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  • How are you taking advantage of Multicore?

    - by tgamblin
    As someone in the world of HPC who came from the world of enterprise web development, I'm always curious to see how developers back in the "real world" are taking advantage of parallel computing. This is much more relevant now that all chips are going multicore, and it'll be even more relevant when there are thousands of cores on a chip instead of just a few. My questions are: How does this affect your software roadmap? I'm particularly interested in real stories about how multicore is affecting different software domains, so specify what kind of development you do in your answer (e.g. server side, client-side apps, scientific computing, etc). What are you doing with your existing code to take advantage of multicore machines, and what challenges have you faced? Are you using OpenMP, Erlang, Haskell, CUDA, TBB, UPC or something else? What do you plan to do as concurrency levels continue to increase, and how will you deal with hundreds or thousands of cores? If your domain doesn't easily benefit from parallel computation, then explaining why is interesting, too. Finally, I've framed this as a multicore question, but feel free to talk about other types of parallel computing. If you're porting part of your app to use MapReduce, or if MPI on large clusters is the paradigm for you, then definitely mention that, too. Update: If you do answer #5, mention whether you think things will change if there get to be more cores (100, 1000, etc) than you can feed with available memory bandwidth (seeing as how bandwidth is getting smaller and smaller per core). Can you still use the remaining cores for your application?

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  • playing only part of a sound using FMOD

    - by carneades
    I'm trying to play only part of a sound using FMOD, say frames 50000-100000 of a 200000 frame file. I have found a couple of ways to seek forward (i.e. to start playback at frame 50000) but I have not found a way to make sure the sound stops playing at 100000. Is there any way FMOD can natively do this without having to add lbsndfile or the like into the picture? I should also mention that I am using the streaming option. I have to assume that these sounds are arbitrarily large and cannot be comfortably/quickly loaded into memory.

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  • Extrapolation using fft in octave

    - by CFP
    Using GNU octave, I'm computing a fft over a piece of signal, then eliminating some frequencies, and finally reconstructing the signal. This give me a nice approximation of the signal ; but it doesn't give me a way to extrapolate the data. Suppose basically that I have plotted three periods and a half of f: x -> sin(x) + 0.5*sin(3*x) + 1.2*sin(5*x) and then added a piece of low amplitude, zero-centered random noise. With fft/ifft, I can easily remove most of the noise ; but then how do I extrapolate 3 more periods of my signal data? (other of course that duplicating the signal). The math way is easy : you have a decomposition of your function as an infinite sum of sines/cosines, and you just need to extract a partial sum and apply it anywhere. But I don't quite get the programmatic way... Thanks!

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  • User avatar cropping/resizing with paperclip and jquery in rails

    - by Micke
    Hello fellow stackoverflow users. I am building my first Ruby on Rails app which is going to be my own little community. I have made the User model with several fields and information. But now i am thinking of adding avatar support for the users. And i've been researching and found that my best option would be using Paperclip. But then i've encountered a little dilemma. I want my users to be able to resie/crop their avatar image after they have chosen a image. I have googled alot and since i am using jQuery i found that imgAreaSelect would be best in my opinion. And i think MiniMagick looks best. So to my question. How can i best intergrate Paperclip and imgAreaSelect? I am new to Ruby and Rails so i don't know how i can resize the image. Do you folks know how to intergrate the to or maybe some other options that fits my needs best? I also need to apologize for my bad/misspelled english since i am not english :) Thanking you in advance. Yours sincerely, Micke.

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  • Playing sounds in iPhone SDK?

    - by seanny94
    Does anyone have a snippet that uses the AudioToolBox framework that can be used to play a short sound? I would be grateful if you shared it with me and the rest of the community. Everywhere else I have looked doesn't seem to be too clear with their code. Thanks!

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  • Marker Recognition on Android (recognising Rubik's Cubes)

    - by greenie
    Hi everybody. I'm developing an augmented reality application for Android that uses the phone's camera to recognise the arrangement of the coloured squares on each face of a Rubik's Cube. One thing that I am unsure about is how exactly I would go about detecting and recognising the coloured squares on each face of the cube. If you look at a Rubik's Cube then you can see that each square is one of six possible colours with a thin black border. This lead me to think that it should be relativly simply to detect a square, possibly using an existing marker detection API. My question is really, has anybody here had any experience with image recognition and Android? Ideally I'd like to be able to implement and existing API, but it would be an interesting project to do from scratch if somebody could point me in the right direction to get started. Many thanks in advance.

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  • J2ME Camera and Sound Recorder Access On A Windows Mobile

    - by Steven Knox
    I'm currently involved in a research project that requires me to access a Windows Mobile Camera and sound recorder with J2ME to, well take pictures and record sound... the phone has to be a windows mobile for some reason that has nothing to do with me and the software has to be written in Java, also not my decision. So I need to try and find a phone that supports this (if one exists) so I'd like to know if anyone has found one? Thank You For Your Help. (Note the phone supporting MMAPI (JSR 135) does not imply that you can use the camera and sound recorder, our current phone has this and has not access).

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  • TMS320C64x Quick start reference for porgrammers

    - by osgx
    Hello Is thare any quickstart guide for programmers for writing DSP-accelerated appliations for TMS320C64x? I have a program with custom algorythm (not the fft, or usial filtering) and I want to accelerate it using multi-DSP coprocessor. So, how should I modify source to move computation from main CPU to DSPs? What limitations are there for DSP-running code? I have some experience with CUDA. In CUDA I should mark every function as being host, device, or entry point for device (kernel). There are also functions to start kernels and to upload/download data to/from GPU. There are also some limitations, for device code, described in CUDA Reference manual. I hope, there is an similar interface and a documentation for DSP.

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  • How to use ImageMagick to batch desaturate images?

    - by Zando
    I have an image that is black text with some gray and pale yellowish background. I basically want to keep the text as black as possible, and make the gray and yellow comparatively lighter...at the very least, turn yellow into a light gray. What's the most efficient way to do that in ImageMagick?

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  • Calculating length of objects in binary image - algorithm

    - by Jacek
    I need to calculate length of the object in a binary image (maximum distance between the pixels inside the object). As it is a binary image, so we might consider it a 2D array with values 0 (white) and 1 (black). The thing I need is a clever (and preferably simple) algorithm to perform this operation. Keep in mind there are many objects in the image. The image to clarify: Sample input image:

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  • Copy & rename file using .bat file language?

    - by flyout
    I want to make a .bat to copy & rename a file multiple times. I want to have a list of names, and an original file, then I want to copy that file and rename it for each name on the list. How I can do this using a .bat file? Also is it possible to run winrar fromthe .bat to .rar or .zip every file after copying/renaming?

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  • convert RGB values to equivalent HSV values using python

    - by sree01
    Hi, I want to convert RGB values to HSV using python. I got some code samples, which gave the result with the S and V values greater than 100. (example : http://code.activestate.com/recipes/576554-covert-color-space-from-hsv-to-rgb-and-rgb-to-hsv/ ) . anybody got a better code which convert RGB to HSV and vice versa thanks

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  • Record AVAudioPlayer output using AVAudioRecorder

    - by Kieran
    In my app the user plays a sound by pressing a button. There are several buttons which can be played simultaneously. The sounds are played using AVAudioPlayer instances. I want to record the output of these instances using AVAudioRecorder. I have set it all up and a file is created and records but when I play it back it does not play any sound. It is just a silent file the length of the recording. Does anyone know if there is a setting I am missing with AVAudioPlayer or AVAudioRecorder? Thanks

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  • Image Comparision

    - by harigm
    How do I compare the 2 images in Java based web application. I have installed the Biometric thumb reader, I need to read the user Thumb and compare it with his thumb image which is captured during the registration process. Initially I am storing the image in the Mysql as Blob. Else I can store that image in a separate folder as well Please suggest which is best way to do 1)Shall i Use the Java script 2)Is there any built in Java API to perform this

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  • How to produce precisely-timed tone and silence in C#

    - by Bob Denny
    I have a C# project that plays Morse code for RSS feeds. I write it using Managed DirectX, only to discover that Managed DirectX is old and deprecated. The task I have is to play pure sine wave bursts interspersed with silence periods (the code) which are precisely timed as to their duration. I need to be able to call a function which plays a pure tone for so many milliseconds, then Thread.Sleep() then play another, etc. At its fastest, the tones and spaces can be as short as 40ms. It's working quite well in Managed DirectX. To get the precisely timed tone I create 1 sec. of sine wave into a secondary buffer, then to play a tone of a certain duration I seek forward to within x milliseconds of the end of the buffer then play. I've tried System.Media.SoundPlayer. It's a loser because you have to Play(), Sleep(), then Stop() for arbitrary tone lengths. The result is a tone that is too long, variable by CPU load. It takes an indeterminate amount of time to actually stop the tone. I then embarked on a lengthy attempt to use NAudio 1.3. I ended up with a memory resident stream providing the tone data, and again seeking forward leaving the desired length of tone remaining in the stream, then playing. This worked OK on the DirectSoundOut class for a while (see below) but the WaveOut class quickly dies with an internal assert saying that buffers are still on the queue despite PlayerStopped = true. This is odd since I play to the end then put a wait of the same duration between the end of the tone and the start of the next. You'd think that 80ms after starting Play of a 40 ms tone that it wouldn't have buffers on the queue. DirectSoundOut works well for a while, but its problem is that for every tone burst Play() it spins off a separate thread. Eventually (5 min or so) it just stops working. You can see thread after thread after thread exiting in the Output window while running the project in VS2008 IDE. I don't create new objects during playing, I just Seek() the tone stream then call Play() over and over, so I don't think it's a problem with orphaned buffers/whatever piling up till it's choked. I'm out of patience on this one, so I'm asking in the hopes that someone here has faced a similar requirement and can steer me in a direction with a likely solution. Thanks in advance...

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  • NAudio playback wont stop successfully

    - by Kurru
    Hi When using NAudio to playback an mp3 [in the console], I cant figure out how to stop the playback. When I call waveout.Stop() the code just stops running and waveout.Dispose() never gets called. Is it something to do with the function callback? I dont know how to fix that if it is. static string MP3 = @"song.mp3"; static WaveOut waveout; static WaveStream playback; static void Main(string[] args) { waveout = new WaveOut(WaveCallbackInfo.FunctionCallback()); playback = OpenMp3Stream(MP3); waveout.Init(playback); waveout.Play(); Console.WriteLine("Started"); Thread.Sleep(2 * 1000); Console.WriteLine("Ending"); if (waveout.PlaybackState != PlaybackState.Stopped) waveout.Stop(); Console.WriteLine("Stopped"); waveout.Dispose(); Console.WriteLine("1st dispose"); playback.Dispose(); Console.WriteLine("2nd dispose"); } private static WaveChannel32 OpenMp3Stream(string fileName) { WaveChannel32 inputStream; WaveStream mp3Reader = new Mp3FileReader(fileName); WaveStream pcmStream = WaveFormatConversionStream.CreatePcmStream(mp3Reader); WaveStream blockAlignedStream = new BlockAlignReductionStream(pcmStream); inputStream = new WaveChannel32(blockAlignedStream); return inputStream; }

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  • selecting the pixels from an image in opencv

    - by ajith
    hi everyone, this is refined version of my previous question http://stackoverflow.com/questions/2602628/computing-matting-laplacian-matrix-of-an-image actually i want to do following operation... summation for all k|(i,j)?wk [(Ii-µk)*(Ij-µk)]...where wk is 3X3 window & µk is mean of wk...here i dont know how to select Ii & Ij separately from an image which is 2 dimensional[Iij]...or does the eqn means anything else??please someone help me..

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  • perl multiple tasks problem

    - by Alice Wozownik
    I have finished my earlier multithreaded program that uses perl threads and it works on my system. The problem is that on some systems that it needs to run on, thread support is not compiled into perl and I cannot install additional packages. I therefore need to use something other than threads, and I am moving my code to using fork(). This works on my windows system in starting the subtasks. A few problems: How to determine when the child process exits? I created new threads when the thread count was below a certain value, I need to keep track of how many threads are running. For processes, how do I know when one exits so I can keep track of how many exist at the time, incrementing a counter when one is created and decrementing when one exits? Is file I/O using handles obtained with OPEN when opened by the parent process safe in the child process? I need to append to a file for each of the child processes, is this safe on unix as well. Is there any alternative to fork and threads? I tried use Parallel::ForkManager, but that isn't installed on my system (use Parallel::ForkManager; gave an error) and I absolutely require that my perl script work on all unix/windows systems without installing any additional modules.

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  • C# manipulating video

    - by grey88
    i want to take a folder of pictures, and turn it into a slideshow video with music in the background. i have no idea how to do this, or where to get help, cos this isnt the kind of thing you can search in google. idk if there are api's for it, or if it can even be done in C#. maybe ill have to move the project to C++ or something, but first i need to know where the hell to start. thanks.

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  • Simplex noise vs Perlin noise

    - by raRaRa
    I would like to know why Perlin noise is still so popular today after Simplex came out. Simplex noise was made by Ken Perlin himself and it was suppose to take over his old algorithm which was slow for higher dimensions and with better quality (no visible artifacts). Simplex noise came out in 2001 and over those 10 years I've only seen people talk of Perlin noise when it comes to generating heightmaps for terrains, creating procedural textures, et cetera. Could anyone help me out, is there some downside of Simplex noise? I heard rumors that Perlin noise is faster when it comes to 1D and 2D noise, but I don't know if it's true or not. Thanks!

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  • How to overwirte i-frames of a video?

    - by Dominik
    hi, i want to destroy alle i-frames of a video. doing this i want to check if encrypting only the i-frames of a video would be sufficient for making it unwatchable. How can i do this? Only removing them and recompressing the video would not be the same as really overwriting the iframe in the stream without recalculating b-frames etc.

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