[petsc-users] Symmetric MPIAIJ matrix

[Bikash Kanungo]

Aha ! That should do the trick. Thanks a lot.

On Tue, Jul 7, 2015 at 4:54 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Tue, Jul 7, 2015 at 3:52 PM, Bikash Kanungo <bikash at umich.edu> wrote:
>
>> Hi Matthew,
>>
>> I couldn't follow your reply. It seems a bit unrelated to my query.
>>
>
> Your matrix actually looks like M = A + v^T v, where A is sparse and v is
> a small collection of vectors. It is better
> is you handle it this way than putting a dense row into a traditional
> sparse matrix.
>
>    Matt
>
>
>>
>> Thanks,
>> Bikash
>>
>> On Tue, Jul 7, 2015 at 4:42 PM, Matthew Knepley <knepley at gmail.com>
>> wrote:
>>
>>> On Tue, Jul 7, 2015 at 3:36 PM, Bikash Kanungo <bikash at umich.edu> wrote:
>>>
>>>> Hi Matthew,
>>>>
>>>> The entries to the last few rows of my matrix has non-local
>>>> contributions from a large number of processors. Since the matrix is
>>>> symmetric, I need not set the non-local entries in the last few rows as
>>>> they are equal to their transpose entries, which on the other hand are
>>>> stored as local entries in their respective processors.
>>>>
>>>
>>> This is really a sparse matrix with a low rank update. It is much easier
>>> to handle it this way. There are explicit formulae for the inverse
>>> in terms of the inverse of the two parts (Sherman-Morrison-Woodbury),
>>> and other operations can be similarly simplified. We might not
>>> have all the support now, but pressing forward on this front is likely
>>> to be much more fruitful.
>>>
>>>   Thanks,
>>>
>>>     Matt
>>>
>>>
>>>> Thanks,
>>>> Bikash
>>>>
>>>> On Tue, Jul 7, 2015 at 4:25 PM, Matthew Knepley <knepley at gmail.com>
>>>> wrote:
>>>>
>>>>> On Tue, Jul 7, 2015 at 3:22 PM, Bikash Kanungo <bikash at umich.edu>
>>>>> wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> Is there a way to ignore the lower (or upper) triangular entries in
>>>>>> an MATMPIAIJ matrix when I know my matrix is symmetric? I can see a
>>>>>> MAT_SYMMETRIC option in MatSetOption, but I don't think it ignores any
>>>>>> lower (or upper) triangular entry.
>>>>>>
>>>>>
>>>>> Why do you want this?
>>>>>
>>>>>
>>>>>> I cannot use MATMPISBAIJ due to MatMatMult incompatibility with
>>>>>> MATMPIAIJ.
>>>>>>
>>>>>
>>>>> This is the only way. MatMatMult() is quite complex and there is no
>>>>> real advantage to ignoring
>>>>> the entries, so we have not implemented it here.
>>>>>
>>>>>   Matt
>>>>>
>>>>>
>>>>>> Thanks,
>>>>>> Bikash
>>>>>>
>>>>>> --
>>>>>> 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
>>>>
>>>>
>>>
>>>
>>> --
>>> 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
>>
>>
>
>
> --
> 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
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