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Technology Stocks : Silicon Graphics, Inc. (SGI)
SGI 90.20-0.7%Dec 4 3:59 PM EST
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To: Jerry Whlan who wrote (3645)11/24/1997 6:08:00 AM
From: Alexis Cousein   of 14451
 
>The bonus of doing it for a system like IBM's
>was that using MPI (a message passing interface for distributed
>memory systems) was extremely portable, all high-performance vendors >support MPI so it is not a big deal to move your code from that Cray >to the IBM and a lot of the tuning you did for MPI on the
>Cray is just as useful on the IBM or the Origin.

1)
You'll see there is a very efficient MPI library on the Origin as well, *and* it runs better than on an SP2 on a very significant class of problems (not *all* problems can be domain-decomposed to make the inter-node communication overhead negligible) because of the low-latency, high-bandwidth interconnect.

2)
You don't have to use MPI if you don't want to. Compare the number of commercial packages for finite elements, chemistry etc. for SMP and for MPI-type programming, and you'll see.

And don't try to put all the cc-NUMA machines into one bucket. The effort some SGI benchmarkers I know had into 'porting' an SMP application and 'tune it' to a 64P machine was putting

setenv _DSM_ROUND_ROBIN

to distribute the memory evenly over the nodes, that's all. The latency of less than 1 microsecond even to the *other* side of the machine was negligible in this case, and bandwidth all that counts. Not so if you incur a large inter-node latency, as on other cc-NUMA architectures.
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