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  • Are C++ meta-templates required knowledge for programmers?

    - by Robert Gould
    In my experience Meta-templates are really fun (when your compilers are compliant), and can give good performance boosts, and luckily I'm surrounded by seasoned C++ programmers that also grok meta-templates, however occasionally a new developer arrives and can't make heads or tails of some of the meta-template tricks we use (mostly Andrei Alenxandrescu stuff), for a few weeks until he gets initiated appropriately. So I was wondering what's the situation for other C++ programmers out there? Should meta-template programming be something C++ programmers should be "required" to know (excluding entry level students of course), or not? Edit: Note my question is related to production code and not little samples or prototypes

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  • Is it a good idea to create an STL iterator which is noncopyable?

    - by BillyONeal
    Most of the time, STL iterators are CopyConstructable, because several STL algorithms require this to improve performance, such as std::sort. However, I've been working on a pet project to wrap the FindXFile API (previously asked about), but the problem is it's impossible to implement a copyable iterator around this API. A find handle cannot be duplicated by any means -- DuplicateHandle specifically forbids passing handles to it. And if you just maintain a reference count to the find handle, then a single increment by any copy results in an increment of all copies -- clearly that is not what a copy constructed iterator is supposed to do. Since I can't satisfy the traditional copy constructible requirement for iterators here, is it even worth trying to create an "STL style" iterator? On one hand, creating some other enumeration method is going to not fall into normal STL conventions, but on the other, following STL conventions are going to confuse users of this iterator if they try to CopyConstruct it later. Which is the lesser of two evils?

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  • Multiple ParticleSystems in cocos2d

    - by Mattias Akerman
    I wonder about what road I should go with ParticleSystem. In this particular case I want to create 1-20 small explosions at the same time but with different positions. Right now I'm creating a new ParticleSystem for each explosion and then release it, but of course this is very punishing to the performance. My question is: Is there a way to create one ParticleSystem with multiple emitting sources. If not should I create an array of ParticleSystem in init and then use a free one when an explosion is needed? Or is there another approach I haven't thought of?

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  • Struct in C, are they efficient?

    - by pygabriel
    I'm reading some C code like that: double function( int lena,double xa,double ya, double za, double *acoefs, ..., int lenb,double xb,double yb, double zb, double *bcoefs, ..., same for c, same for d ) This function is called in the code mor than 100.000 times so it's performance-critical. I'm trying to extend this code but I want to know if it's efficient or not (and how much this influences the speed) to encapsulate all the parameters in a struct like this struct PGTO { int len; double x,y,z ; double *acoefs } and then access the parameters in the function.

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  • Hudson trigget builds remotely gives a forbidden 403 error

    - by Ritesh M Nayak
    I have a shell script on the same machine that hudson is deployed on and upon executing it, it calls wget on a hudson build trigger URL. Since its the same machine, I access it as http://localhost:8080/hudson/job/jobname/build?token=sometoken Typically, this is supposed to trigger a build on the project. But I get a 403 forbidden when I do this. Anybody has any idea why? I have tried this using a browser and it triggers the build, but via the command line it doesn't seem to work. Any ideas?

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  • Need details about applications that are running on Windows Azure

    - by veda
    I have an application which requires large amount of data storage (say some PB) and computing resources. Instead of going for clusters, I am planning to propose to use Windows Azure Cloud for this application. I have gone through white papers of Windows Azure and have collected some details about Azure. But I feel that is not substantial. I need to do some case study about applications that are running on the azure and that uses azure storage efficiently. I looked for several research paper in related to performance of the applications in Windows Azure. But as Azure was quite new, I wasn't able to find any. Now, I am looking for some white papers/details regarding application that uses azure storage to substantiate my proposal. I also need to understand the windows azure storage architecture and virtual machine architecture. Do anyone know some research papers or details or blogs or something related to these topics.

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  • Make MySQL database replication always use the most free node?

    - by Chad Johnson
    We started using Multi-Master Replication Manager for MySQL, and I am wondering whether it is possible to to treat this setup like multi-symmetric processing: a process pops off the process queue, and the node (in this case a server) that is most free is selected for the job. It seems that what happens is, the service switches to a slave ONLY when it mysqld crashes or goes away. Is there a way to make database replication for MySQL act in more of a distributed manner? Maybe there is other software besides MMM that can do this? Is there a way to switch the reader role to another server whene mysqld slows down (rather than just when it fails)?

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  • PostgreSQL 8.3 data types: xml vs varchar

    - by Sejanus
    There's xml data type in Postgres, I never used it before so I'd like to hear opinions. Downsides and upsides vs using regular varchar (or Text) column to store xml. The text I'm going to store is xml, well-formed, UTF-8. No need to search by it (I've read searching by xml is slow). This XML actually is data prepared for PDF generation with Apache FOP. XML can be generated dynamically from data found elsewhere (other Postgres tables), it's stored as is only so that I won't need to generate it twice. Kinda backup#2 for already generated PDF documents. Anything else to know? Good practices, performance, maintenance, etc?

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  • Why my application ask for a codec to pla the MVI(.MOV) video files while i can play them on WMP and QuickTime?

    - by Daniel Lip
    I have an application i did some time ago when im loading the video file its ok when trying to play/use the file im getting the messageBox message say that its need a codec to use gspot or search the internet. Wehn im playing this files on my hard disk with Windows Media Play or either QuickTime there is no problems. The Video files for example name are: MVI_2483 in the file name properties i see its type: Quick Time Movie (.MOV) In my application im using DirectShowLib-2005.dll this is the class im using in my case to extract the video file im using it in my application to extract only lightnings from the video file name. In Form1 i have a button click event that just starting the action: private void button8_Click(object sender, EventArgs e) { viewToolStripMenuItem.Enabled = false; fileToolStripMenuItem.Enabled = false; button2.Enabled = false; label14.Visible = false; label15.Visible = false; label21.Visible = false; label22.Visible = false; label24.Visible = false; label25.Visible = false; ExtractAutomatic = true; DirectoryInfo info = new DirectoryInfo(_videoFile); string dirName = info.Name; automaticModeDirectory = dirName + "_Automatic"; subDirectoryName = _outputDir + "\\" + automaticModeDirectory; if (secondPass == true) { Start(true); } Start(false); } This is the function start in Form1: private void Start(bool secondpass) { setpicture(-1); if (Directory.Exists(_outputDir) && secondpass == false) { } else { Directory.CreateDirectory(_outputDir); } if (ExtractAutomatic == true) { string subDirectory_Automatic_Name = _outputDir + "\\" + automaticModeDirectory; Directory.CreateDirectory(subDirectory_Automatic_Name); f = new WmvAdapter(_videoFile, Path.Combine(subDirectory_Automatic_Name)); } else { string subDirectory_Manual_Name; if (Directory.Exists(subDirectoryName)) { subDirectory_Manual_Name = subDirectoryName; f = new WmvAdapter(_videoFile, Path.Combine(subDirectory_Manual_Name)); } else { subDirectory_Manual_Name = _outputDir + "\\" + averagesListTextFileDirectory + "_Manual"; Directory.CreateDirectory(subDirectory_Manual_Name); f = new WmvAdapter(_videoFile, Path.Combine(subDirectory_Manual_Name)); } } button1.Enabled = false; f.Secondpass = secondpass; f.FramesToSave = _fts; f.FrameCountAvailable += new WmvAdapter.FrameCountEventHandler(f_FrameCountAvailable); f.StatusChanged += new WmvAdapter.EventHandler(f_StatusChanged); f.ProgressChanged += new WmvAdapter.ProgressEventHandler(f_ProgressChanged); this.Text = "Processing Please Wait..."; label5.ForeColor = Color.Green; label5.Text = "Processing Please Wait"; button8.Enabled = false; button5.Enabled = false; label5.Visible = true; pictureBox1.Image = Lightnings_Extractor.Properties.Resources.Weather_Michmoret; Hrs = 0; //number of hours Min = 0; //number of Minutes Sec = 0; //number of Sec timeElapsed = 0; label10.Text = "00:00:00"; label11.Visible = false; label12.Visible = false; label9.Visible = false; label8.Visible = false; this.button1.Enabled = false; myTrackPanelss1.trackBar1.Enabled = false; this.checkBox2.Enabled = false; this.checkBox1.Enabled = false; numericUpDown1.Enabled = false; timer1.Start(); label2.Text = ""; label1.Visible = true; label2.Visible = true; label3.Visible = true; label4.Visible = true; f.Start(); } And this is the class wich is not my oqn class i just just defined it in some places wich making the problem: using System; using System.Diagnostics; using System.Drawing; using System.Drawing.Imaging; using System.IO; using System.Runtime.InteropServices; using DirectShowLib; using System.Collections.Generic; using Extracting_Frames; using System.Windows.Forms; namespace Polkan.DataSource { internal class WmvAdapter : ISampleGrabberCB, IDisposable { #region Fields_Properties_and_Events bool dis = false; int count = 0; const string fileName = @"d:\histogramValues.dat"; private IFilterGraph2 _filterGraph; private IMediaControl _mediaCtrl; private IMediaEvent _mediaEvent; private int _width; private int _height; private readonly string _outFolder; private int _frameId; //better use a custom EventHandler that passes the results of the action to the subscriber. public delegate void EventHandler(object sender, EventArgs e); public event EventHandler StatusChanged; public delegate void FrameCountEventHandler(object sender, FrameCountEventArgs e); public event FrameCountEventHandler FrameCountAvailable; public delegate void ProgressEventHandler(object sender, ProgressEventArgs e); public event ProgressEventHandler ProgressChanged; private IMediaSeeking _mSeek; private long _duration = 0; private long _avgFrameTime = 0; //just save the averages to a List (not to fs) public List<double> AveragesList { get; set; } public List<long> histogramValuesList; public bool Secondpass { get; set; } public List<int> FramesToSave { get; set; } #endregion #region Constructors and Destructors public WmvAdapter(string file, string outFolder) { _outFolder = outFolder; try { SetupGraph(file); } catch { Dispose(); MessageBox.Show("A codec is required to load this video file. Please use http://www.headbands.com/gspot/ or search the web for the correct codec"); } } ~WmvAdapter() { CloseInterfaces(); } #endregion public void Dispose() { CloseInterfaces(); } public void Start() { EstimateFrameCount(); int hr = _mediaCtrl.Run(); WaitUntilDone(); DsError.ThrowExceptionForHR(hr); } public void WaitUntilDone() { int hr; const int eAbort = unchecked((int)0x80004004); do { System.Windows.Forms.Application.DoEvents(); EventCode evCode; if (dis == true) { return; } hr = _mediaEvent.WaitForCompletion(100, out evCode); }while (hr == eAbort); DsError.ThrowExceptionForHR(hr); OnStatusChanged(); } //Edit: added events protected virtual void OnStatusChanged() { if (StatusChanged != null) StatusChanged(this, new EventArgs()); } protected virtual void OnFrameCountAvailable(long frameCount) { if (FrameCountAvailable != null) FrameCountAvailable(this, new FrameCountEventArgs() { FrameCount = frameCount }); } protected virtual void OnProgressChanged(int frameID) { if (ProgressChanged != null) ProgressChanged(this, new ProgressEventArgs() { FrameID = frameID }); } /// <summary> build the capture graph for grabber. </summary> private void SetupGraph(string file) { ISampleGrabber sampGrabber = null; IBaseFilter capFilter = null; IBaseFilter nullrenderer = null; _filterGraph = (IFilterGraph2)new FilterGraph(); _mediaCtrl = (IMediaControl)_filterGraph; _mediaEvent = (IMediaEvent)_filterGraph; _mSeek = (IMediaSeeking)_filterGraph; var mediaFilt = (IMediaFilter)_filterGraph; try { // Add the video source int hr = _filterGraph.AddSourceFilter(file, "Ds.NET FileFilter", out capFilter); DsError.ThrowExceptionForHR(hr); // Get the SampleGrabber interface sampGrabber = new SampleGrabber() as ISampleGrabber; var baseGrabFlt = sampGrabber as IBaseFilter; ConfigureSampleGrabber(sampGrabber); // Add the frame grabber to the graph hr = _filterGraph.AddFilter(baseGrabFlt, "Ds.NET Grabber"); DsError.ThrowExceptionForHR(hr); // --------------------------------- // Connect the file filter to the sample grabber // Hopefully this will be the video pin, we could check by reading it's mediatype IPin iPinOut = DsFindPin.ByDirection(capFilter, PinDirection.Output, 0); // Get the input pin from the sample grabber IPin iPinIn = DsFindPin.ByDirection(baseGrabFlt, PinDirection.Input, 0); hr = _filterGraph.Connect(iPinOut, iPinIn); DsError.ThrowExceptionForHR(hr); // Add the null renderer to the graph nullrenderer = new NullRenderer() as IBaseFilter; hr = _filterGraph.AddFilter(nullrenderer, "Null renderer"); DsError.ThrowExceptionForHR(hr); // --------------------------------- // Connect the sample grabber to the null renderer iPinOut = DsFindPin.ByDirection(baseGrabFlt, PinDirection.Output, 0); iPinIn = DsFindPin.ByDirection(nullrenderer, PinDirection.Input, 0); hr = _filterGraph.Connect(iPinOut, iPinIn); DsError.ThrowExceptionForHR(hr); // Turn off the clock. This causes the frames to be sent // thru the graph as fast as possible hr = mediaFilt.SetSyncSource(null); DsError.ThrowExceptionForHR(hr); // Read and cache the image sizes SaveSizeInfo(sampGrabber); //Edit: get the duration hr = _mSeek.GetDuration(out _duration); DsError.ThrowExceptionForHR(hr); } finally { if (capFilter != null) { Marshal.ReleaseComObject(capFilter); } if (sampGrabber != null) { Marshal.ReleaseComObject(sampGrabber); } if (nullrenderer != null) { Marshal.ReleaseComObject(nullrenderer); } GC.Collect(); } } private void EstimateFrameCount() { try { //1sec / averageFrameTime double fr = 10000000.0 / _avgFrameTime; double frameCount = fr * (_duration / 10000000.0); OnFrameCountAvailable((long)frameCount); } catch { } } public double framesCounts() { double fr = 10000000.0 / _avgFrameTime; double frameCount = fr * (_duration / 10000000.0); return frameCount; } private void SaveSizeInfo(ISampleGrabber sampGrabber) { // Get the media type from the SampleGrabber var media = new AMMediaType(); int hr = sampGrabber.GetConnectedMediaType(media); DsError.ThrowExceptionForHR(hr); if ((media.formatType != FormatType.VideoInfo) || (media.formatPtr == IntPtr.Zero)) { throw new NotSupportedException("Unknown Grabber Media Format"); } // Grab the size info var videoInfoHeader = (VideoInfoHeader)Marshal.PtrToStructure(media.formatPtr, typeof(VideoInfoHeader)); _width = videoInfoHeader.BmiHeader.Width; _height = videoInfoHeader.BmiHeader.Height; //Edit: get framerate _avgFrameTime = videoInfoHeader.AvgTimePerFrame; DsUtils.FreeAMMediaType(media); GC.Collect(); } private void ConfigureSampleGrabber(ISampleGrabber sampGrabber) { var media = new AMMediaType { majorType = MediaType.Video, subType = MediaSubType.RGB24, formatType = FormatType.VideoInfo }; int hr = sampGrabber.SetMediaType(media); DsError.ThrowExceptionForHR(hr); DsUtils.FreeAMMediaType(media); GC.Collect(); hr = sampGrabber.SetCallback(this, 1); DsError.ThrowExceptionForHR(hr); } private void CloseInterfaces() { try { if (_mediaCtrl != null) { _mediaCtrl.Stop(); _mediaCtrl = null; dis = true; } } catch (Exception ex) { Debug.WriteLine(ex); } if (_filterGraph != null) { Marshal.ReleaseComObject(_filterGraph); _filterGraph = null; } GC.Collect(); } int ISampleGrabberCB.SampleCB(double sampleTime, IMediaSample pSample) { Marshal.ReleaseComObject(pSample); return 0; } int ISampleGrabberCB.BufferCB(double sampleTime, IntPtr pBuffer, int bufferLen) { if (Form1.ExtractAutomatic == true) { using (var bitmap = new Bitmap(_width, _height, _width * 3, PixelFormat.Format24bppRgb, pBuffer)) { if (!this.Secondpass) { long[] HistogramValues = Form1.GetHistogram(bitmap); long t = Form1.GetTopLumAmount(HistogramValues, 1000); Form1.averagesTest.Add(t); } else { //this is the changed part if (_frameId > 0) { if (Form1.averagesTest[_frameId] / 1000.0 - Form1.averagesTest[_frameId - 1] / 1000.0 > 150.0) { count = 6; } if (count > 0) { bitmap.RotateFlip(RotateFlipType.Rotate180FlipX); bitmap.Save(Path.Combine(_outFolder, _frameId.ToString("D6") + ".bmp")); count --; } } } _frameId++; //let only report each 100 frames for performance if (_frameId % 100 == 0) OnProgressChanged(_frameId); } } else { using (var bitmap = new Bitmap(_width, _height, _width * 3, PixelFormat.Format24bppRgb, pBuffer)) { if (!this.Secondpass) { //get avg double average = GetAveragePixelValue(bitmap); if (AveragesList == null) AveragesList = new List<double>(); //save avg AveragesList.Add(average); //***************************\\ // for (int i = 0; i < (int)framesCounts(); i++) // { // get histogram values long[] HistogramValues = Form1.GetHistogram(bitmap); if (histogramValuesList == null) histogramValuesList = new List<long>(256); histogramValuesList.AddRange(HistogramValues); //***************************\\ //} } else { if (FramesToSave != null && FramesToSave.Contains(_frameId)) { bitmap.RotateFlip(RotateFlipType.Rotate180FlipX); bitmap.Save(Path.Combine(_outFolder, _frameId.ToString("D6") + ".bmp")); // get histogram values long[] HistogramValues = Form1.GetHistogram(bitmap); if (histogramValuesList == null) histogramValuesList = new List<long>(256); histogramValuesList.AddRange(HistogramValues); using (BinaryWriter binWriter = new BinaryWriter(File.Open(fileName, FileMode.Create))) { for (int i = 0; i < histogramValuesList.Count; i++) { binWriter.Write(histogramValuesList[(int)i]); } binWriter.Close(); } } } _frameId++; //let only report each 100 frames for performance if (_frameId % 100 == 0) OnProgressChanged(_frameId); } } return 0; } /* int ISampleGrabberCB.SampleCB(double sampleTime, IMediaSample pSample) { Marshal.ReleaseComObject(pSample); return 0; } int ISampleGrabberCB.BufferCB(double sampleTime, IntPtr pBuffer, int bufferLen) { using (var bitmap = new Bitmap(_width, _height, _width * 3, PixelFormat.Format24bppRgb, pBuffer)) { if (!this.Secondpass) { //get avg double average = GetAveragePixelValue(bitmap); if (AveragesList == null) AveragesList = new List<double>(); //save avg AveragesList.Add(average); //***************************\\ // for (int i = 0; i < (int)framesCounts(); i++) // { // get histogram values long[] HistogramValues = Form1.GetHistogram(bitmap); if (histogramValuesList == null) histogramValuesList = new List<long>(256); histogramValuesList.AddRange(HistogramValues); long t = Form1.GetTopLumAmount(HistogramValues, 1000); //***************************\\ Form1.averagesTest.Add(t); // to add this list to a text file or binary file and read the averages from the file when its is Secondpass !!!!! //} } else { if (FramesToSave != null && FramesToSave.Contains(_frameId)) { bitmap.RotateFlip(RotateFlipType.Rotate180FlipX); bitmap.Save(Path.Combine(_outFolder, _frameId.ToString("D6") + ".bmp")); // get histogram values long[] HistogramValues = Form1.GetHistogram(bitmap); if (histogramValuesList == null) histogramValuesList = new List<long>(256); histogramValuesList.AddRange(HistogramValues); using (BinaryWriter binWriter = new BinaryWriter(File.Open(fileName, FileMode.Create))) { for (int i = 0; i < histogramValuesList.Count; i++) { binWriter.Write(histogramValuesList[(int)i]); } binWriter.Close(); } } for (int x = 1; x < Form1.averagesTest.Count; x++) { double fff = Form1.averagesTest[x] / 1000.0 - Form1.averagesTest[x - 1] / 1000.0; if (Form1.averagesTest[x] / 1000.0 - Form1.averagesTest[x - 1] / 1000.0 > 180.0) { bitmap.RotateFlip(RotateFlipType.Rotate180FlipX); bitmap.Save(Path.Combine(_outFolder, _frameId.ToString("D6") + ".bmp")); _frameId++; } } } _frameId++; //let only report each 100 frames for performance if (_frameId % 100 == 0) OnProgressChanged(_frameId); } return 0; }*/ private unsafe double GetAveragePixelValue(Bitmap bmp) { BitmapData bmData = null; try { bmData = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb); int stride = bmData.Stride; IntPtr scan0 = bmData.Scan0; int w = bmData.Width; int h = bmData.Height; double sum = 0; long pixels = bmp.Width * bmp.Height; byte* p = (byte*)scan0.ToPointer(); for (int y = 0; y < h; y++) { p = (byte*)scan0.ToPointer(); p += y * stride; for (int x = 0; x < w; x++) { double i = ((double)p[0] + p[1] + p[2]) / 3.0; sum += i; p += 3; } //no offset incrementation needed when getting //the pointer at the start of each row } bmp.UnlockBits(bmData); double result = sum / (double)pixels; return result; } catch { try { bmp.UnlockBits(bmData); } catch { } } return -1; } } public class FrameCountEventArgs { public long FrameCount { get; set; } } public class ProgressEventArgs { public int FrameID { get; set; } } } I remember i had this codec problem/s before and i installed the codec/'s that were needed but in this case both quick time and windows media player can play the video files so why the application cant detect and find the codec/'s on my computer ? Gspot say that the codec is AVC1 but again wmp and quicktime play the video files no problems. The video files are from my digital camera !

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  • [OpenGL] I'm having an issue to use GLshort for representing Vertex, and Normal.

    - by Xylopia
    As my project gets close to optimization stage, I notice that reducing Vertex Metadata could vastly improve the performance of 3D rendering. Eventually, I've dearly searched around and have found following advices from stackoverflow. Using GL_SHORT instead of GL_FLOAT in an OpenGL ES vertex array How do you represent a normal or texture coordinate using GLshorts? Advice on speeding up OpenGL ES 1.1 on the iPhone Simple experiments show that switching from "FLOAT" to "SHORT" for vertex and normal isn't tough, but what troubles me is when you're to scale back verticies to their original size (with glScalef), normals are multiplied by the reciprocal of the scale. Then how do you use "short" for both vertex and normal at the same time? I've been trying this and that for about a full day, but I could only go for "float vertex w/ byte normal" or "short vertex w/ float normal" so far. Your help would be truly appreciated.

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  • IIS7 Modules - managed or native?

    - by Simon Linder
    Hi all, as the old ISAPI filters are going to die sooner or later, I want to rewrite an old ISAPI filter that was used in IIS 6 into a module for use in IIS 7. The module will be used globally, meaning it will be used within each site, on a Windows Server 2008 R2 with IIS 7.5 installed, that will host several thousand web sites and managing about 50 application pools. My question now is if I should write that module in managed or unmanaged code? One of my concerns regarding managed code is the massive memory consumption due to the .NET framework overhead. I don't know how this would effect the server's performance. I already wrote modules in managed as well as in unmanaged code. So this is not the bothering my decision. But I would prefer to write the module in C# if there are no huge drawbacks. Any suggestions about that issue?

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  • GPU YUV to RGB. Worth the effort?

    - by Jaime Pardos
    Hello, I have to convert several full PAL videos (720x576@25) from YUV 4:2:2 to RGB, in real time, and probably a custom resize for each. I have thought of using the GPU, as I have seen some example that does just this (except that it's 4:4:4 so the bpp is the same in source and destiny)-- http://www.fourcc.org/source/YUV420P-OpenGL-GLSLang.c However, I don't have any experience with using GPU's and I'm not sure of what can be done. The example, as I understand it, just converts the video frame to YUV and displays it in the screen. Is it possible to get the processed frame instead? Would it be worth the effort to send it to the GPU, get it transformed, and sending it again to main memory, or would it kill performance? Being a bit platform-specific, assuming I work on windows, is it possible to get an OpenGL or DirectDraw surface from a window so the GPU can draw directly to it?

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  • Python: create a function to modify a list by reference not value

    - by Jonathan
    Hey all- I'm doing some performance-critical Python work and want to create a function that removes a few elements from a list if they meet certain criteria. I'd rather not create any copies of the list because it's filled with a lot of really large objects. Functionality I want to implement: def listCleanup(listOfElements): i = 0 for element in listOfElements: if(element.meetsCriteria()): del(listOfElements[i]) i += 1 return listOfElements myList = range(10000) myList = listCleanup(listOfElements) I'm not familiar with the low-level workings of Python. Is myList being passed by value or by reference? How can I make this faster? Is it possible to somehow extend the list class and implement listCleanup() within that? myList = range(10000) myList.listCleanup() Thanks- Jonathan

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  • A web framework where AJAX was not an after thought

    - by Pirate for Profit
    AJAX is a pain in the ass because it essentially means you'll have to write two sets of similarish code: one for browsers with JavaScript enabled and those without. Not only this, but you have to connect JavaScript events to hook into your models and display the results. And if all that weren't bad enough, you need to send an address change with the request, otherwise the user won't be able to "click back" correctly (if confused look at what happens to the address bar when you click links in GMail). We're searching for something that had the foresight and design goals with all these concerns in mind. Performance and security are also obvious major concerns. We love config-based systems as well, where you don't have to write a lot of code you just drop it into an easily read config format. It's like asking for the holy grail right?

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  • Throughput measurements

    - by dotsid
    I wrote simple load testing tool for testing performance of Java modules. One problem I faced is algorithm of throughput measurements. Tests are executed in several thread (client configure how much times test should be repeated), and execution time is logged. So, when tests are finished we have following history: 4 test executions 2 threads 36ms overall time - idle * test execution 5ms 9ms 4ms 13ms T1 |-*****-*********-****-*************-| 3ms 6ms 7ms 11ms T2 |-***-******-*******-***********-----| <-----------------36ms---------------> For the moment I calculate throughput (per second) in a following way: 1000 / overallTime * threadCount. But there is problem. What if one thread will complete it's own tests more quickly (for whatever reason): 3ms 3ms 3ms 3ms T1 |-***-***-***-***----------------| 3ms 6ms 7ms 11ms T2 |-***-******-*******-***********-| <--------------32ms--------------> In this case actual throughput is much better because of measured throughput is bounded by the most slow thread. So, my question is how should I measure throughput of code execution in multithreaded environment.

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  • GWT vertical layout

    - by skrat
    I need a vertical layout, which would fill browser's viewport top to bottom, with on overflow (scrollbars). I need to layout widgets on the top, and on the bottom, and have one widget in the center which would stretch to fill the remaining space. There seems to be DockLayoutPanel for this purpose, the problem with it is that it forces me to specify widget sizes, and I don't know the sizes of the top/bottom widgets before the browser does it's layouting job, which is tricky (buggy) to track. I cannot find the right moment when to measure my widgets, and I don't want to do this kind of layouting code anyway.

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  • WPF Accessing Items inside Listbox which has a UserControl as ItemTemplate

    - by Turker
    I have Window that has a ListBox ListBox(MyListBox) has a DataTable for its DataContext ListBox's ItemSource is : {Binding} Listbox has a UserControl(MyUserControl) as DataTemplate UserControl has RadioButtons and TextBoxes (At first They're filled with values from DataTable and then user can change them) Window has one Submit Button What I want to do is, when user clicks the submit button For each ListBox Item, get the values form UserControl's TextBoxes and RadioButtons. I was using that method for this job : foreach(var element in MyListBox.Items) { var border = MyListBox.ItemContainerGenerator.ContainerFromItem(element)as FrameworkElement; MyUserControl currentControl = VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(myBorder,0) as Border,0)as ContentPresenter,0)as MyUserControl; //And use currentControl } I realised nothing when using 3-5 items in Listbox. But when I used much more items, I saw that "var border" gets "null" after some elements looped in foreach function. I found the reason here : http://stackoverflow.com/questions/1675926/listview-itemcontainergenerator-containerfromitemitem-return-null-after-20-item So what can I do now? I want to access all items and get their values sitting on user controls. Thanks

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  • Are we asking too much of transactional memory?

    - by Carl Seleborg
    I've been reading up a lot about transactional memory lately. There is a bit of hype around TM, so a lot of people are enthusiastic about it, and it does provide solutions for painful problems with locking, but you regularly also see complaints: You can't do I/O You have to write your atomic sections so they can run several times (be careful with your local variables!) Software transactional memory offers poor performance [Insert your pet peeve here] I understand these concerns: more often than not, you find articles about STMs that only run on some particular hardware that supports some really nifty atomic operation (like LL/SC), or it has to be supported by some imaginary compiler, or it requires that all accesses to memory be transactional, it introduces type constraints monad-style, etc. And above all: these are real problems. This has lead me to ask myself: what speaks against local use of transactional memory as a replacement for locks? Would this already bring enough value, or must transactional memory be used all over the place if used at all?

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  • which is the best for build a Gantt-chart like application Flex or Flash Action Script?

    - by coderex
    Which is the best for build an application show like in image. For the better graphics and performance wise. I want to know Flash for Flex is more suitable for this. In Flash ca we be able to build a grid kind of applications easily? I headed that Flex have the functions to handle grid and other things. Drag & scroll Zoom like feature. but am not sure able the graphics of flex. Is the components are customizable.. Please help me.

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  • Entity framework : [Set all the entities with internal access specifier]

    - by Vedaantees
    Hi, By virtue of my application, I need to seperate my business entities from the entities created by EF4. I need to restrict the entities to only access the repository from where they are translated (using translator) to business entities shared at business and service layer. I thought of restricting them by specifying them as internal. Now there are more than 40 entities in my application so manually setting them as internal is a difficult job. In one of the forums the answers suggested using the T4 templates. But even those templates read from the entity framework access specifier. When I try to manually try to specify all the properties and class access specifiers as internal it gives me an error saying that the entity set should also be set to internal, but there is no option for the same. I am using VS 2010 and Entity Framework 4. Any suggestions???

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  • Parametrize the WHERE clause?

    - by ControlFlow
    Hi, stackoverflow! I'm need to write an stored procedure for SQL Server 2008 for performing some huge select query and I need filter it results with specifying filtering type via procedure's parameters (parameterize where clause). I found some solutions like this: create table Foo( id bigint, code char, name nvarchar(max)) go insert into Foo values (1,'a','aaa'), (2,'b','bbb'), (3,'c','ccc') go create procedure Bar @FilterType nvarchar(max), @FilterValue nvarchar(max) as begin select * from Foo as f where case @FilterType when 'by_id' then f.id when 'by_code' then f.code when 'by_name' then f.name end = case @FilterType when 'by_id' then cast(@FilterValue as bigint) when 'by_code' then cast(@FilterValue as char) when 'by_name' then @FilterValue end end go exec Bar 'by_id', '1'; exec Bar 'by_code', 'b'; exec Bar 'by_name', 'ccc'; But it doesn't work when the columns has different data types... It's possible to cast all the columns to nvarchar(max) and compare they as strings, but I think it will cause a performance degradation... Is it possible to parameterize where clause in stored procedure without using things like EXEC sp_executesql (dynamic SQL and etc.)?

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  • Best practices to build a highly configurable software product.

    - by Kabeer
    Hello. I am working on a software product that can substantially change behavior based on the configuration & meta-data supplied. I would like to know best practices to architect / build a highly configurable software product. Considering that there are substantial number of configuration parameters, I'd like to look at something that will not affect the performance before I look at dependency injection. My platform is .Net ... I seek recommendations on architecture / design and implementations fronts.

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  • Is AsParallel() good practice in a web environment?

    - by Bjorn Bailleul
    I have no doubt that for client applications, AsParallel() will bring some out-of-the-box performance gains. But what if I would use it in a web environment. Let's say I have a widget framework that loops over all widgets to get their data and render output. This would parallelize great no? I do have my doubts on using AsParallel() in this scenario. What if I have a large number of visitors for my site, isn't IIS going to use multiple threads to handle all requests? Aren't there going to be locking issues presented after a while, or threads dying because all processors are in use? It's just a thought, what do you think about this?

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  • Mirror a git repository by pulling?

    - by corydoras
    I am wondering if there is an easy way, ie like a simple cron job, to regularly pull from a remote git repository to a local read only mirror for backup purposes? Ideally it would pull all branches and tags, but the master/trunk/head would be sufficient. I just need a way to make sure that if the master git server dies, we have a backup location that we could manually fail over to. (I have been googling and reading documentation for help on how to do this for quite some time now and the furthest I have gotten is a bash script that does pull's on a regular interval.)

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  • send form data as web service in symfony

    - by Lars
    I am making a restrictive portal to a WiFi network using symfony, and I want to send a form as web service to other sites that want to use this portal. How should I solve this? I realize I could go the SOAP/WSDL route, but since symfony is already RESTful, it seems to me I could go the RESTful route with considerably less pain and loss of performance. Right now, I have a working form, but I've only made a casual attempt to bring the form to a remote site by using cURL. The form does not work remotely since the routing is not set up correctly (I think). Can someone help me with this? Thanks.

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