[petsc-users] Question concerning ilu and bcgs
Karl Rupp
rupp at iue.tuwien.ac.at
Wed Feb 18 02:30:48 CST 2015
Hi,
> I have a matrix system Ax = b, A is of type MatSeqAIJ or MatMPIAIJ,
> depending on the number of cores.
>
> I try to solve this problem by pc_type ilu and ksp_type bcgs, it does
> not converge. The options I specify are:
>
> -pc_type hypre -pc_hypre_type pilut -pc_hypre_pilut_maxiter 1000
> -pc_hypre_pilut_tol 1e-3 -ksp_type b\
>
> cgs -ksp_rtol 1e-10 -ksp_max_it 1000 -ksp_monitor_short
> -ksp_converged_reason
>
>
> The first a few lines of the output are:
>
> 0 KSP Residual norm 1404.62
>
> 1 KSP Residual norm 88.9068
>
> 2 KSP Residual norm 64.73
>
> 3 KSP Residual norm 71.0224
>
> 4 KSP Residual norm 69.5044
>
> 5 KSP Residual norm 455.458
>
> 6 KSP Residual norm 174.876
>
> 7 KSP Residual norm 183.031
>
> 8 KSP Residual norm 650.675
>
> 9 KSP Residual norm 79.2441
>
> 10 KSP Residual norm 84.1985
>
>
> This clearly indicates non-convergence.
please send the full output. Where does your matrix A come from (i.e.
which problem are you trying to solve)? Is this a serial run? ILU may
fail depending on the particular choice of tolerance, pivoting, etc., so
we need more information to suggest better options. Does the default
GMRES+ILU0 work?
Best regards,
Karli
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