On Apr 6, 2010, at 6:04 PM, Oliver Geisler wrote: > Using netpipe and comparing tcp and mpi communication I get the > following results: > > TCP is much faster than MPI, approx. by factor 12 > e.g a packet size of 4096 bytes deliveres in > 97.11 usec with NPtcp and > 15338.98 usec with NPmpi > or > packet size 262kb > 0.05268801 sec NPtcp > 0.00254560 sec NPmpi
Well that's not good (for us). :-\ > Further our benchmark started with "--mca btl tcp,self" runs with short > communication times, even using kernel 2.6.33.1 I'm not sure what this statement means (^^). Can you explain? > Is there a way to see what type of communication is actually selected? If you "--mca btl tcp,self" is used, then TCP sockets are used for non-self communications (i.e., communications with peer MPI processes, regardless of location). > Can anybody imagine why shared memory leads to these problems? I'm not sure I understand this -- if "--mca btl tcp,self", shared memory is not used...? ....re-reading your email, I'm wondering: did you run the NPmpi process with "--mca btl tcp,sm,self" (or no --mca btl param)? That might explain some of my confusion, above. -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
