[Beowulf] Re: Re: Home beowulf - NIC latencies
rossen at VerariSoft.Com
Tue Feb 15 06:34:39 PST 2005
> A last remark. I really think that the argument of using the same
> swiss-army-knive MPI implementation such as ScaMPI or Intel MPI or even
> MPI/Pro to infere interconnect characteristics is even worse that
> looking at latency and bandwidth alone. These implementations are never
> going to be designed to use all hardware efficiently, their design is
> either historic (Scali used to provided software for SCI alone) or
> politicaly motivated (Intel is using uDapl, hummm, wonder why), or both.
> They are by-products of the MPI forum failure to make the Standard
> practical (compatible ABI).
Patrick, this is quite a broad statement. 4 years ago we had a paper
arguing that MPI's written to support many different interconnects and
messaging technologies through internal portability layers were probably
sub-optimal for at least some of the interconnects. Most of the reasons
are obvious. At the time we were dealing with Portals, LAPI, and GM. You
can easily see why having an internal portability layer for these
interfaces does not seem to easily match the semantics of either one of
them. We probably did something in our design to reflect this.
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