[petsc-dev] P3DFFT is an open-source numerical library providing highly scalable implementation of 3D spectral transforms

[Matthew Knepley]

On Wed, Aug 20, 2014 at 4:05 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> On Aug 20, 2014, at 4:00 PM, Matthew Knepley <knepley at gmail.com> wrote:
>
> > On Wed, Aug 20, 2014 at 3:52 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >
> > On Aug 20, 2014, at 3:34 PM, Matthew Knepley <knepley at gmail.com> wrote:
> >
> > > The blurb should also answer the question, Why do we need another FFT
> library?
> >
> >   Because it actually does multidimensional FFTs in parallel?
> >
> > For something this old and established, it might be important to say
> that it does blah
> > blah blah that Spiral, FFTW, etc.
> >
> >   In theory, with this one could write very efficient parallel 3d
> Poisson solvers in PETSc for boxes, which is an important special case that
> PETSc does not currently support.
> >
> > Wouldn't you just use MG?
>
>    FFT when done properly is much faster!  Yes it is a specialized case
> but an important one.


Are we calculating the following way:

  1) MF MG for the Laplacian is about 50 F/dof

  2) An FFT is about 6 F/dof, and we use 1 transform, 1 divide, and 1
inverse transform, so we get 13 F/dof

so you get 3x or so?

  Matt


> > I have other uses for FFT, including DFT codes where it makes a lot of
> sense.
> >
> >    Matt
> >
> >
> >   Barry
> >
> > >
> > >    Matt
> > >
> > >
> > > On Wed, Aug 20, 2014 at 1:53 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > >
> > >
> > > From: Dmitry Pekurovsky dmitry at sdsc.edu
> > > Date: August 12, 2014
> > > Subject: Library for spectral transforms in 3D for parallel machines
> > >
> > > P3DFFT is an open-source numerical library providing highly
> > > scalable implementation of 3D spectral transforms namely Fast
> > > Fourier Transform (FFT), with an option to combine it with
> > > cosine/sine/Chebyshev/empty transform in the third dimension. (The
> > > empty transform allows the user to substitute their own custom
> > > transform in the third dimension. This can be useful in
> > > applications such as inhomogeneous wall bounded turbulence.) P3DFFT
> > > implements 2D domain decomposition which allows it to overcome a
> > > scalability restriction inherent in 1D decomposition. This approach
> > > has shown good scalability up to 131,072 cores.
> > >
> > > A new version of P3DFFT 2.7.1 is now available. The project Home
> > > Page is http://code/google.com/p/p3dfft where instructions for
> > > obtaining the source code are provided. Installation instructions
> > > and a User Guide are also available.
> > >
> > > P3DFFT features include real-to-complex and complex-to-real
> > > transforms, in-place transforms, pruned transforms (with less than
> > > full input or output), and multi-variable transforms. The package
> > > includes example programs in Fortran and C. This is a project in
> > > active development, with a user mailing list, a wiki page and a
> > > version control system. P3DFFT is considered community software and
> > > is being installed in public space at many supercomputer centers.
> > > Contributions and feedback from users are welcome.
> > >
> > >
> > >
> > > --
> > > 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
> >
> >
> >
> >
> > --
> > 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
>
>


-- 
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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