[petsc-users] while solving the linear system with half billion unknowns on the super computer with 1020 cores, the preconditioner pcmg couldn't set up

[Matthew Knepley]

On Wed, Jan 9, 2013 at 12:45 PM, Fande Kong <fd.kong at siat.ac.cn> wrote:

> Hi all,
>
> I want to try to solve a problem with half billion unknowns with
> preconditioner pcmg (Of course, I have successfully provided the
> interpolation matrix and the coarse matrix).  When the size of the unknowns
> is 1e7 level, the solve work very well with 1020 cores on the super
> computer. But when the size of the unknowns increases to 1e8 level, the
> preconditioner setup stage break down. The following is my run script that
> I use to set the solver and the preconditioner.
>

You can see, I am sure, that this report is completely useless. What does
"the preconditioner setup stage break down" mean? Did it hang?
Did it crash? Did it output an error message that you did not send?

Also, you did not even send the configure.log or make.log. How do we have
any idea what you are doing?

    Matt


>  -pc_type mg  -ksp_type fgmres  -pc_mg_levels 2 -pc_mg_cycle_type v
> -pc_mg_type multiplicative  -mg_levels_1_ksp_type richardson
> -mg_levels_1_ksp_max_it 1 -mg_levels_1_pc_type asm
> -mg_levels_1_sub_ksp_type preonly -mg_levels_1_sub_pc_type ilu
> -mg_levels_1_sub_pc_factor_levels 1
> -mg_levels_1_sub_pc_factor_mat_ordering_type rcm -mg_coarse_ksp_type gmres
> -mg_coarse_ksp_rtol 0.1  -mg_coarse_ksp_max_it 2 -mg_coarse_pc_type asm
> -mg_coarse_sub_ksp_type preonly -mg_coarse_sub_pc_type ilu
> -mg_coarse_sub_pc_factor_levels 1
> -mg_coarse_sub_pc_factor_mat_ordering_type rcm -ksp_view
>
> My question is weather the linear system with half billion unknowns is too
> big to solve. Or are there some bugs in preconditioner pcmg?
>
> --
> Fande Kong
> ShenZhen Institutes of Advanced Technology
> Chinese Academy of Sciences
>



-- 
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
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