[petsc-users] questions on hypre preconditioner

[Fande Kong]

Thanks, Barry.


On Mon, Sep 5, 2016 at 11:26 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> > On Sep 5, 2016, at 11:21 AM, Fande Kong <fdkong.jd at gmail.com> wrote:
> >
> > Hi Developers,
> >
> > There are two questions on the hypre preconditioner.
> >
> > (1) How to set different relax types on different levels? It looks to
> use the SAME relax type on all levels except the coarse level which we
> could set it to a different solver. Especially, could I set the smoother
> type on the finest level as NONE?
>
>    I don't think this is possible through the PETSc interface; it may or
> may not be possible by adding additional hypre calls. You need to check the
> hypre documentation.
>

I already took a look into the hypre code. It is not easy to change. But
there is a way to do that. I already figured out a way to extract
interpolation, restriction  and coarse operators from hypre. I could
construct any algorithms I want with these operators.

The question is: any existing ways to convert a parallel hypre matrix to a
petsc Mat, and the same operations for vectors?


>
> >
> > (2) How could I know how many levels have been actually created in
> hypre, and how many unknowns on different levels?   The "-pc_view" can not
> tell me this information:
>
> -pc_hypre_boomeramg_print_statistics integer  different integers give
> different amounts of detail, I don't know what the integers mean.
>

we could get all information by extracting data from hypre_solver.

Fande,

>
>
>
>
>
> >
> >  type: hypre
> >                         HYPRE BoomerAMG preconditioning
> >                         HYPRE BoomerAMG: Cycle type V
> >                         HYPRE BoomerAMG: Maximum number of levels 25
> >                         HYPRE BoomerAMG: Maximum number of iterations
> PER hypre call 1
> >                         HYPRE BoomerAMG: Convergence tolerance PER hypre
> call 0
> >                         HYPRE BoomerAMG: Threshold for strong coupling
> 0.25
> >                         HYPRE BoomerAMG: Interpolation truncation factor
> 0
> >                         HYPRE BoomerAMG: Interpolation: max elements per
> row 0
> >                         HYPRE BoomerAMG: Number of levels of aggressive
> coarsening 0
> >                         HYPRE BoomerAMG: Number of paths for aggressive
> coarsening 1
> >                         HYPRE BoomerAMG: Maximum row sums 0.9
> >                         HYPRE BoomerAMG: Sweeps down         1
> >                         HYPRE BoomerAMG: Sweeps up           1
> >                         HYPRE BoomerAMG: Sweeps on coarse    1
> >                         HYPRE BoomerAMG: Relax down
> symmetric-SOR/Jacobi
> >                         HYPRE BoomerAMG: Relax up
> symmetric-SOR/Jacobi
> >                         HYPRE BoomerAMG: Relax on coarse
>  Gaussian-elimination
> >                         HYPRE BoomerAMG: Relax weight  (all)      1
> >                         HYPRE BoomerAMG: Outer relax weight (all) 1
> >                         HYPRE BoomerAMG: Using CF-relaxation
> >                         HYPRE BoomerAMG: Measure type        local
> >                         HYPRE BoomerAMG: Coarsen type        Falgout
> >                         HYPRE BoomerAMG: Interpolation type  classical
> >                       linear system matrix = precond matrix:
> >
> >
> >
> > Fande,
>
>
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