On Wed, Aug 20, 2014 at 4:12 PM, Barry Smith <[email protected]> wrote:
> > On Aug 20, 2014, at 4:08 PM, Matthew Knepley <[email protected]> wrote: > > > On Wed, Aug 20, 2014 at 4:05 PM, Barry Smith <[email protected]> wrote: > > > > On Aug 20, 2014, at 4:00 PM, Matthew Knepley <[email protected]> wrote: > > > > > On Wed, Aug 20, 2014 at 3:52 PM, Barry Smith <[email protected]> > wrote: > > > > > > On Aug 20, 2014, at 3:34 PM, Matthew Knepley <[email protected]> > 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? > > My statement is based on experience, not models. I stand by it and yes > it can be factors of that magnitude. Now one could argue 3 times faster so > what, but if you are doing this solve millions of times and it is the most > time consuming part of the simulation (by far) then it adds up. If you write the installer, I will get all the beer when you come up to my house to hear Jack talk on Oct. 2 Matt > > 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 <[email protected]> > wrote: > > > > > > > > > > > > From: Dmitry Pekurovsky [email protected] > > > > 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 > > -- 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
