(j3.2006) Lessons to be learned from HPF

Keith Bierman khbkhb
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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