[Beowulf] Multidimensional FFTs

Konstantin Kudin konstantin_kudin at yahoo.com
Thu Mar 2 15:32:40 EST 2006


>>  Anyway, the "alltoall" can be a real killer. If you want to use
lots
>> of cpus with really small packets, go for something like Parastation
>> MPI ( http://www.parastation.com/ ).

>Konstantin,

> I take it that you're talking about only gigE? For which Parastation
> has a novel non-TCP driver. Another strategy would be to use a
> low-latency "ether-not" network.
>
>-- greg

 Greg,

 Thanks for the clarification! Indeed, I should have explicitly
mentioned that these are troubles with gigE. Unfortunately, with shared
use clusters faster interconnects do not seem to fly very well as far
as the purchasing decisions go, so one has to try to squeeze out as
much out of gigE as possible.

 By the way, any idea why gigE on Opterons with Broadcom chokes so
easily with different flavours of "alltoall" operation, such as if done
via "isend+irecv"? If functioning flawlessly, the scaling would have
been not too bad, but there seem to be issues of some sort ...

 Konstantin

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