[petsc-users] Method and PC for indefinite FE-problem

[Mårten Ullberg]

Dear all,

I am currently working on some large soil-structure interaction
problems and therefor I have a finite element discretization that is
going be solved in the frequency domain. This results in a symmetric,
but indefinite matrix. I have not been able to find a proper method to
use when solving it with PETSc.

I was wondering if you guys have any recommendation on what to try,
both concerning method but especially the PC? Is it recommended to use
a composite PC for indefinite problems? I have tried the methods (such
as MINRES, SYMMLQ) that are suggested for indefinite problems with no
success. For small problems, GMRES+ASM+LU works fine, but for larger
the memory consumption goes off the chart. I've also been able to use
MUMPS but find it both memory and time consuming.

I apologize for my lack of knowledge about iterative methods,

Best regards,
Mårten