[petsc-users] MatMatSolve in sequential call

[Hong Zhang]

Alexander :
I need a simple code from you to reproduce the error for debugging.

If mumps' solver is activated, then you should get error (sequential and
parallel)
[0]PETSC ERROR: No support for this operation for this object type!
[0]PETSC ERROR: MatMatSolve_MUMPS() is not implemented yet!

If petsc's direct solver is activated, then you should not be able to run
it in parallel.

Please check ~petsc/src/mat/examples/tests/ex125.c
to see if you used same calling procedure as this example.
Note: I fixed a bug in this example and patched petsc-3.3.
The update copy of ex125.c is attached for your convenience.

Hong

On Mon, Aug 13, 2012 at 10:56 AM, Hong Zhang <hzhang at mcs.anl.gov> wrote:

> Alexander :
> petsc-mumps interface does not support MatMatSolve()
> see ~petsc/src/mat/impls/aij/mpi/mumps/mumps.c
> Likely MatMatSolve_Basic() is called which calls MatSolve()
> repeatedly, thus slow.
>
> In addition, MUMPS
> only supports centralized rhs. Petsc interface must scatter
> distributed rhs into a seqential rhs vector for MUMPS.
> If num of rhs is large, would be slow here as well.
>
> The error in your report likely is a bug in petsc. I'm investigating it
> and will let you know once it is fixed.
>
> Hong
>
> On 13.08.2012 17:23, Hong Zhang wrote:
>>
>>> Alexander :
>>> Hmm, isrow is a matrix ordering, likely a bug :-(
>>> Can you send us a stand-alone code that reproduces this error?
>>>
>>
>> Hong,
>>
>> I can try to pull it out, but this may be tricky.
>>
>>
>>  Do you use an external package for MatMatSolve()?
>>>
>>
>> Yes, MUMPS.
>> I use ksp with preonly.
>>
>> Originally I thought it will be faster to solve multiple problems using
>> MatMatSolve.
>> This turned out to be not true however, but the code is still like that.
>>
>> --
>> Regards,
>> Alexander
>>
>>
>
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