[petsc-users] DIVERGED_PCSETUP_FAILED

[Matthew Knepley]

On Wed, Feb 10, 2016 at 7:33 PM, Michele Rosso <mrosso at uci.edu> wrote:

> Hi,
>
> I encountered the following error while solving a symmetric positive
> defined system:
>
> Linear solve did not converge due to DIVERGED_PCSETUP_FAILED iterations 0
>                PCSETUP_FAILED due to SUBPC_ERROR
>
> This error appears only if I use the  optimized version of both petsc and
> my code ( compiler: gfortran, flags: -O3 ).
> It is weird since I am solving  a time-dependent problem and everything,
> i.e. results and convergence rate, are as expected until the above error
> shows up. If I run both petsc and my code in debug mode, everything goes
> smooth till the end of the simulation.
> However, if I reduce the ksp_rtol, even the debug run fails, after running
> as expected for a while, because of a KSP_DIVERGED_INDEFINITE_PC .
> The options I am using are:
>
> -ksp_type        cg
> -ksp_norm_type   unpreconditioned
> -ksp_rtol        1e-8
> -ksp_lag_norm
> -ksp_initial_guess_nonzero  yes
> -pc_type mg
> -pc_mg_galerkin
> -pc_mg_levels 4
> -mg_levels_ksp_type richardson
> -mg_coarse_ksp_constant_null_space
> -mg_coarse_pc_type lu
> -mg_coarse_pc_factor_mat_solver_package superlu_dist
> -options_left
>
> I attached a copy of ksp_view. I am currently using petsc-master (last
> updated yesterday).
> I would appreciate any suggestion on this matter.
>

I suspect you have a nonlinear PC. Can you send the output of -ksp_view?

   Matt


> Thanks,
> Michele
>
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-- 
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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