[petsc-users] Matrix dot product

[David Gross]

Hi Matt,
Noted for the naming convention.

Yes, it is a Newton method (see Pan, V. and Reif, J., Fast and Efficient
Parallel Solution of Dense Linear Systems, Computers Math. Applications.
Vol. 17, No. 11, pp. 1481-1491, 1989)

The dense matrix I have is repeatedly inverted while slowly changing such
that the previous inverse is a near perfect guess for the new inverse.

Regards,
Dave

On Thu, Sep 14, 2017 at 2:49 AM, Matthew Knepley <knepley at gmail.com> wrote:

> 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/
>
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