[petsc-users] questions on hypre preconditioner

[Barry Smith]

> 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.

> 
> (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.





> 
>  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,