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

Patrick Geoffray patrick at myri.com
Wed Feb 16 03:17:02 EST 2005


Keith D. Underwood wrote:
>>c) ban of the ANY_SENDER wildcard: a world of optimization goes away 
>>with this convenience.
> 
> 
> Um, our apps guys say this is more than a convenience.  Apparently,
> sometimes you don't exactly know who you are going to receive from. 
> Would you rather them post receives from 4000 nodes and cancel the ones
> that don't send to that node after a while?

No, I would not post any receives and let them come unexpected, sing 
MPI_Probe() to post a matching receive when something show up. It leaves 
the MPI implementation a way to move most of the matching to the send 
side for most of the messages and, if the receive is posted early 
enough, remove the need for host CPU on the receive side when the 
application is potentially computing.

And you remind me, I would ban MPI_Cancel also. It should have been the 
item #1 :-)

Patrick
-- 

Patrick Geoffray
Myricom, Inc.
http://www.myri.com
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