[petsc-users] petsc4py: parallel matrix-vector multiplication

[Robert Speck]

Hi!

I would like to do a matrix-vector multiplication (besides using linear
solvers and so on) with petsc4py. I took the matrix from this example
(https://bitbucket.org/petsc/petsc4py/src/master/demo/kspsolve/petsc-mat.py)
and applied it to a PETSc Vector. All works well in serial, but in
parallel (in particular if ordering becomes relevant) the resulting
vector looks very different. Using the shell matrix of this example
(https://bitbucket.org/petsc/petsc4py/src/master/demo/poisson2d/poisson2d.py)
helps, but then I cannot use matrix-based preconditioners for KSP
directly (right?). I also tried using DMDA for creating vectors and
matrix and for taking care of their ordering (which seems to be my
problem here), but that did not help either.

So, my question is this: How do I do easy parallel matrix-vector
multiplication with petsc4py in a way that allows me to use parallel
linear solvers etc. later on? I want to deal with spatial decomposition
as little as possible. What data structures should I use? DMDA or
PETSc.Vec() and PETSc.Mat() or something else?

Thanks!
-Robert-

--
Dr. Robert Speck
Juelich Supercomputing Centre
Institute for Advanced Simulation
Forschungszentrum Juelich GmbH
52425 Juelich, Germany

Tel: +49 2461 61 1644
Fax: +49 2461 61 6656

Email:   r.speck at fz-juelich.de
Website: http://www.fz-juelich.de/ias/jsc/speck_r
PinT:    http://www.fz-juelich.de/ias/jsc/pint



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Prof. Dr. Sebastian M. Schmidt
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