i'm new on this list and started using OpenMPI for
my parallel jobs. first step was to measure the latency for blocking
communication functions. now my first question: is it possible
that ordained communication pairs will be optimized?
latency for special processnumbers is nearly
25% smaller, e.g. for process 1,2,4,8,16,32,64... (every computer scientist
should see the pattern ;-)). it doesn't matter from which process i send the
message if the receiver is one of these processes i have top latency
values. it's not possible that this effect comes through the network because
communication from proc5 to proc32 e.g. is faster than communication from proc32
to proc5. i've tried it with OpenMPI for Intel
1.1.4 and 1.2.2 and OpenMPI for PGI 1.2.2. always the same results. now i think
it must be a kind of optimization. if it's so i would like to know it because
then i have an explanation ;-).
thx and regards,