I prefer option 2. On Wed, 25 Feb 2009, 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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