float) pixel.red)/2); // This is my attempt at averaging newPixel.red = (Byte) transfer; transfer = (int) ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.green + (float) pixel.green)/2); newPixel.green = (Byte) transfer; // transfer = (int) ((float) ((float) 255.0 - (float) intensity)/255.0 * (((float) color.blue) + (float) pixel.blue)/2); transfer = (int) ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.blue + (float) pixel.blue)/2); newPixel.blue = (Byte) transfer; // Set the newpixel in the desired mem. position setPixel(x+xi, y+yi, newPixel, base); } The results, as you can see, are less than desirable. That is a very zoomed in image, at 1:1 scale it looks like the text has a green "aura". Any idea for how to properly compute this would be greatly appreciated. Thanks for your time!

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  • TeamCity run Nunit tests in Parallel

    - by Bob Sinclar
    So I was thinking that there must be a better way to run NUnit tests for a .net project via teamcity. Currently the build of the project takes about 10 minutes , and the testing step takes 30ish minutes. I was thinking about splitting up the Nunit tests into 3 groups, assigning them each to a different agent. And then make sure they have a build dependency on the initial build before they start. This was the best way i thought of doing it, Is there a different way I should also consider? On a side note Is it possible to combine all the Nunit tests at the end to get one report from the tests being build on 3 different machines? I dont think this is possible unless someone thought of a clever hack.

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  • Parallel Task In C#.net

    - by Test123
    I have C#.net application. I wanted to run my application In Thread. But because of third party dll it dont allow to use application in multiThread. There is one object in thrid party dll ,which only allow to create instance at one time only. When i manually run application exe instnace multiple time & process my data it process successfully..(might because of each exe run with its application domain) Same thing i require to implement from C# code. for that i have created dll which can accessible by Type.GetTypeFromProgID()..but multiple dll instnace creating same problem. Is there any way i could achive manual parallelism through code to process same exe code in multiple application domain?

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  • Arrays/Lists and computing hashvalues (VB, C#)

    - by Jeffrey Kern
    I feel bad asking this question but I am currently not able to program and test this as I'm writing this on my cell-phone and not on my dev machine :P (Easy rep points if someone answers! XD ) Anyway, I've had experience with using hashvalues from String objects. E.g., if I have StringA and StringB both equal to "foo", they'll both compute out the same hashvalue, because they're set to equal values. Now what if I have a List, with T being a native data type. If I tried to compute the hashvalue of ListA and ListB, assuming that they'd both be the same size and contain the same information, wouldn't they have equal hashvalues as well? Assuming as sample dataset of 'byte' with a length of 5 {5,2,0,1,3}

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  • C#: Parallel forms, multithreading and "applications in application"

    - by Harry
    First, what I need is - n WebBrowser-s, each in its own window doing its own job. The user should be able to see them all, or just one of them (or none), and to execute commands on each one. There is a main form, without a browser, this one contains control panel for my application. The key feautre is, each browser logs on to secured web page and it needs to stay logged in as long as possible. Well, I've done it, but I'm afraid something is wrong with my approach. The question is: Is code below valid, or rather a nasty hack which can cause problems: internal class SessionList : List<Session> { public SessionList(Server main) { MyRecords.ForEach(record => { var st = new System.Threading.Thread((data) => { var s = new Session(main, data as MyRecord); this.Add(s); Application.Run(s); Application.ExitThread(); }); st.SetApartmentState(System.Threading.ApartmentState.STA); st.Start(record); }); } // some other uninteresting methods here... } What's going on here? Session inherits from Form, so it creates a form, puts WebBrowser into it, and has methods to operate on websites. WebBrowser requires to be run in STA thread, so we provide one for each browser. The most interesting part of it is Application.Run(s). It makes the newly created forms alive and interactive. The next Application.ExitThread() is called after browser window is closed and its controls disposed. Main application stays alive to perform the rest of the cleanup job. When user select "Exit" or "Shutdown" option - first the browser threads are ended, so Application.ExitThread() is called. It all works, but everywhere I can read about "main GUI thread" - and here - I've created many GUI threads. I handle communication between main form and my new forms (sessions) with thread-safe methods using Invoke(). It all works, so is it right or is it wrong? Is everything right with using Application.Run() more than once in one application? :) An ugly hack or a normal practice? This code dies if I start a WebBrowser from the session form thread. It beats me why. It works however if I start WebBrowser (by changing its Url property) from any other thread. I'd like to know more what is really happening in such application. But most of all - I'd like to know if my idea of "applications in application" is OK. I'm not sure what exactly does Application.Run() do. Without it forms created in new threads were dead unresponsive. How is it possible I can call Application.Run() many times? It seems to do exactly what it should, but it seems a little undocumented feature to me. I'm almost sure, that the crashes are caused by WebBrowser component itself (since it's not completely "managed" and "native"). But maybe it's something else.

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  • Whats the most common waste of computing power in javascipt

    - by qwertymk
    We've all seen people who do this jQuery('a').each(function(){ jQuery(this)[0].innerHTML += ' proccessed'; }); function letsPoluteNS() { polute = ''; for (morePolution = 0; morePolution < arguments.length; morePolution++) polute.join(arguments[morePolution]); return polute; } and so on. I was wondering what people have seen the most common javascript/jQuery technique that is slowing down the page and/or wasting time for the javascript engine. PS I know that this question may not seem to fit into whats an accepted question, yet I'm asking for what the most common accepted waste is

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  • Native arrays and computing hashvalues (VB, C#)

    - by Jeffrey Kern
    I feel bad asking this question but I am currently not able to program and test this as I'm writing this on my cell-phone and not on my dev machine :P (Easy rep points if someone answers! XD ) Anyway, I've had experience with using hashvalues from String objects. E.g., if I have StringA and StringB both equal to "foo", they'll both compute out the same hashvalue, because they're set to equal values. Now what if I have a List, with T being a native data type. If I tried to compute the hashvalue of ListA and ListB, assuming that they'd both be the same size and contain the same information, wouldn't they have equal hashvalues as well?

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  • How to Design Programs: An Introduction to Programming and Computing -- teacher guide access

    - by user295683
    Hello -- I'm a biologist switching careers, and trying to learn programming as a result. I stumbled upon the aforementioned book on Amazon, which jived with my liberal arts background. Despite my great satisfaction with the didactic approach, I was frustrated to see that the answers to the exercises are restricted to teachers only. As I am pursuing this endeavor on my own, this restriction dramatically cripples the value of this book. My request to the author's website for access to the answers has not been answered, and I would desperately like to continue with this book. Anyone have any experience dealing with the book's website, or at the very least a torrent of the answers? Otherwise, I suspect I will be relegated to using JavaScript for everything! Thanks!

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  • Computing, storing, and retrieving values to and from an N-Dimensional matrix

    - by Adam S
    This question is probably quite different from what you are used to reading here - I hope it can provide a fun challenge. Essentially I have an algorithm that uses 5(or more) variables to compute a single value, called outcome. Now I have to implement this algorithm on an embedded device which has no memory limitations, but has very harsh processing constraints. Because of this, I would like to run a calculation engine which computes outcome for, say, 20 different values of each variable and stores this information in a file. You may think of this as a 5(or more)-dimensional matrix or 5(or more)-dimensional array, each dimension being 20 entries long. In any modern language, filling this array is as simple as having 5(or more) nested for loops. The tricky part is that I need to dump these values into a file that can then be placed onto the embedded device so that the device can use it as a lookup table. The questions now, are: What format(s) might be acceptable for storing the data? What programs (MATLAB, C#, etc) might be best suited to compute the data? C# must be used to import the data on the device - is this possible given your answer to #1?

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