# gather data from processors in FFTW3 MPI

The parallel FFTW3 distributes different portions of a large data to different processors, so that each processor obtains and manipulates only a small fraction of the large size data that wants to be fourier transformed.

I am wondering, at the end of the transformation, as the transformed data are locating at different processors, is there any built-in routine in FFTW3 to gather all these small portions from different processors to recover the entire data set, for example, at the root processor. Hope this question is clear to you guys and I am looking forward to your suggestions.

• thanks, Bill. I think it might be good and, actually, easy for FFTW3 to include such routines. But, you are right, MPI does the same thing. – Katuru Mar 13 '14 at 13:08

I don't think that there's an FFTW3 routine that does this, but there's always MPI_Gather() in the MPI library. Of course, it's possible that you may not be able to gather all the data to a single processor because it is too big to fit there.