On Sep 10, 2010, at 10:46 PM, xingqiu yuan wrote: > Hi > > I found that use of mpi_allreduce to calculate the global maximum and > minimum takes very long time, any better alternatives to calculate the > global maximum/minimum values?
If only the rank 0 process needs to know the global max and min you can use MPI_Reduce() rather than MPI_Reduceall() which will substantially reduce the communication time. The difference is that with MPI_Reduce() the result of the reduction is not communicated back to the other ranks. charlie _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
