GPGPU status

[Ben Levine]

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