fftw | 易学教程

fftw in Visual Studio?

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I'm trying to link my project with fftw and so far, I've gotten it to compile, but not link. As the site said, I generated all the .lib files (even though I'm only using double precision), and copied them to C:\Program Files\Microsoft Visual Studio 9.0\VC\lib , the .h file to C:\Program Files\Microsoft Visual Studio 9.0\VC\include and the .dll to C:\windows\system32 . I've copied the tutorial program, and the exact error I am getting is: 1>hw10.obj : error LNK2019: unresolved external symbol __imp__fftw_free referenced in function "bool __cdecl test(void)" (?test@@YA_NXZ) 1>hw10.obj : error

Recent FFTW wrapper in Java

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问题 I'm seeking a minimal Java wrapper for a recent version of FFTW. The wrappers listed on the FFTW website are either out of date (jfftw-1.2.zip) or contain too much extra stuff (Shared Scientific Toolbox). A Google search suggests JFFTW3, which looks promising, but the download link is broken (does anybody have a mirror?) For those who want a pure Java FFT library, JTransforms looks very good. I'd prefer to use FFTW because it's about twice as fast, and it handles arbitrary dimensions d > 3.

Why is cuFFT so slow?

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问题 I'm hoping to accelerate a computer vision application that computes many FFTs using FFTW and OpenMP on an Intel CPU. However, for a variety of FFT problem sizes, I've found that cuFFT is slower than FFTW with OpenMP. In the experiments and discussion below, I find that cuFFT is slower than FFTW for batched 2D FFTs. Why is cuFFT so slow, and is there anything I can do to make cuFFT run faster? Experiments (code download) Our computer vision application requires a forward FFT on a bunch of

Forward FFT an image and backward FFT an image to get the same result

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问题 I am trying to FFT an image using the library from http://www.fftw.org/ so that I can do a convolution in the frequency domain. But I can't figure out how to make it work. To understand how to do this I am trying to forward FFT an image as an array of pixelcolors and then backward FFT it to get the same array of pixelcolors. Here's what I do: fftw_plan planR, planG, planB; fftw_complex *inR, *inG, *inB, *outR, *outG, *outB, *resultR, *resultG, *resultB; //Allocate arrays. inR = (fftw_complex*

Why is FFT of (A+B) different from FFT(A) + FFT(B)?

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问题 I have been fighting with a very weird bug for almost a month. Asking you guys is my last hope. I wrote a program in C that integrates the 2d Cahn–Hilliard equation using the Implicit Euler (IE) scheme in Fourier (or reciprocal) space: Where the "hats" mean that we are in Fourier space: h_q(t_n+1) and h_q(t_n) are the FTs of h(x,y) at times t_n and t_(n+1), N[h_q] is the nonlinear operator applied to h_q, in Fourier space, and L_q is the linear one, again in Fourier space. I don't want to go

Recent FFTW wrapper in Java

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I'm seeking a minimal Java wrapper for a recent version of FFTW . The wrappers listed on the FFTW website are either out of date ( jfftw-1.2.zip ) or contain too much extra stuff ( Shared Scientific Toolbox ). A Google search suggests JFFTW3 , which looks promising, but the download link is broken (does anybody have a mirror?) For those who want a pure Java FFT library, JTransforms looks very good. I'd prefer to use FFTW because it's about twice as fast, and it handles arbitrary dimensions d > 3. I ended up using JNAerator to automatically generate JNA bindings from the header file fftw3.h .

Why I cannot override search path of dynamic libraries with LD_LIBRARY_PATH?

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问题 Edit: I resolved this issue, the solution is below. I am building a code in a shared computing cluster dedicated for scientific computing, thus I can only control files in my home folder. Although I am using fftw as an example, I would like to understand the specific reason, why my attempt to setup LD_LIBRARY_PATH does not work. I build the fftw and fftw_mpi libraries in my home folder like this ./configure --prefix=$HOME/install/fftw --enable-mpi --enable-shared make install It builds fine,

Why is cuFFT so slow?

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I'm hoping to accelerate a computer vision application that computes many FFTs using FFTW and OpenMP on an Intel CPU. However, for a variety of FFT problem sizes, I've found that cuFFT is slower than FFTW with OpenMP. In the experiments and discussion below, I find that cuFFT is slower than FFTW for batched 2D FFTs. Why is cuFFT so slow, and is there anything I can do to make cuFFT run faster? Experiments ( code download ) Our computer vision application requires a forward FFT on a bunch of small planes of size 256x256. I'm running the FFTs on on HOG features with a depth of 32, so I use the

FFTW vs. OpenCV cvDFT

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Can I expect a speedup when using FFTW (http://www.fftw.org/) instead of OpenCV's cvDFT (http://goo.gl/YCHj0)? My program's runtime is heavily determined by the application of inverse and forward DFT and I am thinking about using FFTW instead of OpenCV cvDFT. IIRC FFTW does some kind of "runtime compilation" whereas cvDFT is a simple FFT implementation, so I guess it could speed up my processing a bit. So before I am trying it out by myself, I thought to ask in here in case anyone stumbled over the same question and solved it before. Thanks in advance I have used both (OpenCV and FFTW) and you

generating correct spectrogram using fftw and window function

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For a project I need to be able to generate a spectrogram from a .WAV file. I've read the following should be done: Get N (transform size) samples Apply a window function Do a Fast Fourier Transform using the samples Normalise the output Generate spectrogram On the image below you see two spectrograms of a 10000 Hz sine wave both using the hanning window function. On the left you see a spectrogram generated by audacity and on the right my version. As you can see my version has a lot more lines/noise. Is this leakage in different bins? How would I get a clear image like the one audacity