[petsc-users] GAMG PC dependence on right-hand side

[John Mousel]

I'm trying to reuse the PC constructed by GAMG during a sub-iterative
procedure where KSPSolve is called with the same matrix repeatedly. The
right-hand side changes during the sub-iteration. I've been attempting to
use SAME_PRECONDITIONER for nit = 2..., but this seems to lead to very
different results than using DIFFERENT_PRECONDITIONER each sub-iteration.
I'm using the following options:

-pres_ksp_type preonly -pres_pc_type redistribute
-pres_redistribute_ksp_type bcgsl -pres_redistribute_pc_type gamg
-pres_redistribute_pc_gamg_threshold 0.01
-pres_redistribute_mg_levels_ksp_type richardson
-pres_redistribute_mg_levels_pc_type sor
-pres_redistribute_mg_coarse_ksp_type richardson
-pres_redistribute_mg_coarse_pc_type sor
-pres_redistribute_mg_coarse_pc_sor_its 5 -pres_redistribute_pc_gamg_type
agg -pres_redistribute_pc_gamg_agg_nsmooths 1
-pres_redistribute_pc_gamg_sym_graph true
-pres_redistribute_ksp_initial_guess_nonzero 0

Is there a dependence on the right-hand side in GAMG somewhere?


John
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