[petsc-users] When is it better to use MUMPS?

[Hong Zhang]

Jim,

    In my view, the intent of parallel computing is sovling large system.
> As you said, MUMPS is mainly used in
>

" the intent" does not automatically become the reality.
All parallel direct solvers are intended to solve ill-conditioned problems
as large as possible.
But the algorithms (full matrix factorization) consume large memories and
inter-processor
communications. Unless your matrix has special data structure, the direct
solvers cannot be scalable
in general.

 small problems. So are they contradictory. Or, is the "Small problems and
> moderate-size 2D problems" just relative,
> compared with the large system?
>
Yes.

Hong

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> At 2012-10-30 23:47:59,"Jed Brown" <jedbrown at mcs.anl.gov> wrote:
>
> Simple: it's better when it's faster. Small problems and moderate-size 2D
> problems often work well with direct solvers.
> On Oct 30, 2012 8:29 AM, "w_ang_temp" <w_ang_temp at 163.com> wrote:
>
>>  Hello,
>>     As is know, MUMPS is based on a direct method. When the system is
>> big, the parallel direct solver is
>> not effective compared with the iterative solver. So when is it better to
>> use MUMPS?
>>     Thanks.
>>                                          Jim
>>
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