matrix assembling time

[Matthew Knepley]

On Fri, Mar 13, 2009 at 12:48 PM, Ravi Kannan <rxk at cfdrc.com> wrote:

> Hi,
>    This is Ravi Kannan from CFD Research Corporation. One basic question on
> the ordering of linear solvers in PETSc: If my A matrix (in AX=B) is a
> sparse matrix and the bandwidth of A (i.e. the distance between non zero
> elements) is high, does PETSc reorder the matrix/matrix-equations so as to
> solve more efficiently. If yes, is there any specific command to do the
> above?


You can reorder the matrix using the MatOrdering class.

  Matt


>
> Thanks
> Ravi
>
>
>
> -----Original Message-----
> From: petsc-users-bounces at mcs.anl.gov
> [mailto:petsc-users-bounces at mcs.anl.gov]On Behalf Of Yixun Liu
> Sent: Friday, March 06, 2009 12:50 PM
> To: PETSC
> Subject: matrix assembling time
>
>
> Hi,
> Using PETSc the assembling time for a mesh with 6000 vertices  is about
> 14 second parallelized on 4 processors, but another sequential program
> based on gmm lib is about 0.6 second. PETSc's solver is much faster than
> gmm, but I don't know why its assembling is so slow although I have
> preallocate an enough space for the matrix.
>
> MatMPIAIJSetPreallocation(sparseMeshMechanicalStiffnessMatrix, 1000,
> PETSC_NULL, 1000, PETSC_NULL);
>
> Yixun
>
>
>


-- 
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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