In particular, intercommunicators
On 8/7/10, Aurélien Bouteiller <firstname.lastname@example.org
> You should consider reading about communicators in MPI.
> Aurelien Bouteiller, Ph.D.
> Innovative Computing Laboratory, The University of Tennessee.
> Envoyé de mon iPad
> Le Aug 7, 2010 à 1:05, Randolph Pullen <email@example.com
> écrit :
>> I seem to be having a problem with
>> 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
>> users mailing list
Sent from my mobile device
University of California, San Diego
users mailing firstname.lastname@example.org://www.open-mpi.org/mailman/listinfo.cgi/users