[petsc-users] Using factored complex matrices from MUMPS as a preconditioner in PETSC

[Evan Um]

Hi Hong,

Thanks for your help. I am testing if I can use MUMPS block low rank
factors as a preconditioner for QMR in MUMPS framework. I would like to ask
one more question. STRUMPACK (
http://portal.nersc.gov/project/sparse/strumpack/) also supports low rank
approximation. Can PETSC also allow users to use the approximate factors as
a preconditioner in PETSC-QMR?

Best,
Evan


On Tue, Oct 3, 2017 at 8:34 AM, Hong <hzhang at mcs.anl.gov> wrote:

> Evan,
> ICNTL(35) and CNTL(7) are added to petsc-mumps interface in branch
> hzhang/update-mumps-5.1.1-cntl
>
> You may give it a try. Once it passes our regression tests, I'll merge it
> to petsc master branch.
>
> Hong
>
>
> On Sun, Sep 24, 2017 at 8:08 PM, Hong <hzhang at mcs.anl.gov> wrote:
>
>> I'll check it.
>> Hong
>>
>> On Sun, Sep 24, 2017 at 3:42 PM, Evan Um <evanum at gmail.com> wrote:
>>
>>> Hi Barry,
>>>
>>> Thanks for your comments. To activate block low rank (BLR) approximation
>>> in MUMPS version 5.1.1, a user needs to turn on the functionality (i.e.
>>> ICNTL(35)=1) and specify the tolerance value (e.g. CNTL(7)=1e-4). In PETSC,
>>> I think that we can set up ICNTL and CNTL parameters for MUMPS. I was
>>> wondering if we can still use BLR approximation for a preconditioner for
>>> Krylov solvers.
>>>
>>> Best,
>>> Evan
>>>
>>>
>>> On Sat, Sep 23, 2017 at 6:45 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>>
>>>>
>>>> > On Sep 23, 2017, at 8:38 PM, Evan Um <evanum at gmail.com> wrote:
>>>> >
>>>> > Dear PETSC Users,
>>>> >
>>>> > My system matrix comes from finite element modeling and is complex
>>>> and unstructured. Its typical size is a few millions-by a few millions. I
>>>> wondering if I can use MUMPS parallel direct solver as a preconditioner in
>>>> PETSC. For example, I want to pass factored matrices to Krylov iterative
>>>> solvers such as QMR. Is there any PETSC+MUMPS example code for the purpose?
>>>>
>>>>   You don't pass factored matrices you just pass the original matrix
>>>> and use -pc_type lu -pc_factor_mat_solver_package mumps
>>>>
>>>> > Can PETSC call the latest MUMPS that supports block low rank
>>>> approximation?
>>>>
>>>>   No, send us info on it and we'll see if we can add an interface
>>>>
>>>>
>>>> >
>>>> > In advance, thank you very much for your comments.
>>>> >
>>>> > Best,
>>>> > Evan
>>>> >
>>>> >
>>>> >
>>>> >
>>>> >
>>>>
>>>>
>>>
>>
>
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