[petsc-users] Flops pf MatMult is less than expected

[Junchao Zhang]

Because 2838 + 494 = 3332, I believe PETSc calculates flops of an inner
product as n-1, where n is the vector length.

On Fri, Dec 30, 2011 at 4:30 PM, Junchao Zhang <junchao.zhang at gmail.com>wrote:

> Hello,
>   I have a sparse matrix A. Its size is 494 x 494. It has 1666 nonzeros.
>   I call MatMult(A, x, y).  From the profiling result (got by
> -log_summary), I find MatMult's flops is 2838.
>   I think the flops should be nnz x 2 = 1666 x 2 = 3332.  I don't know how
> PETSc got this number (2838).
>   I also observed the phenomena with other matrices. It seems PETSc always
> give smaller flops.  Why?
>
>  Thank you!
> -- Junchao Zhang
>



-- 
Junchao Zhang
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111230/2a26b937/attachment.htm>