[Beowulf] Re: Re: Home beowulf - NIC latencies

Greg Lindahl lindahl at pathscale.com
Wed Feb 16 19:04:55 EST 2005


On Wed, Feb 16, 2005 at 03:03:16PM -0500, Robert G. Brown wrote:

> Optimizing any particular MPI (or PVM) command for either extreme is
> then like robbing Peter to pay Paul, when Peter and Paul are a single
> bicephalic individual that has to pay protection money to the mob for
> every theft transaction (oh how I just LOVE to fold, spindle and
> mutilate metaphors).  

Um, most MPI implementations have at least 3 algorithms, for short,
long, and very long messages. So are they all breaking your rule?

It's *unoptimizing* some of the cases that's at question. Most MPIs
unoptimize compute/communication overlap with long messages, because
it's hard work to get that right without hurting all short messages.

-- greg

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