> But the MPI standard says this is valid and can be used to avoid the
need
> to keep track of ISEND request handles. It is clear that if the
matching
> RECV has completed then the unaltered content of the ISEND buffer is
no
> longer needed. The RECV cannot have completed unless the message got
out.
I tend to agree with this sentiment, but the MPI standard has long had a
prohibition on touching the transmit buffer, because you never know what
the implementation is using that buffer for. So... anything that ever
had a reliability protocol and did zero copy has had this issue.
> Erez is pointing out a case where the semantic stipulated by the MPI
> standard back before RDMA adapters were available becomes flawed with
the
> way RDMA adapters now work. The content of the ISEND buffer is
irrelevant
> once the destination RECV has completed but some other things about
the
> ISEND buffer are still in limbo
I don't believe this is new. Anything that ever provided a reason that
you couldn't touch the send buffer likely had a similar issue.
Keith
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