Re: [petsc-dev] Questions around benchmarking and data loading with PETSc

[Mark Adams]

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> With a graph and a row-based algorithm, I would partition it using METIS
> or similar, then apply an RCM ordering within each block. This will give
> better locality of access to the vector x, which has been known (since at
> least the PETSc-FUN3D work in the late 90s) to be a major factor in SpMV
> performance.
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I can just add that we (at Berkeley) also looked at SpMV ordering in the
90s. Sivan Toledo has a nice paper on it and a grad student made a PhD
thesis in the topic ("Sparsity" package).
Anyway we found that if you did something reasonable, RCM, Metis,
performance was pretty similar (we used IBMs a lot also), and random
ordering was about 3x slower. FWIW.