[petsc-users] -log_summary for MatMult

[Matthew Knepley]

On Fri, Jun 15, 2012 at 8:31 PM, Alexander Grayver
<agrayver at gfz-potsdam.de>wrote:

> **
> Matt,
>
> According to that code:
>
> 486: *PetscErrorCode MatMult_MPIDense(Mat mat,Vec xx,Vec yy)*487: {488:   Mat_MPIDense   *mdn = (Mat_MPIDense*)mat->data;
> 492:  VecScatterBegin(mdn->Mvctx,xx,mdn->lvec,INSERT_VALUES,SCATTER_FORWARD);493:   VecScatterEnd(mdn->Mvctx,xx,mdn->lvec,INSERT_VALUES,SCATTER_FORWARD);494:   MatMult_SeqDense(mdn->A,mdn->lvec,yy);495:   return(0);496: }
>
>
> Each process has its own local copy of the whole vector vectors?
>

I am not sure what your point is. VecScatter is just an interface that has
many implementations. What
I am telling you is that the timing you sent only does reductions, no p2p
messages.

    Matt


> On 15.06.2012 14:27, Matthew Knepley wrote:
>
> On Fri, Jun 15, 2012 at 8:22 PM, Alexander Grayver <
> agrayver at gfz-potsdam.de> wrote:
>
>> Hello,
>>
>> When I call MatMult with MPIDENSE matrix in log summary I see:
>>
>> Event                Count      Time (sec)     Flops
>>         --- Global ---  --- Stage ---   Total
>>                   Max Ratio  Max     Ratio   Max  Ratio  Mess   Avg len
>> Reduct  %T %f %M %L %R  %T %f %M %L %R Mflop/s
>>
>> ------------------------------------------------------------------------------------------------------------------------
>> MatMult                1 1.0 9.5740e-01 1.5 8.19e+08 1.0 0.0e+00 0.0e+00
>> 1.0e+00  2 40  0  0  5   2 40  0  0  6  3419
>> MatMultTranspose       1 1.0 1.0793e+00 1.4 8.18e+08 1.0 0.0e+00 0.0e+00
>> 2.0e+00  2 40  0  0 11   2 40  0  0 11  3030
>>
>>
>> Why do number of messages and their length equal zero?
>
>
>  Because it uses only collectives.
>
>     MAtt
>
>
>>
>> --
>> Regards,
>> Alexander
>>
>>
>
>
>  --
> 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
>
>
>
> --
> Regards,
> Alexander
>
>


-- 
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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