[petsc-users] SNES convergence issue

[Jed Brown]

On Tue, May 17, 2011 at 01:25, Tian(ICT) <rongtian at ncic.ac.cn> wrote:

> pgfem -snes_monitor -snes_mf_operator -mat_mffd_type ds -ksp_type fgmres
> -ksp_monitor_true_residual -ksp_gmres_modifiedgramschmidt -ksp_rtol 1e-10 -pc_type
> none
>
> atol=1e-050, rtol=1e-008, stol=1e-008, maxit=50, maxf=10000
>   0 SNES Function norm 7.071067809722e+001
>   0 KSP preconditioned resid norm 7.071067809722e+001 true resid norm
> 7.071067809722e+001 ||Ae||/||Ax|| 1.000000000000e+000
>   1 KSP preconditioned resid norm 6.628127802131e+001 true resid norm
> 6.628127802131e+001 ||Ae||/||Ax|| 9.373588233757e-001
>   2 KSP preconditioned resid norm 6.060349268020e+001 true resid norm
> 8.023787055846e+001 ||Ae||/||Ax|| 1.134734847941e+000
>   3 KSP preconditioned resid norm 5.893436541308e+001 true resid norm
> 1.661766291099e+002 ||Ae||/||Ax|| 2.350092427079e+000
>

This is remarkably early loss of orthogonality. Does it do the same thing if
you remove -snes_mf_operator?

./pgfem -snes_monitor -ksp_type fgmres -ksp_monitor_true_residual
-ksp_gmres_modifiedgramschmidt -ksp_rtol 1e-10 -pc_type none

If so, add -ksp_view_binary and send the matrix (probably named
"binaryoutput") to petsc-maint at mcs.anl.gov .

./pgfem -snes_monitor -ksp_type fgmres -ksp_monitor_true_residual
-ksp_gmres_modifiedgramschmidt -ksp_rtol 1e-10 -pc_type none
-ksp_view_binary
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