GPGPU status

[Ben Levine]

Okay, now that the FFTSGL situation is fixed it seams that the CUDA
compile is working again.  Give the latest CVS version a shot if you
are interested, and please let me know if you have any problems or
successes...  Particularly successes.

On Feb 5, 4:21 pm, Ben Levine <ben.l... at gmail.com> wrote:
> Hi Guys,
> Sorry to be joining the discussion a little late.  I haven't checked
> the group in a little while, I guess.
>
> Yes, I've done some work in incorperating some CUDA code into CP2K,
> and after a long hiatus I am just starting to work on it again.  Right
> now it is possible to run CP2K with a single precision FFT and several
> associated scatter/gather operations run on the GPU.  As others have
> said, running the FFT in single precision does not seem to degrade the
> accuracy of the calculation significantly.  In my experience this
> can't be said for other portions of the code, and this is the reason
> that greater CUDA support is not yet provided.
>
> To enable CUDA support compile with the -D__CUDA and -D__FFTSGL
> compiler flags...  But hold off for a little bit if you would.  I'm
> currently having some problems getting it to run in it's current
> state.  I'll post again when it's working.  Thanks for your interest.
>
> Ben
>
> On Jan 29, 8:59 am, Juerg Hutter <hut... at pci.uzh.ch> wrote:
>
> > Hi
>
> > > I am interested in the status of GPGPU code in CP2K. So far, I have
> > > found only the very brief mention of single precision FFT using CUDA in
> > > the input manual and this e-mail from the CPMD archive:
>
> > >http://www.cpmd.org/pipermail/cpmd-list/2008-April/004330.html
>
> > > Could someone please give me a brief overview of the options one has in
> > > this area in CP2K? I would also like to know whether there is someone
> > > working on some sort of GPGPU code at this time.
>
> > we have been looking into this a couple of times and also have some
> > accelerator cards available. Up to now we couldn't find a convincing
> > application, meaning a project together with a hardware setup where
> > the work/benefit ratio is good.
>
> > > I also have one more specific question. Could FFTCU be adapted to use
> > > double precision capable cards? I am interested in this because of
> > > cluster calculations in open boundary conditions, where FFT seems to be
> > > the main bottleneck. Also, does anyone have any experience using FFTCU?
>
> > we have some (but not comprehensive) experience with a setup where all
> > of CP2K is running double precicion except for the FFT. (compile with
> > -D__FFTSGL)
> > It seems that the loss in accuracy is not dramatic and this might be
> > an interesting option if a really fast single precision FFT is available.
>
> > regards
>
> > Juerg Hutter
>
> > > Thanks a lot for any replies or comments,
> > > Ondrej