[petsc-users] Matrix dot product

[Matthew Knepley]

On Wed, Sep 13, 2017 at 6:14 PM, David Gross <davegwebb10 at gmail.com> wrote:

> Hi Matt,
> Thank you for getting back to me. Your answer confirms what I thought in
> terms of existing functionality. I think it shouldn't be too hard to make a
> copy of MatAXPY to MatAXY where it performs Xij = A*Xij*Yij (or without the
> A). I could then do the MatNorm of the resulting matrix to get what I need.
>
> Is a MatAXY function desirable as a source contribution?
>

Yes. I would prefer calling it MatPointwiseMult, since you can see it as
VecPointwiseMult on a Vec obtained
from forgetting the linear operator structure of the matrix (forgetful
functor).


> I am hoping to use PETSc for performing basic vector and matrix operations
> on dense matrices and 1D vectors. The main uses are matmult, matmatmult and
> matrix additions and scaling. The application is for implementing a
> parallel version on an existing Pan-Reif matrix inversion algorithm.
>

Is this Newton's method on the vector space of matrices?

  Thanks,

    Matt


> The choice of using PETSc is mostly due to us already using it in the same
> program to solve sparse matrices (with MUMPS) with the goal of avoiding
> adding yet another package (ex ScaLAPACK/PBLAS) into the code even if other
> packages may be more directly oriented towards my application.
>
> Regards,
> Dave
>
>
>
> On Mon, Sep 11, 2017 at 2:19 AM, Matthew Knepley <knepley at gmail.com>
> wrote:
>
>> On Sun, Sep 10, 2017 at 5:51 PM, David Gross <davegwebb10 at gmail.com>
>> wrote:
>>
>>> Hello,
>>> I was wondering if there was a matrix equivalent to the vecDot function
>>> (Frobenius inner product)? As far as I can tell the closest thing is
>>> MatNorm with NORM_FROBENIUS, but obviously this is acting on only one
>>> matrix.
>>>
>>> If there is not a built in function, what is the best way to compute
>>> this? I am working fortran90.
>>>
>>
>> We do not have this. However, it would be trivial to add since we have
>>
>>   http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpage
>> s/Mat/MatAXPY.html
>>
>> since you just replace + with * in our code. You could argue that we
>> should have written for
>> a general ring, but C makes this cumbersome. Do you think you could make
>> the change?
>>
>> What are you using this for?
>>
>>   Thanks,
>>
>>      Matt
>>
>>
>>> Regards,
>>> Dave
>>>
>>
>>
>>
>> --
>> 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
>>
>> http://www.caam.rice.edu/~mk51/
>>
>
>


-- 
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

http://www.caam.rice.edu/~mk51/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20170913/ecd3fa7f/attachment.html>