Questions about Blas

[Matthew Knepley]

On Wed, Sep 16, 2009 at 1:09 PM, Rodrigo Araujo <rodrigowpa at gmail.com>wrote:

> Thanks for the answer,
>
> But I have another question.
>
> I am trying to multiply the matrices using 2 pcs, so I found the function
> MatMatMultNumeric_MPIDense_MPIDense, which probably could do this using the
> BLAS. My question is how the BLAS or the MPI splits the matrices to multiply
> them is separated pcs?
>

Same divisions as the matrices already have id they are MPIDENSE.

  Matt


> 2009/9/16 Hong Zhang <hzhang at mcs.anl.gov>
>
>>
>>  I am multiplying matrices using this line of code:
>>>
>>> ierr = MatMatMult(A, B, MAT_INITIAL_MATRIX, ((PetscReal) 2.0),
>>> &C);CHKERRQ(ierr);
>>>
>>> But I need to see the source code of the file which has this function,
>>> because I´d want to see how the functions from BLAS is being used. Is
>>> that
>>> possible? If yes, could somebody tell me how.
>>>
>>
>> We have implementations for different matrix data structures.
>> You can search 'MatMatMult_'
>> from petsc/src/ for all.
>> BLAS is used in MatMatMultNumeric_SeqDense_SeqDense()
>> in src/mat/impls/dense/seq/dense.c.
>> For sparse matrices, we do not use BLAS in MatMatMult().
>>
>> Hong
>>
>>
>>>
>>> --
>>> Rodrigo W. Pimentel Araujo
>>> Engenharia da Computação
>>> UFPE
>>>
>>
>
>
> --
> Rodrigo W. Pimentel Araujo
> Engenharia da Computação
> UFPE
>



-- 
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
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