[mpi3-coll] July/August telecon

Adam Moody moody20 at llnl.gov
Mon Jul 28 14:57:09 CDT 2008

Hi Torsten,
The two key areas I'd like to work with our users on here at LLNL are 
non-blocking and neighbor-exchange (topological) collectives.  I could 
perhaps also look into the benefits of persistent collectives.  Our 
users would like to start using non-blocking collectives asap -- they 
are excited about this.  I suspect we'll be able to show some real value 
for the neighbor-exchange collectives on our clusters, as well.  And 
given IB's need to pin memory, we may also be show performance gains 
with persistent collectives.

For non-blocking collectives, should I start with libNBC?  Where can I 
get the latest copy of it?  I know you have done some work with 
neighbor-exchange collectives, too.  Do you have a similar library for that?

Torsten Hoefler wrote:

>Hello Collectives-WG,                                                                          
>we propose                                                                      
>   July 31, 12:00pm EDT                                                          
>as the time/date for our monthly collectives workgroup teleconference.          
>Please let us know if there are any strong objections.
>We will mainly be talking about the feedback we got from the whole forum
>on our proposals. My notes are at:
>https:// svn.mpi-forum.org/trac/mpi-forum-web/wiki/forum063008
>Im particular we have to decide (those points also serve as agenda
>1) "One call fits all" vs. "Calls for everything:
>  - we should make a decision on which model we want to use in order to
>    be able to flesh out semantic details of the operations
>2) Do we want/need all combinations that are semantically possible?
>  - the Forum accepted the usefulness of non-blocking collectives as proved
>  - the Forum wants to see more research/use cases for sparse collectives 
>  - the Forum wants to see more research/use cases for persistent colls
>  - who wants to invest time into this?
>3) Updates on topological collectives
>4) Updates on MPI Plans (I have a slightly different
>   proposal/implementation than Christian for the same thing)
>5) Variable size collectives (does anyone pick this topic up?)
>6) MPI-2.2 issues (I will add the WG's proposals to the MPI-2.2 wiki so
>   that this can serve as a base for discussion)
>   a) fix non-scalable graph interface (obvious)
>   b) local reduction operation (needed by libraries, e.g., LibNBC)
>   c) local progress function (caused heavy discussions in Forum)
>   d) request completion callbacks (for better progression, e.g., LibNBC)
>   e) partial pack/unpack (needed by libraries, e.g., LibNBC)
>7) other items   
>Please post any additional proposals items to discuss to the list!
>Thanks & Best,                                                                  
> Andrew Lumsdaine and Torsten Hoefler

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