Meeting Notes

June 11 - June 14, 2018

MPI Forum Working Groups

Various working groups met. Notes can be found on their respective wikis:

  • Sessions
  • Tools
  • Persistence
  • Hardware Topology
  • Fault Tolerance
  • Collectives (and groups and communicators)
  • Hybrid

MPI Forum Plenaries

Upcoming Meeting Dates and Locations

  • March 4 - 9: Chattanooga, TN
  • May 28 - 31: Chicago, IL
  • Shifted to Tuesday - Friday to avoid Memorial Day holiday in the US
  • September 5 - 9: Zürich, Switzerland
  • Thursday - Saturday before EuroMPI to avoid Labor Day holiday before and conflicts after the conference
  • December 9 - 12: Albuquerque, NM

Introduction

Martin began the plenary portion of the F2F with introductions and working group updates.

  • No objection

Reading: Errata: Possible ambiguity on size of array_of_indices and array_of_statuses?

  • No objection

Reading: Errata: MPI_STATUS_SET_CANCELED F08 binding: flag param intent

  • No objection

Reading: Errata: Behavior of MPI_Dims_create when ndims is zero

  • Open MPI and MPICH are already doing this.
  • No objection

Reading: Errata: Clarification to allow MPI_PROC_NULL as neighbor in (distributed) graph topologies

  • Rich raised performance concerns that implementations which do not use the existing point-to-point code to implement this (which MPICH and Open MPI already do) will be impacted because they will need to shuffle around buffers and do additional checks for MPI_PROC_NULL.
  • Agreed that this is not an errata change and should go through the full voting procedure.
  • This will give everyone a chance to discuss this before the first vote in September.

Reading: No-No: Noncatastrophic Errors

  • No objections

Reading: No-No: MPI_T: Consistent reference to MPI processes

  • No objections

Reading: Deprecate MPI_SIZEOF in MPI-4.0

  • Asked for minor whitespace change and additional text to point out that some compilers may not support storage_size.
  • Pushback from Jeffs Squyres and Hammond that no available, current compiler falls into this category and we should not make those changes.

Discussion on Draft Standard and MPI-next

  • Tentative targets
    • Draft standard at SC19
    • Release candidate meeting Dec 2019
    • Ratification meeting March 2020

Plenary on status, open issues (13, 17, 18, 19, 30, 64)

No-no: Errata: Possible ambiguity on size of array_of_indices and array_of_statuses?

  • Dan made a few small modifications to the reading from the previous day to make the text more consistent with the rest of the standard.
  • More changes were needed and it was agreed to fix this for a future meeting.

Reading: New functions to create communicators from groups

  • Dan gave an overview of tickets #93, 94, and #95
  • The question was raised about deprecating MPI_COMM_CREATE_GROUP and Dan responed that it is more likely that MPI_COMM_CREATE_GROUP would be changed to allow MPI_COMM_NULL and change the name of these new functions to drop FROM.
  • Rich raised concerns that relying on group manipulation would have serious performance implications on hardware.
  • Many folks weren’t sure that this proposal made sense outside the context of Sessions because it didn’t provide a big difference over MPI_COMM_CREATE_GROUP.
  • Further notes here

Reading: New functions to create files from groups

  • Decided not to read this proposal in light of the discussion for #93

Reading: Info key(s) for Persistent Collective Communication

  • Tony read this proposal. There were a number of changes suggested.
  • The proposal was well received but determined that it needed to be reread in September.

Reading: Non-blocking communicator/file/win constructors/destructors/etc

  • Tony read this proposal.
  • The decision was made to re-read the proposal based on the feedback from the room.

Reading: Nonblocking functionality for the Process Creation and Management Chapter

  • Tony read this proposal.
  • The decision was made to re-read the proposal based on the feedback from the room.

Reading: Nonblocking constructor/destructor(s) for the One-sided Communication RMA Chapter

  • Tony read this proposal.
  • The decision was made to re-read the proposal based on the feedback from the room.

Discussion: Front matter text clarifications for the “Collective Communication” and “Topology” Chapters

  • Puri read the document. Originally this was scheduled to be an official reading, but changes were made during the working group session and the was converted to an unofficial reading.
  • A straw poll was taken on whether to re-organize Chapter 2 to put similar operations together. It passed almost unanimously.

Discussion: WITH_INFO review across the collective API

Discussion: WITH_INFO review correlated to Tickets 80 and 84 for collective operations

Discussion: Collectives WG Update

Discussion: Splitting ULFM

Discussion: HW Topology WG Update

Discussion: Sessions Update

Discussion: MPI BigCount - what is next?