On Dec 9, 2008, at 9:49 PM, Brock Palen wrote:
> Is OpenMPI using Multicast for things like MPI_Bcast() ?
Not today. There have been some experiments with it, but nothing yet.
> Some simple tests of really old versions (1.0.2) showed binary tree
> type performance, while latter versions gave me the same run time no
> matter how many CPU's I used.
> Thus this lead me to believe that something like multicast is in
> use. Is it?
That's an interesting result. It should depend on factors such as the
number of MPI processes you use, the size of the message, the layout
on the hosts/network, etc.