[mpi3-coll] Non-blocking Collectives Proposal Draft

Supalov, Alexander alexander.supalov at intel.com
Wed Oct 15 09:09:53 CDT 2008

Hi guys,

I wonder why we stopped using Wiki for the bulky stuff.

Best regards.


-----Original Message-----
From: mpi3-coll-bounces at lists.mpi-forum.org
[mailto:mpi3-coll-bounces at lists.mpi-forum.org] On Behalf Of Christian
Sent: Wednesday, October 15, 2008 4:03 PM
To: MPI-3 Collective Subgroup Discussions
Subject: Re: [mpi3-coll] Non-blocking Collectives Proposal Draft


Thanks a lot for this first draft! I tried to make some useful comments 
and attached the results to this mail (sorry, I can't comment PDFs so I 
did it the "old inconvenient way").

@Working Group (something to discuss):

1) The MPI-2.1 document has 127 occurrences of "nonblocking" and only 8 
occurrences of "non-blocking". What would be the correct term? Should we

try to be more consistent?

2) Clarification of MPI_Request_free() for requests from non-blocking 
collective operations.

3) Better definition/description for "matching" (there is nothing like 
"at the same time" -> logical order?).

4) Define "levels of progression"? To be queried (e.g., for "Synchronous

Progress" MPI_Tests are needed for performance, but for "Asynchronous 
Progress" they would only add unnecessary overhead)? UP >= AP >= SP?

5) "Unexpected Progress" => "buffered" collectives?

6) NBC gives several possible ways for optimizations. With this "General

advice to implementers" we stick to only one, and might prevent others. 
Can we already fix a decision for optimization strategies at this stage?

Should we fix it at all?

7) Should there be a concrete code example in the proposal (e.g. an 
implementation of this double buffering example)?

Hope this isn't too much for now.

Best regards,

Torsten Hoefler wrote:
> Hello Working Group,
> I finished a first draft of our non-blocking collectives proposal.
> Please read it carefully and send comments to me or the list (e.g.,
> marked-up pdf documents).
> The draft is attached to this mail.
> All the Best,
>   Torsten

Christian Siebert, Dipl.-Inf.               Research Associate

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