[petsc-dev] FieldSplit and PCLSC

[Dave May]

Given the nullspace, I'd modify your options slightly
1)
  -fieldsplit_pressure_lsc_pc_type cholesky
or for something iterative
2)
-fieldsplit_pressure_lsc_pc_type icc
-fieldsplit_pressure_lsc_ksp_max_it 10

Kick out the mumps option.
You should not have to perform a direct solve on this system to obtain
good results.

Cheers,
  Dave


On 4 May 2011 15:34, Jed Brown <jed at 59a2.org> wrote:
> On Wed, May 4, 2011 at 15:29, <domenico.borzacchiello at univ-st-etienne.fr>
> wrote:
>>
>>                -fieldsplit_pressure_pc_type lsc \
>>                -fieldsplit_pressure_lsc_ksp_type fgmres \
>>                -fieldsplit_pressure_lsc_ksp_max_it 100 \
>>                -fieldsplit_pressure_lsc_ksp_constant_null_space \
>>                -fieldsplit_pressure_lsc_pc_type lu \
>>                -fieldsplit_pressure_lsc_pc_factor_mat_solver_package mumps
>
> Perhaps this direct solve is the problem? That operator is expected to be
> singular due to the constant null space so a direct solve is expected to
> produce nonsense.