[mpi3-coll] NBC Draft Revision 5

[Jesper Larsson Traeff]

I'm also for option 2

Jesper

On Wed, Feb 25, 2009 at 11:29:17AM -0800, Adam Moody wrote:
> Hello all,
> I opened a ticket to add the text to the collective intro regarding 
> access restrictions on MPI_IN_PLACE like we have in the NBC proposal:
>    https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/131
> Erez reviewed it and pointed out that it's not really necessary.  All 
> collectives specify MPI_IN_PLACE should be applied to the receive buffer 
> which has the stronger constraint, except for the root in scatter and 
> scatterv which does not receive anything.  Then, after I looked over 
> things again, I realized that my current statements are actually more 
> restrictive than they need to be for scatter{v}.
> 
>    "When using the "in place" option, message buffers function as both 
> send and receive buffers. Such buffers should not be modified or 
> accessed until the operation completes."
> 
> Since nothing is received at the root in scatter{v}, it could in fact 
> issue several NBC scatter{v} calls on different communicators (reusing 
> an active send buffer).  To fix this, we have two options;
>    1)  Change "When using the 'in place' option, message buffers 
> function"  to  "When using the 'in place' option, receive message 
> buffers may function"
>    2)  Close ticket 131 and strike the similar lines in the NBC 
> proposal -- just rely on the implicit send/receive buffer constraints
> I'm in favor of option #2 myself, since I'm not sure how much info #1 adds.
> 
> If we go with option #2, it would leave a single-sentence paragraph on 
> page 51, line 11 in the NBCv5 text.  We could append this sentence to 
> the paragraph above it.
> 
> Any opinions?
> -Adam
> 
> Torsten Hoefler wrote:
> 
> >Hello workgroup,
> >I just posted revision 5 of the NBC draft to ticket #109.
> >
> >The draft is also available at [1] and a diff to revision 4 at [2].
> >
> >[1]: http:// www. unixer.de/sec/nbc-proposal-rev-5.pdf
> >[2]: http:// www. unixer.de/sec/nbc-proposal-rev-5.diff
> >
> >Please review and comment!
> >
> >All the Best,
> > Torsten
> >
> > 
> >
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