[petsc-users] MatMatSolve in sequential call

[Alexander Grayver]

On 21.08.2012 18:14, Hong Zhang wrote:
> Alexander :
>
> Testing your matrix A.dat 
> using petsc-3.3/src/ksp/ksp/examples/tutorials/ex10.c,
> I find that A is numerically singular:

Hong,

Sorry, but I forgot to mention that this is double complex symmetric 
matrix. Did you load and treat it like that?

> I'm convinced that matrix A is corrupted or obtained from an incorrect 
> numerical model.
> Also note, your matrix A has size of approx. 60k, which is too large 
> for sequential direct solver.

MUMPS takes only several minutes and 6 GB of memory to factorize it.
This factorization gives residual on the order of 10e-12 and solution is 
indeed correct.

Nevertheless, you're right, there is numerical null-space in this matrix 
since it comes
from the discretization of equation that contains curl curl operator, 
but practically this
case is not really the worst one.

>
> The error on MatMatSolve() when calling
> ' -pc_type cholesky -pc_factor_mat_solver_package mumps'
> is a bug in our petsc-mumps interface. I've pushed a fix to petsc-3.3
> http://petsc.cs.iit.edu/petsc/releases/petsc-3.3/rev/8badc49a596e
>
> Thanks for your report.

Thank you for the patch.

-- 
Regards,
Alexander

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