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c++matlabfftw

FFTW Function n2fv_64

I am reviewing the behavior of MATLAB's 2D FFT routine fft2 on a 64x64 matrix. I found that when computing the 2D FFT (using FFTW) MATLAB R2010b creates two routines in the wisdom:

>> fftw('dwisdom')

ans =

(FFTW-3.2.2 fftw_wisdom
  (fftw_codelet_r2cf_64 2 #x30bff #x30bff #x0 #x72951e17 #x27eedd0a #xf6808210 #x72916df6)
  (fftw_codelet_n2fv_64 0 #x30bff #x30bff #x0 #x6c6e1d55 #xa8591917 #x7af2b07e #x820c2895)
)

I understand that the r2cf is indicating a real-to-complex transformation but I am unfamiliar with the n2fv. Searching for n2fv resulted in finding the n2fv_64 function in n2fv_64.c but I did not see a definition.

What is the purpose of the FFTW function n2fv_64(...) (found in at least \dft\simd\common\n2fv_64.c) and why did MATLAB create this in the wisdom?

Solution

  • The n2fv_64 stands for the forward discrete Fourier transform (fv=forward vector).