Notes 2018 05 03

Participants

• Jean-Babtiste Besnard
• Chris Chambreau
• James Clark
• Marc-Andre Hermanns
• Nathan Hjelm
• Michael Knobloch

Topics

• Datatype description discussion in get_info

  • We are waiting for feedback from MPICH on derived datatype idea
  • Additional idea came up
    • Return just a single MPI Datatype handle with the basic type of MPI_DATATYPE_NULL for multi-element types
    • Add call MPI_T_event_get_datatype(int event_index, MPI_Datatype *datatype) to query type to use with get_envelope/get_contents
    • Callable only after MPI_Init
    • Tool would have to either buffer all events prior/inside MPI_Init and evaluate them after Init returned
    • Tool could still assume a specific structure (would have to in callbacks that actually compute metrics and not just dump the information)
  • Derived datatypes may make it harder for the implementation
    • Open-MPI has two layers: Opal + Ompi
      • Events can come from the Opal layer, where there are different types (Opal types != Ompi types)
  • 2 Arrays for types & displacements are simpler to process and would fit both Opal and Ompi layer

• Virtual Meetings preparation

  • Add text for MPI_T_event_copy and initial text with additional array parameter on info
  • Prepare Information with specific Pros/Cons for each alternative