[petsc-dev] Dev release GPU solvers

[Randall Mackie]

On Sep 6, 2011, at 9:16 AM, Matthew Knepley wrote:

> On Tue, Sep 6, 2011 at 11:12 AM, Randall Mackie <rlmackie862 at gmail.com> wrote:
> 
> On Sep 6, 2011, at 9:08 AM, Barry Smith wrote:
> 
> >
> >
> > On Sep 6, 2011, at 10:59 AM, Daniel Lowell wrote:
> >
> >> On this page: http://www.mcs.anl.gov/petsc/petsc-as/features/gpus.html
> >>
> >> It states: "All of the Krylov methods except KSPIBCGS run on the GPU."
> >> I actually could only find ksp/pc/bicgstabcusp for any ksp implementation on the GPU.
> >
> >  Daniel,
> >
> >     All the vector operations and the matrix-vector product used by the Krylov methods implemented in PETSc (except KSPIBCGS) run on the GPU without copying up or down vector or matrix values, in the same way as ksp/pc/bicgstabcusp does, hence we say they run on the GPU. In fact, in our tests our BiGCStab runs just as fast as the Nvidia CUSP code ksp/pc/bicgstabcusp.
> >
> >    In other words, higher level algorithms such as Krylov methods and Newton methods do not need to be "written for the GPU", so long as the kernel operations run on the GPU.
> >
> >
> >
> >   Barry
> 
> Barry,
> 
> But is this still only for real data types? Last time I checked, earlier this year, complex valued data were not
> supported under PETSc, even though complex data types are supported in CUSP.
> 
> I have not tried, but I do not understand why it would not work. We just use PetscScalar. Can you send
> the problem you found?
> 
>    Matt


Matt,

Here is the message that I received earlier this year, but I never did have time to follow up on it then:


> From: Barry Smith <bsmith at mcs.anl.gov>
> Date: May 24, 2011 5:04:51 AM PDT
> To: petsc-maint at mcs.anl.gov, Victor Minden <victorminden at gmail.com>
> Cc: Randall Mackie <rlmackie862 at gmail.com>
> Subject: Re: [petsc-maint #71751] error during compile
> 
> 
>  Victor,
> 
>     Thanks for the info. I've forgotten about the blas.  
> 
>  Randall,
> 
>      Looks like it is not so trivial as I had made it out to be. Perhaps if you ask on petsc-dev at mcs.anl.gov there may be people who want this also and are willing to share the work?
> 
>   Barry
> 
> On May 23, 2011, at 6:06 PM, Victor Minden wrote:
> 
>> Barry,
>> 
>> Currently there should be two things going on--one is that some of the
>> CUBLAS routines used for basic vector operations (which we've been moving
>> away from) have 4 different forms depending on single/double and
>> real/complex--currently those that we still use are hard-coded as real and
>> #ifdeffed to be single/double, and I haven't looked in depth but I think
>> those are the errors that Randy sent.
>> 
>> Those should be pretty quick to change, but they won't make complex work,
>> because once you get past veccusp.cu there are a bunch more errors in the
>> cusp matrix routines which work with complex if you use the relatively new
>> (Oct?  Dec?) cusp complex type that they've added to the cusp library.  So,
>> we need to make the GPU routines work with the standard complex type or we
>> need to convert all the GPU code to use the cusp type.  I don't know how
>> much work this is.
>> 
>> As it stands, I'm just starting my internship this week so I probably won't
>> be able to look at this in-depth until the weekend, just FYI.
>> 
>> Cheers,
>> 
>> Victor
>> ---
>> Victor L. Minden
>> 
>> Tufts University
>> School of Engineering
>> Class of 2012
>> 




>  
> Randy
> 
> 
> >
> >>
> >> CUSP does have everything mentioned in the above PETSc link:
> >> http://code.google.com/p/cusp-library/wiki/QuickStartGuide#Iterative_Solvers
> >>
> >> However I don't see where any of it is implemented in the latest Dev release, Krylov solvers or preconditioners.
> >>
> >> Can anyone clear this up for me?
> >>
> >> Thanks,
> >>
> >> Daniel Lowell
> >
> 
> 
> 
> 
> -- 
> 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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