[petsc-users] jacobi before ilu with shifting

Barry Smith bsmith at mcs.anl.gov
Tue Jul 27 14:50:18 CDT 2010

Run with -help | grep shift to see what the exact name of the prefix/option is


On Jul 27, 2010, at 2:34 PM, SUN Chun wrote:

> Hi Petsc dev,
> I couldn't figure out this preconditioner setting... I want to do BJACOBI + ILU on each block with shifting, but before ILU I want to apply a diagonal scaling to my LHS. What I've been trying to do is:
> -pc_type bjacobi
> -sub_pc_type composite
> -sub_pc_composite_type multiplicative
> -sub_pc_composite_pcs jacobi,ilu
> then I don't know where to add -pc_factor_shift_positive_definite I've tried adding "sub_", "sub_pc_composite_" prefixes to that but non worked.
> I wonder if the whole idea of using composite is wrong. Where should I scale it? Where should I specify shifting?
> Thanks,
> Chun
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