[MPICH] Implementation of MPI_Alltoallw

[Sudarshan Raghunathan]

Rajeev,

Thank you for your response. I was under the impression that
non-blocking sends and receives are most useful when one is
overlapping communication and computation steps. This does not seem to
be the case in the MPICH implementation of MPI_Alltoallw since there
is no computation per se - all the information is know a priori.

However, I would guess that if one were using custom data types (like
vectors or sub arrays), then the creation of the data types could
perhaps be overlapped with the communication steps (of course, one
could then not call MPI_Alltoallw directly, but just post the isends
and irecvs). I think that gives me something to experiment :-)

Regards,
Sudarshan