matrix assembling time

[Ravi Kannan]

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?

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