[petsc-users] speedup on KSPSetUp() using qmd reordering

[Matthew Knepley]

On Fri, May 7, 2010 at 2:06 PM, Pedro Torres <torres.pedrozpk at gmail.com>wrote:

> Hello,
>
> I have a sparse linear system, block dense, one block for each process, and
> solve with cg and block jacobi (ICC(0)) as preconditioners, with different
> reordering. During my tests I found quasi linear speed on kspsetup()
> and KSPSetUpOnBlocks() using 1wd,nd,rcm reorderings, but using qmd I get
> superlinear speedup. My CPU is a Xeon 5410.
>
> Is that possible or something is going wrong?, and if I want to explain
> that, what functions on this stage should I monitor??. I really
> appreciate any advice.
>

It is possible (but unlikely) that the ordering on a larger number of
processes creates a better
preconditioner, particularly because ICC(0) is so unpredictable. You can try
and separate
arithmetic efficiency from algorithmic efficiency by looking at the number
of iterates between these
runs.

   Matt


> Thanks in advance.
>
> --
> Pedro Torres
> GESAR/UERJ
> Rua Fonseca Teles 121, São Cristóvão
> Rio de Janeiro - Brasil
>



-- 
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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