On Sat, 28 Sep 2002, [ISO-8859-1] Håvard Berland wrote:
> On Sat, 28 Sep 2002, Manish Chablani wrote:
> | Here is what LAM: MPI_Gatherv does.
> |
> | If rank != root then it does a MPI_Send and returns.
> | If rank == root, it does a MPI_Recv from each rank !=root serially.
>
> Is there any special reason not to do a non-blocking receive?
> Intuitively it should speed up the gathering process, but the speedup
> gained may be negligible?
MPI_Send and MPI_Recv are blocking, however for messages of size < buffer
size (64K for LAM/MPI) MPI_Send returns immediately without waiting for
corresponding MPI_Recv to be called. This is because of buffering. Check
out more about it in MPI documents at
http://www.mpi-forum.org/docs/mpi-11-html/node40.html#Node40
hope this helps,
Manish Chablani
------------------------------------------------------
Graduate Student, CS Department,
Indiana University.
Make today a LAM/MPI day !!!
http://www.lam-mpi.org/
------------------------------------------------------
>
> --
> Håvard Berland
> berland_at_[hidden]
> http://www.math.ntnu.no/~berland
>
>
>
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