KSP solver efficiency

[Matthew Knepley]

On Fri, Feb 13, 2009 at 4:37 PM, Yixun Liu <enjoywm at cs.wm.edu> wrote:

> Hi,
> Assume  Ku=F is  a linear system assembled from element stiffness
> matrix. I want to use KSP to solve Ku=F. Assume the size of K is 100x100
> and the number of processors is 4.
> The question is does the efficiency of KSP depend on the structure of K?
> For example if each process owns 25 rows does the efficiency of the
> solver depend on the structure of K?


1) Strictly, yes it does.

2) Practically, not very much. You want to have at least a decent partition,
but
    after that the communication load is small since its a PDE, and scales
well.

3) Everything depends on the type of PDE. Krylov solvers will not work well
for
    everything, but for elliptic things they are good.

  Matt


>
> Thanks.
>
> 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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