[petsc-users] Using PFFT within PETSc

[Matthew Knepley]

On Mon, Nov 23, 2015 at 1:31 AM, Giuseppe Pitton <gpitton at sissa.it> wrote:

> Dear users and developers,
> I am trying to interface PETSc with the parallel fast Fourier transform
> library PFFT (
> https://www-user.tu-chemnitz.de/~potts/workgroup/pippig/software.php.en),
> based in turn on FFTW. My plan is to build a spectral differentiation code,
> and in the attached files you can see a simple example.
>

Is it possible to write this example using the existing calls?


http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateFFT.html

That way we would have a baseline we could both run that works, and then we
could look
at something broken.

  Thanks,

     Matt


> The code works correctly in serial, but in parallel there are some
> problems regarding the output of the results, I think due to some
> differences in the way PETSc and PFFT store data, but I'm not sure if this
> is really the issue.
> In the attached code, the number of processors used should be specified at
> compile time in the variable "ncpus". As long as ncpus = 1, everything
> works fine, but if ncpus = 2 or an higher power of 2, the code terminates
> correctly but the results show some artifacts, as you can see from the
> generated hdf5 file, named "output-pfft.h5".
> In the makefile the variables PFFTINC, PFFTLIB, FFTWINC and FFTWLIB should
> be set correctly.
> Thank you,
> Giuseppe
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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