Matrix solvers?

Matthew Knepley knepley at
Wed Mar 1 14:09:10 CST 2006

billy at writes:

> Hi,
> I am using a single computer and several processes. I am using KSPGMRES for
> solving matrices. When I use increase the number of processes I have problems
> solving the matrix. Is there a more optimized solver for parallel processing?

  Yes, you should investigate the DMMG examples. This is geometric multigrid
for structured meshes. Since you have an unstructured mesh, it is more complicated.
We are working on this,but it is not ready yet. However, you can try using ASM
which should scale better.

> When I update ghost cells information with VecGhostUpdateBegin/End() do I need
> to call MPI_Barrier to assure that all ghost information is updated before
> proceeding or is this already done by the VecGhostUpdateBegin/End()?

  No, that is in the End() call.

"Failure has a thousand explanations. Success doesn't need one" -- Sir Alec Guiness

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