No, PETSc direct solvers do not work in parallel. Only SuperLU_DIST, MUMPS,
and PasTix.
-pc_type lu (or cholesky depending on the package)
-pc_factor_mat_solver_type superlu_dist or mumps or pastix
to run the direct solver in parallel.
> On Jul 28, 2020, at 9:01 PM, Bin Liu <[email protected]> wrote:
>
> Dear Barry,
>
> Thanks for your explanation. Does it mean the default director solver LU in
> PETSc can also run in the distributed memory mode? I only used iterative
> solvers with preconditioners in distributed memory before. My experience in
> using director solver in parallel is indeed limited, especially the saddle
> point problem in parallel. I have done some search online, but I did not find
> a working set up at this moment. Could you give a sample setup of the direct
> solver for parallel run? It is really appreciated.
> <>
> From: Barry Smith [mailto:[email protected]]
> Sent: Wednesday, 29 July 2020 9:48 AM
> To: Bin Liu <[email protected]>
> Cc: [email protected]
> Subject: Re: [petsc-users] solving saddle point problem in distributed memory
>
>
> SuperLU_DIST won't "magically" run on saddle point problems. It only does
> limited pivoting, realistically a parallel LU cannot always do complete
> pivoting or it becomes a sequential algorithm. For parallel you need to use
> PCFIELDSPLIT, for sequential you can use SuperLU (not SuperLU_DIST) since it
> can do more pivoting, being a sequential algorithm.
>
> Barry
>
>
>
> On Jul 28, 2020, at 7:59 PM, Bin Liu <[email protected]
> <mailto:[email protected]>> wrote:
>
> Thanks for your tutorials. Yes. I tried PCFIELDSPLIT. However, it only works
> for sequential runs. When I run the code in distributed memory, it reports
> errors. In fact, the essence of my wonder is (a) how to set up superlu_dist
> in petsc for solving saddle point problem in distributed memory? (b) does the
> direct solvers in petsc can run in distributed memory for solving saddle
> point problem?
>
> From: Stefano Zampini [mailto:[email protected]
> <mailto:[email protected]>]
> Sent: Tuesday, 28 July 2020 6:55 PM
> To: Bin Liu <[email protected] <mailto:[email protected]>>
> Cc: [email protected] <mailto:[email protected]>
> Subject: Re: [petsc-users] solving saddle point problem in distributed memory
>
> If you want advice you should post the error trace PETSc reports.
>
> Anyway, solving Stokes is not so trivial (without direct solvers, you may
> need mesh dependent information), but we have examples for it
>
> https://gitlab.com/petsc/petsc/-/blob/master/src/ksp/ksp/tutorials/ex42.c
> <https://gitlab.com/petsc/petsc/-/blob/master/src/ksp/ksp/tutorials/ex42.c>
> https://gitlab.com/petsc/petsc/-/blob/master/src/ksp/ksp/tutorials/ex43.c
> <https://gitlab.com/petsc/petsc/-/blob/master/src/ksp/ksp/tutorials/ex43.c>
> https://gitlab.com/petsc/petsc/-/blob/master/src/snes/tutorials/ex69.c
> <https://gitlab.com/petsc/petsc/-/blob/master/src/snes/tutorials/ex69.c>
>
> If you scroll to the end of those files, you see a bunch of possible options
> either using PCFIELDSPLIT, PCBDDC or KSPFETIDP.
>
>
>
>
> On Jul 28, 2020, at 12:37 PM, Bin Liu <[email protected]
> <mailto:[email protected]>> wrote:
>
> I would like to solve a saddle point problem arising from the stokes
> equation. I got successful to use the direct solvers in sequential runs.
> However, I would like to extend it for distributed memory computation. I
> tried to use superlu_dist, but the program returns errors. Is it possible to
> solve a saddle point problem in distributed memory using superlu_dist? Could
> anyone give a simple sample code to set up the parameters of the solver?
>
> Thanks
>
