[mpi3-coll] Nonblocking collectives standard draft
siebert at it.neclab.eu
Mon Nov 24 09:09:57 CST 2008
Hi Torsten et al.,
> the new version is in the wiki  and at . Please check!
Much better, thanks!
I did a second reading and found several but only minor issues with the
text. If you send me the TeX sources, I can send you my proposed
corrections/improvements directly as a patch file (diff).
Some more things for discussion:
- p. 49 l. 41: MPI has the concept of error handlers. I don't see a
reason why we should forbid ("return an error code") its usage. My
suggestion is to simply delete the two sentences (from "If the call ..."
to "... cases.").
- p. 61 l 33-38: Should we really keep this Advice for implementors
(same result for MPI_IREDUCE when called with same arguments)? For the
blocking variant, there stands this argument of reproducibility vs.
performance. However, the non-blocking variant could be optimized much
better (e.g., might handle bad process skew) and we should consider to
weaken this semantic restriction to allow this better performance.
- another argument _for_ MPI_REQUEST_FREE is the existence of
intercommunicators where all processes (i.e., in group A and in group B)
have to call the collective but only part of them might be involved
(e.g., for MPI_IBCAST all but the root process in group A don't really
participate in the operation - they pass MPI_PROC_NULL as root
argument). So having a lightweight MPI_Wait alternative might not be too
The NBC examples are quite buggy (missing MPI_STATUS in MPI_Recv,
missing semicolons, duplicate usage of same req-argument -> bad Waitall,
...) - but as with the text, I can send you corrected versions in the diff.
Christian Siebert, Dipl.-Inf. Research Associate
NEC Laboratories Europe, NEC Europe Ltd.
Rathausallee 10, D-53757 Sankt Augustin, Germany
Phone: +49 (0) 2241 - 92 52 44 Fax: +49 (0) 2241 - 92 52 99
(Registered Office: 1 Victoria Road, London W3 6BL, 2832014)
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