[petsc-users] MatMatMult involving MPIAIJ and MATNEST

[Bikash Kanungo]

Cool. I guess I'll have to profile both ways: MATCOMPOSITE and explicit
MatMat.
On May 11, 2015 1:47 PM, "Patrick Sanan" <patrick.sanan at gmail.com> wrote:

> I think that depends on how sparse M^{-1} and H are.
>
> On Mon, May 11, 2015 at 7:41 PM, Bikash Kanungo <bikash at umich.edu> wrote:
>
>> Hi Patrick,
>>
>> I have M^{-1} computed explicitly and stored as MATNEST. Providing
>> MATCOMPOSITE of M^{-1}H to SLEPc standard eigenvalue solvers seems an
>> option. Does it has any additional cost over explicitly building M^{-1}H
>> (assuming I have a way to do so) and then providing it to standard
>> eigenvalue solvers?
>>
>> Thanks,
>>
>> Bikash
>>
>> On Mon, May 11, 2015 at 1:37 PM, Bikash Kanungo <bikash at umich.edu> wrote:
>>
>>> Hi Patrick,
>>>
>>> I have M^{-1} computed explicitly and stored as MATNEST. Providing
>>> MATCOMPOSITE of M^{-1}H to SLEPc standard eigenvalue solvers seems an
>>> option. Does it has any additional cost of explicitly building
>>> On May 11, 2015 1:30 PM, "Patrick Sanan" <patrick.sanan at gmail.com>
>>> wrote:
>>>
>>>> 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
>>>>>>
>>>>>
>>>>
>>
>>
>> --
>> Bikash S. Kanungo
>> PhD Student
>> Computational Materials Physics Group
>> Mechanical Engineering
>> University of Michigan
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20150511/676ae57d/attachment-0001.html>