On Thu, Mar 02, 2006 at 12:32:40PM -0800, Konstantin Kudin wrote: > 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 ...
Congestion. Ethernet switches are the guilty party, not the Broadcom nics. MPI can makes this better by avoiding, for example, having everyone send first to process 0, then to 1, etc. So MPICH, for example, has rank R send to R+1, R+2, etc. -- greg _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
