[mpi3-coll] Comments on nonblocking collectives section

Bronis R. de Supinski bronis at llnl.gov
Tue Jan 27 10:19:25 CST 2009

Torsten and Jesper:

> > sorry for my late input. I've had time to read the document, and have found
> > something. I refer to the version of 21st January.
> Thanks for your review - I'll comment below!

I'm clipping items on which I have no comments.

> > p. 49, line 26:
> > "the performance of many systems..." ->
> > "the performance of many applications can be improved by overlapping communication
> > and computation, and many systems enable this."
> fixed
> > p. 49, line 28:
> > "utilize overlap -> "exploit overlap"
> fixed

Reasonable. I see a split infinitive there also:

to utilize overlap and avoid synchronization =>

to exploit overlap and to avoid synchronization

> > p. 49, line 32:
> > drop "the use of" (grammar: "the use of" is no mechanism)
> nb collective communication doesn't increase performance by itself, only
> the correct *use* of them leads to higher performance, cf. MPI-2.1
> p47:45. I changed "the use of" to "to use" which might be better
> English.

That does sound better. You could delete "mechanism" in "An alternative
mechanism" earlier in the sentence since "to use collective communication"
no longer seems like a mechanism but an implementation choice but it is
not critical.

> > p.49, line 35:
> > "a collective communication, which..." -> "a collective communication
> > operation, that..." ("that" better than "which" here?)
> don't know - I'll leave it as is since Bronis didn't comment on this
> before

Proper English uses "that" with no comma for required clauses -- clauses
without which the sentence does not make sense -- and "which" preceded
by a comma for all others (usually apository but can have other
functions). This clause does not seem required to me so I would go
with ", which" but I could see an argument for "that". In any event,
", that" would be incorrect.

> > p.50, line 35:
> > "In particular," -> "This means that"
> fixed

Hmm. I think at this point neither of these phrases really are needed.
I would just use a colon instead of breaking the two sentences:

Blocking and nonblocking collective operations are different collective
operations: if some process calls a collective operation, all other
processes in the communicator must eventually call the same collective
operation, and no other collective operation in between.

You might insert "blocking or nonblocking" between "same" and "collective"
but I don't think it is critical.

> > p.50, line 48:
> > "collective operations is required" -> "collective operation semantics
> > is required"
> I don't understand this proposal and I think the current text is
> precise.

I agree with Torsten.


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