On Nov 8, 2004, at 4:40 PM, Mike Arnold wrote:
> Will other posted communications progress during a call to
> MPI_Barrier()?
It depends. The MPI standard doesn't say, which means that it is legal
if it doesn't, and it's legal if it does.
In LAM, if you use the lam_basic or smp coll modules, then yes, other
p2p requests may progress during the call to MPI_Barrier. This is
because the lam_basic and smp coll modules are implemented using p2p
calls themselves (e.g., MPI_SEND, MPI_RECV, etc.).
But if you're using the shmem coll module (i.e., if all the processes
on the communicator are on the same node), then shared memory
algorithms are used and MPI p2p calls are not used. This means that
the p2p progression engine is not invoked, and other p2p requests are
not progressed.
Hope that helps.
--
{+} Jeff Squyres
{+} jsquyres_at_[hidden]
{+} http://www.lam-mpi.org/
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