On Tue, 2009-03-24 at 07:03 -0800, Eugene Loh wrote: > > Perhaps there is a better way of accomplishing the same thing however, > > MPI_Barrier syncronises all processes so is potentially a lot more > > heavyweight than it needs to be, in this example you only need to > > syncronise with your neighbours so it might be quicker to use a > > send/receive for each of your neighbours containing a true/false value > > rather than to rely on the existence of a message or not. i.e. the > > barrier is needed because you don't know how many messages there are, > > it may well be quicker to have a fixed number of point to point > > messages rather than a extra global synchronisation. The added > > advantage of doing it this way would be you could remove the Probe as > > well. > > I'm not sure I understand this suggestion, so I'll say it the way I > understand it. Would it be possible for each process to send an "all > done" message to each of its neighbors? Conversely, each process would > poll its neighbors for messages, either processing graph operations or > collecting "all done" messages depending on whether the message > indicates a graph operation or signals "all done".
Exactly, that way you have a defined number of messages which can be calculated locally for each process and hence there is no need to use Probe and you can get rid of the MPI_Barrier call. Ashley Pittman.
