[mpi3-coll] Non-blocking Collectives Proposal Draft

Torsten Hoefler htor at cs.indiana.edu
Thu Oct 16 15:46:16 CDT 2008

Hello Alexander,
> Generally, some sentences start with lower case letters that should be
> capitalized.
yes, I fixed some but will re-read it later this week.

> Page 3, top. We probably should not explain here how to ensure progress
> for nonblocking ops. This matter should be covered by the general
> progress description elsewhere.
I agree, I deleted it (it's already in the nonblocking point-to-point

> Page 3, lower half. Look how progress is defined in this list by
> referring to the pt2pt progress rules.
what do you mean with that? I would just reference the current MPI
definition - NBCs seem to fit this model nicely.

> Ibid. There are already 3 classes of requests: pt2pt, generalized, and
> file I/O ones.

> Page 3, bottom. How many nonblocking ops can overlap with a blocking
> one? I.e., can one have the following situation:
> Process 0			Process 1
> MPI_Ibarrier(req)		MPI_Ibarrier(req)
> MPI_Wait(req)
> MPI Bcast			MPI_Bcast
> 				MPI_Wait(req)
yes, this is a legal code and should work. Any objections?

> Page 5, bottom. 32767 simultaneous ops to support is a tall order. I'd
> say, 1 (one) would be a good lower limit, thus allowing no overlap. Or
> even 0 (zero), meaning no nonblocking collective support at all. The
> rest of this passage would probably be better reformulated as an advice
> to implementors.
yes it is - I'm very indicisive. We have to discuss this at the Forum in

> In the margin: editing a PDF requires creativity (exemplified by the
> earlier comments) or a pretty expensive Acrobat. Maybe we can find some
> other way of distributing and commenting on our drafts?
oh yes, I fully agree. But the final document should be in MPI style, so
I thought I should start with LaTeX. Do you have any suggestions? Wiki
seems suboptimal because we would have to re-format everything (which
might be not too bad). LaTeX source in svn would be the best, but does
everybody have LaTeX? I'm open for any suggestion!

For now, I uploaded the changed version to the wikipage (to avoid
attachments on the mailinglist):

Thanks for the comments!


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Torsten Hoefler       | Postdoctoral Researcher
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