[petsc-users] sor vs. asm + sor

[Tobin Isaac]

> >
> > What's the difference between "-pc_type sor -pc_sor_local_symmetric"
> > and "-pc_type asm -sub_pc_type sor -sub_pc_sor_local_symmetric"?
> >
> 
> The ASM version sticks a Krylov iteration in these by default.
> 
>    Matt
> 
> 

In this case the inner ksp is preonly so I think they ought to be the
same, but I figured out that the issue is a bug in
MatSOR_SeqAIJ_Inode, which I'll report to petsc-maint.

Thanks,
Toby

> > Specifically, this converges in 30 iterations:
> >
> > ./ex49 -mx 100 -my 100 -elas_ksp_view -elas_ksp_monitor -elas_ksp_type
> > cg -elas_pc_type gamg -elas_pc_gamg_verbose 10 -elas_pc_gamg_threshold
> > 0. -elas_mg_coarse_pc_type cholesky -elas_pc_mg_smoothup 1
> > -elas_pc_mg_smoothdown 1 -elas_mg_levels_ksp_type richardson
> > -elas_mg_levels_pc_type asm -elas_ml_levels_1_sub_pc_type sor
> >
> > While this iterates forever:
> >
> > ./ex49 -mx 100 -my 100 -elas_ksp_view -elas_ksp_monitor -elas_ksp_type
> > cg -elas_pc_type gamg -elas_pc_gamg_verbose 10 -elas_pc_gamg_threshold
> > 0. -elas_mg_coarse_pc_type cholesky -elas_pc_mg_smoothup 1
> > -elas_pc_mg_smoothdown 1 -elas_mg_levels_ksp_type richardson
> > -elas_mg_levels_pc_type sor
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 198 bytes
Desc: Digital signature
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120905/f23a593a/attachment-0001.pgp>