[mpiwg-sessions] meet today

HOLMES Daniel d.holmes at epcc.ed.ac.uk
Mon Apr 22 11:47:01 CDT 2019

Hi Howard,

I’ll be there today.

We need to figure out what our purpose is for the meeting on 24th April - or cancel our involvement. Martin added two for us so they existed but we don’t have to use the 2nd one if we have nothing new to present/ask/etc.

Point of information: the "function pointers” group just decided today that explicit function pointers as part of the MPI user-facing interface, are not necessary for any of the use-cases for which they were proposed. Thus, we are likely not going to get function pointers + sessions any time ever. This is not a bad thing because one of those driving use-cases for function pointers was sessions - we convinced ourselves that the function pointers needed for sessions, e.g. to support different thread support levels, can be hidden behind the existing MPI functions and opaque handles. For example, the MPI_Request handle could lead to a function pointer for the actual “wait” function inside the MPI library and another for the actual “test” function. The MPI_WAIT and MPI_TEST functions will then be implemented as straightforward delegation shim functions that call down into the appropriate function pointer from the passed-in MPI_Request parameter. We should socialise that proposed approach with Aurelien (in particular) because he voted against sessions in the Chattanooga straw poll because of the perceived lack of support for multiple thread support levels in use at the same time.

Dr Daniel Holmes PhD
Applications Consultant in HPC Research
d.holmes at epcc.ed.ac.uk<mailto:d.holmes at epcc.ed.ac.uk>
Phone: +44 (0) 131 651 3465
Mobile: +44 (0) 7940 524 088
Address: Room 2.09, Bayes Centre, 47 Potterrow, Central Area, Edinburgh, EH8 9BT
The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

On 22 Apr 2019, at 17:16, Pritchard Jr., Howard via mpiwg-sessions <mpiwg-sessions at lists.mpi-forum.org<mailto:mpiwg-sessions at lists.mpi-forum.org>> wrote:

HI Sessions activists,

If possible, I’d like to meet today to discuss


as well as what to knock off next in


Reminder we have an hour in the upcoming virtual forum on 4/24.




Howard Pritchard
Los Alamos National Laboratory

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