Can someone tell me the best replacement for the following pattern if freeing active requests is made erroneous? void send_fire_and_forget_ack(int target, MPI_Comm comm) { MPI_Request request; MPI_Isend(NULL, 0, MPI_BYTE, target, special_tag, comm, &request); MPI_Request_free(&request); return; } The reason to not use MPI_Send here is it can block on resource exhaustion. Note that this is a real usage model. One of my applications send fire-and-forget acks and it was a performance issue on Blue Gene/Q. Because we send a payload - it is unclear if this is actually necessary - I replaced MPI_Send with MPI_Bsend to solve the problem (yes, Bsend really does help here), but we could instead use Isend+Request_free (which would be easy since our payload is trivial and could be a global const). The reason I bring this up even though Bsend works for us is that I would much rather deprecate Bsend that make freeing active requests erroneous. Jeff On Mon, Dec 14, 2015 at 7:55 AM, Daniel Holmes <[email protected]> wrote:

Hi all,

The next point-to-point teleconference will be Monday 18th January 2016 at 11am Central US via webex.

I will send out another reminder nearer the time.

Tentative agenda:

MPI-4.0, issue #11: add communicator assertions (remember implications for tools!) MPI-4.0, issue #26: deprecate cancel for send requests

MPI-4.0, issue TBD: add ARECV/FSEND MPI-4.0, issue TBD: deal with minor correction to MPI_WAIT raised by Bill and Rajeev (a la Bill's email 29/06/2015) * MPI-4.0, issue TBD: deprecate request free for active receive requests (arising from Dec 2015 meeting)* MPI-4.0, issue TBD: define batch requests (a la Pavan's email of 14/12/2015)

* MPI-Next, issue TBD: disallow request free for active receive requests (i.e. upgrade advice to erroneous)* MPI-Next, issue #27: disallow cancel for send requests (i.e. upgrade advice to erroneous)

Cheers, Dan.

-- Dan Holmes Applications Consultant in HPC Research EPCC, The University of Edinburgh James Clerk Maxwell Building The Kings Buildings Peter Guthrie Tait Road Edinburgh EH9 3FD T: +44(0)131 651 3465 E: [email protected]

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-- Jeff Hammond [email protected] http://jeffhammond.github.io/