Jeff Squyres wrote:
> This sounds
> right. It's been eons since I've looked at the GM code in LAM, but the
> short sends are eager and the long sends use a rendezvous protocol.
> Specifically, the main content of the message won't be sent for a "long"
> message until the receiver ACKs that a matching MPI receive has been
> posted.
>
> This is, among other reasons, to help prevent resource exhaustion at the
> receiver.
>
> I believe that there is an SSI parameter to change the size of short /
> long messages, but I don't recall what it is offhand. Did you look in
> the LAM/MPI User's Guide? I seem to recall documenting all such things
> in there...
>
>
> --Jeff Squyres
> Cisco Systems
>
>
Yes, I know about param rpi_gm_tinymsglen. But the point is, Recv
depends on completion of Wait in proc-sender, whereas data transmission
had been finished a long time ago - there is large enough space between
Isend and Wait. In my opinion, the natural behavior of such
communication pattern is completion of Recv as soon as data has arrived.
But in practice, in case of large buffer, receiver can be paused for
arbitrary period.
WBR, Vartan Padaryan.
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