[petsc-dev] GPU based preconditioner and PCSHELL

[Matthew Knepley]

On Fri, Dec 2, 2011 at 6:20 PM, Dave Nystrom
<Dave.Nystrom at tachyonlogic.com>wrote:

> I never received any reply to this question but would very much appreciate
> one.  Not sure if it fell through the cracks.
>

you can do whatever you want in PCSHELL. I would look at sacusp, since this
does about
what you want.

  Matt


> Thanks,
>
> Dave
>
> Dave Nystrom writes:
>  > I have a 2d resistive mhd code interfaced to petsc.  The code has seven
>  > different linear solves per timestep and these linear solves consume
> around
>  > 95 percent of the run time for a reasonably small grid of 100x301.  The
> run
>  > time is dominated by the solution of one of the linear solves that is
>  > particularly difficult to solve.  This particular linear solve actually
> takes
>  > about 80 percent of the total run time.  All of these linear systems are
>  > symmetric.  I am actually able to run a simulation where I am using
> jacobi
>  > preconditioning with conjugate gradient on a gpu and get a solution and
> this
>  > is the fastest solution which I currently get but the iteration count
> ranges
>  > from a minimum of 771 to a max of 47300 for the difficult linear system.
>  >
>  > We also have a native cg solver in the code which uses a full cholesky
> band
>  > solve of the inner set of bands and that solver has a much better
> iteration
>  > count although it takes a bit over 2x the run time of petsc w/ jacobi
> and
>  > cusp.  So, I have been interested in making a custom petsc
> preconditioner
>  > that does this cholesky solve using the PCSHELL capability of petsc.
>  And I'm
>  > interested in trying to do this cholesky solve on the GPU using a CULA
> SPARSE
>  > band solver.  However, I'm wondering if the petsc PCSHELL capability
> only
>  > runs on the cpu and if I would need a GPU analog such as a PCGPUSHELL
>  > capability in petsc.  I'm wondering if this is the case and if so,
> whether
>  > there is a possibility that a PCGPUSHELL capability might be added to
> petsc
>  > in the near term.
>  >
>  > Thanks,
>  >
>  > Dave
>  >
>  > --
>  > Dave Nystrom
>  >
>  > phone: 505-661-9943 (home office)
>  >        505-662-6893 (home)
>  > skype: dave.nystrom76
>  > email: dnystrom1 at comcast.net
>  > smail: 219 Loma del Escolar
>  >        Los Alamos, NM 87544
>



-- 
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20111202/a43d84d4/attachment.html>