If some people can explain the problem to the FFTW community, I encourage you to participate to the conversation on FFTW github: https://github.com/FFTW/fftw3/pull/121.
If some people can explain the problem to the FFTW community, I encourage you to participate to the conversation on FFTW github: https://github.com/FFTW/fftw3/pull/121.