mccalpin@perelandra.cms.udel.edu (John D. McCalpin) -
I have a question on your bandwidth-limited Mflop benchmarks.
Your benchmark measures bandwidth to global memory, without allowing
cache-based processors to get benefits from reusing data in local
memory. I understand that this is an accurate reflection of many large
dense matrix applications.
Yet you apparently allow the CM-2 to access local memory.
Why not measure the saxpy in the a(i) = a(i) + scalar*b(i) format?
This configuration of saxpy is frequently used. This would remove the
penalty on cached machines' pre-read on a(i). Alternately, why not
insist that at least one of a, b, or c be on a different processor in
the CM-2? This would seem to be true when using saxpy for matrix
multiply or Gaussian elimination.
Thank you for your attention and response.
- Bob Greiner, Motorola Computer Group, bobg@phx.mcd.mot.com
Personal opinion only
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