[petsc-users] Exploiting symmetry with direct solvers

[David Knezevic]

On Wed, Apr 8, 2015 at 9:28 PM, Hong <hzhang at mcs.anl.gov> wrote:

> David ,
>
>> I'm curious about how to do a symmetric LDL^T factorization (instead of
>> LU) with MUMPS and SuperLU. Based on this example:
>>
>>
>> http://www.mcs.anl.gov/petsc/petsc-3.4/src/ksp/ksp/examples/tutorials/ex52.c.html
>>
>> my understanding is as follows:
>>
>> - With MUMPS I gather that we need to specify:
>>
>> MatSetOption(A,MAT_SPD,PETSC_TRUE);
>> PCSetType(pc,PCCHOLESKY);
>>
>> I guess "-pc_type cholesky" on the command line is equivalent to the
>> PCSetType call, right? Is specifying MAT_SPD required in order for MUMPS to
>> do an LDL^T factorization?
>>
> Mumps supports Cholesky factorization for symmetric, and symmetric+spd
> matrices.  You may consult mumps user manual.
>


OK, thanks. But I was also wondering about the PETSc interface to MUMPS.

I consulted the MUMPS manual, but it just says that you need to specify
"SYM=1" in order to get an LDL^T factorization. I gather that if we set
MatSetOption(A,MAT_SPD,PETSC_TRUE); in PETSc then that will tell MUMPS to
use SYM=1, right?

Thanks,
David
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