(j3.2006) Lessons to be learned from HPF
Tue Jul 24 12:52:05 EDT 2007
> 7. Single level of data parallelism too restrictive?
> [I'm not sure what this means but I assume co-arrays will suffer
> the same problem. If it means a flat image hierarchy, then co-arrays
> do have that problem. We are already seeing machines at LANL deeper
> memory and processor hierarchies (RoadRunner).]
I suspect that what this means is something like mixing MPI and
OpenMP .... little as some (myself included) like it, MPI has become
the de facto way to doing work on "clusters" of commodity processors
with (hopefully) fast links (e.g. myrinet or Infiniband). Now that
commodity processors are on a path to being nontrivial SMP machines
in their own right (let's say the doubling of cores continued at the
Moore's Law growth rate, assisted by packaging tricks like Intel's
two dies per chip ;>) using a model well suited to the shared memory,
etc. of the SMP enables good performance per "node" and managing
large ensembles of nodes is more tractable if one doesn't confuse the
onchip shared resources with the off chip ones.
I can hear the screaming from here, it's more complicated. It's too
low level, etc.
But I'm pretty sure it's what a class of consumer will strongly desire.
Keith H. Bierman khbkhb at gmail.com | AIM kbiermank
5430 Nassau Circle East |
Cherry Hills Village, CO 80113 | 303-997-2749
<speaking for myself*> Copyright 2007
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