[petsc-users] Is PCFactorSetZeroPivot() effective?

[Jozsef Bakosi]

Hello,

I have a mesh with very small cell sizes and in a Poisson equation CG solve
with ML preconditioner I get the following error:

[31]PETSC ERROR: --------------------- Error Message ------------------------------------
[31]PETSC ERROR: Detected zero pivot in LU factorization see
http://www.mcs.anl.gov/petsc/petsc-as/documentation/troubleshooting.html#ZeroPivot!
[31]PETSC ERROR: Zero pivot row 537 value 9.41111e-13 tolerance 1e-12!

I really would like PETSc to NOT treat matrix values lower than 1e-12 to
be zero, so I'm trying to set the zero pivot to a lower value with
PCFactorSetZeroPivot(), but I still get the same error message: as if
the function call would have no effect. I also tried setting the
zeropivot via PetscOptionsSetValue("-pc_factor_zeropivot", ...), but
still no luck.

Is there another way to set the zero pivot that I'm not aware of?

Is there a way to query the zero pivot value?

Thanks,
J
-- 
Jozsef Bakosi
Computational Physics Group (CCS-2)
MS T006, Los Alamos National Laboratory
Los Alamos, NM 87545, USA
email: jbakosi at lanl.gov
work: 505-663-5607
fax : 505-663-5504