[petsc-users] MatMatMult involving MPIAIJ and MATNEST

[Patrick Sanan]

Are you storing M^{-1} explicitly? In that case you could use MATCOMPOSITE
to define M^{-1}H and feed that to SLEPc's standard solver. If you only
have M explicitly, you could use MATSHELL to define your own operator which
applies M^{-1}H and use that with SLEPc's standard solver (though of course
SLEPc would be free to implement its generalized eigensolvers this way
and/or in better ways for certain problems - I am not enough of an expert
on that library to say more).

On Mon, May 11, 2015 at 7:12 PM, Bikash Kanungo <bikash at umich.edu> wrote:

> Hi Matthew,
>
> Yes SLEPc does allow me to solve a generalized eigenvalue problem. But the
> generalized solvers are not as robust as the standard eigenvalue solvers.
> That's the reason I want to use explicit MatMatMult so that I can use
> standard eigenvalue solvers.
>
> Thanks,
> Bikash
> On May 11, 2015 1:00 PM, "Matthew Knepley" <knepley at gmail.com> wrote:
>
>> On Mon, May 11, 2015 at 8:47 AM, Bikash Kanungo <bikash at umich.edu> wrote:
>>
>>> Hi Patrick,
>>>
>>> Thanks for the clarification. I want it to be an efficient operation.
>>> The idea is to convert a generalized eigenvalue problem (H*x = lamda*M*x)
>>> to a standard one (M^{-1}*H*x = lambda*x). The M^{-1} is of type MATNEST
>>> whereas H is MPIAIJ. In my problem M^{-1} is computed once whereas H
>>> changes every iteration. So performing low-level matrix multiplication or
>>> creating H as MATNEST and assembling it from its sub-matrices at every
>>> iteration sounds inefficient.
>>>
>>
>> You can solve these types of things with SLEPc without explicit MatMat.
>>
>>    Matt
>>
>>
>>> Regards,
>>> Bikash
>>>
>>> On Mon, May 11, 2015 at 9:21 AM, Patrick Sanan <patrick.sanan at gmail.com>
>>> wrote:
>>>
>>>> MatMatMult with MATNEST does not seem to be supported, based only on
>>>> the fact that there are no functions of the form MatMatMult_*_MatNest
>>>> defined with the MATNEST implementation :
>>>> http://www.mcs.anl.gov/petsc/petsc-current/src/mat/impls/nest/matnest.c.html
>>>>
>>>> Does this operation need to be efficient? (That is, are you forming
>>>> this matrix for debugging or experimental purposes, or with the intention
>>>> of using it within an efficient, scalable piece of code?). If not, it
>>>> should be possible to use lower-level matrix operations as defined by the
>>>> API to extract the appropriately-sized submatrices from A and (assuming
>>>> that MatMatMult is defined between MATMPIAIJ and the submatrices of your
>>>> Matnest), perform the matrix multiplications and additions "by hand" .
>>>>
>>>> On Mon, May 11, 2015 at 2:44 PM, Bikash Kanungo <bikash at umich.edu>
>>>> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> I have two matrices: A of type MPIAIJ and B of type MATNEST. Is there
>>>>> any way to perform A*B after B has been assembled from its sub-matrices?
>>>>>
>>>>> Thanks,
>>>>> Bikash
>>>>>
>>>>> --
>>>>> Bikash S. Kanungo
>>>>> PhD Student
>>>>> Computational Materials Physics Group
>>>>> Mechanical Engineering
>>>>> University of Michigan
>>>>>
>>>>>
>>>>
>>>
>>>
>>> --
>>> Bikash S. Kanungo
>>> PhD Student
>>> Computational Materials Physics Group
>>> Mechanical Engineering
>>> University of Michigan
>>>
>>>
>>
>>
>> --
>> What most experimenters take for granted before they begin their
>> experiments is infinitely more interesting than any results to which their
>> experiments lead.
>> -- Norbert Wiener
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20150511/6c2da707/attachment.html>