[petsc-dev] GPU based preconditioner and PCSHELL

Dave Nystrom Dave.Nystrom at tachyonlogic.com
Fri Dec 2 18:20:29 CST 2011

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



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

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