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

[Barry Smith]

   Send the output from -log_summary to petsc-maint at mcs.anl.gov on the various approaches and we'll comment on it.

   Barry

On May 7, 2010, at 2:32 PM, Pedro Torres wrote:

> 
> 
> 2010/5/7 Matthew Knepley <knepley at gmail.com>
> 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.
> Thanks for a swift response. I found that given an ordering, the number of iterations is almost uniform,with just a little increase, but 1wd have the minimun numbers of iterations. May be I should look
> in the ratio of cache miss of MatCholeskyFactorNumeric to explain this behavior, rigth?.
> Thanks a lot!
>    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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