In particular, intercommunicators On 8/7/10, Aurélien Bouteiller <boute...@eecs.utk.edu> wrote: > You should consider reading about communicators in MPI. > > Aurelien > -- > Aurelien Bouteiller, Ph.D. > Innovative Computing Laboratory, The University of Tennessee. > > Envoyé de mon iPad > > Le Aug 7, 2010 à 1:05, Randolph Pullen <randolph_pul...@yahoo.com.au> a > écrit : > >> I seem to be having a problem with MPI_Bcast. >> My massive I/O intensive data movement program must broadcast from n to n >> nodes. My problem starts because I require 2 processes per node, a sender >> and a receiver and I have implemented these using MPI processes rather >> than tackle the complexities of threads on MPI. >> >> Consequently, broadcast and calls like alltoall are not completely >> helpful. The dataset is huge and each node must end up with a complete >> copy built by the large number of contributing broadcasts from the sending >> nodes. Network efficiency and run time are paramount. >> >> As I don’t want to needlessly broadcast all this data to the sending nodes >> and I have a perfectly good MPI program that distributes globally from a >> single node (1 to N), I took the unusual decision to start N copies of >> this program by spawning the MPI system from the PVM system in an effort >> to get my N to N concurrent transfers. >> >> It seems that the broadcasts running on concurrent MPI environments >> collide and cause all but the first process to hang waiting for their >> broadcasts. This theory seems to be confirmed by introducing a sleep of >> n-1 seconds before the first MPI_Bcast call on each node, which results >> in the code working perfectly. (total run time 55 seconds, 3 nodes, >> standard TCP stack) >> >> My guess is that unlike PVM, OpenMPI implements broadcasts with broadcasts >> rather than multicasts. Can someone confirm this? Is this a bug? >> >> Is there any multicast or N to N broadcast where sender processes can >> avoid participating when they don’t need to? >> >> Thanks in advance >> Randolph >> >> >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/users >
-- Sent from my mobile device David Zhang University of California, San Diego
