[Discuss-gnuradio] Pathological FFT sizes

[Marcus D. Leech]

I discovered, rather by accident, that the FFTW planner seems to get its
knickers royally in a twist for certain FFT sizes.  The code
    d_plan = fftwf_plan_dft_1d (fft_size,
                              reinterpret_cast<fftwf_complex *>(d_inbuf),
                              reinterpret_cast<fftwf_complex *>(d_outbuf),
                              forward ? FFTW_FORWARD : FFTW_BACKWARD,
                              FFTW_MEASURE);

Goes away and computes forever for FFT sizes of 3200000 and 6400000.  I
know that FFTW tries to compute
  and "optimized" algorithm based on size, etc.  I guess that there are
singularities in the optimizer??

I was trying to add various sizes other than {1,2,4,8}M bins, with 3.2M
and 6.4M being obvious intermediate
  sizes, which seems to have provoked this problem.   I'm running with
FFTW-3.2. 

-- 
Marcus Leech
Principal Investigator, Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org