If the "subset of processes within a communicator" is reasonably stable you can do better by making an additional communicator containing only those processes and doing MPI_Bcast on this subset communicator. If the subset keeps changing then making the subset communicator may be too costly compared to the savings.
Dick Treumann - MPI Team/TCEM
IBM Systems & Technology Group
Dept 0lva / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601
Tele (845) 433-7846 Fax (845) 433-8363
owner-mpi-21@xxxxxxxxxxxxx wrote on 01/09/2008 05:51:36 PM:
>
> It will affect the performance of my code to fix it. The pattern I have
> here is that I'm sending the same buffer to a subset of the processes
> within a communicator. If this restriction is lifted, I can do that with
> a bunch of MPI_Isends to the various processes followed by a
> MPI_Waitall. To fix this code, I need to either clone the buffer N times
> (ouch!) or do N MPI_Sends in succession.
>