[petsc-users] MatSolve_SeqAIJ_NaturalOrdering

[Jed Brown]

Randall Mackie <rlmackie862 at gmail.com> writes:

> After profiling our code, we have found that most of the time is spent in MatSolve_SeqAIJ_NaturalOrdering, which upon inspection is just doing simple forward and backward solves of already factored ILU matrices.
>
> We think that we should be able to see improvement by replacing these with optimized versions from Intel MKL (or other optimized BLAS).

Doing so would actually give up memory optimizations that are only in
PETSc.

http://hpc.sagepub.com/content/25/4/386 (also http://www.mcs.anl.gov/uploads/cels/papers/P1658.pdf)

Run with -log_summary and look at the rows for MatSolve versus MatMult.
Is the flop/s rate (last column) close?  If so, then you're already
getting a high fraction of memory bandwidth.
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