6.0.x Feature List

Time Line

Target date - Q1CY25.

List of Features planned for the 6.0.x release stream

MPI 4.0:

• Big count support
  • API level functions (In Progress PR OPEN feedback being addressed)
  • Collective embiggening (discussed at F2F, stage in none v,w functions first) (DONE)
  • Changes to datatype engine/combiner support (could be a challenge)
  • ops framework embiggening (In Progress) PR OPEN)
  • ROMIO refresh
  • Embiggen man pages (Howard, probably will do the way MPICH does this if possible)
  • Embiggen other documentation (which documentation?)
  • Remove hcol component? (its API doesn't support big count and its been superseded by UCC)
• MPI_T events (probably won't do for 6.0.x).

MPI 4.1:

• Memory Kind support:
  • Add memory-kind option
  • Return supported memory kinds
• Other MPI 4.1 items - too embarrassing to think about - see https://github.com/orgs/open-mpi/projects/2

MPI 4.2 ABI:

• If Jake's ABI work is ready, it might help solidify the standard to have our implementation done.
  • Merge ABI work into main, enable it only when requested, and stress in documentation it is experimental.

PRRTE switch Phase 1

• Documentation Changes (partially DONE UofL)
• Prefix prte binary names (DONE UofL)
• Remove --with-prrte configure option from ompi (DONE UofL)
• Remove unneeded MCA components and frameworks (DONE UofL/rhc54)
• Need to merge UofL changes into whatever solution we find for a PRRTE embedded in OMPI solution for 6.0.x. Note some UofL changes are in the OMPI source code.

Accelerator support:

• extended accelerator API functionality (IPC) and conversion of the last components to use accelerator API (DONE for ROCM and CUDA, not ZE).
• level zero (ze) accelerator component (DONE basic support, IPC not implemented, Howard)
• support for MPI 4.1 memory kinds info object (assume we have PRRTE move, 1 month for basic support)
• reduction op (and others) offload support (Joseph estimates 1-2 months to get in)
• SMSC accelerator (Edgar - not sure yet about this one for 6.0.x)
  • Stream-aware datatype engine.
• Datatype engine accelerator awareness(e.g. memcpy2d) (George).

Things to remove:

• GNI BTL - no longer have access to systems to support this (Howard) (DONE)
• UDREG Rcache - no longer have access to systems that can use this (Howard) (DONE)
• FS/PVFS2 an FBTL/PVFS2 - no longer have access to systems to support this (Edgar) (DONE)
• coll/sm (DONE)
• Remove TKR version of use mpi module. (Howard)
  • This was deferred from 4.0.x because in April/May 2018 (and then deferred again from v5.0.x in October 2018), it was discovered that:
    1. The RHEL 7.x default gcc (4.8.5) still uses the TKR mpi module
    2. The NAG compiler still uses the TKR mpi module.

Collectives:

• mca/coll: blocking reduction on accelerator (this is discussed above, Joseph)
• mca/coll: hierarchical MPI_Alltoall(v), MPI_Gatherv, MPI_Scatterv. (various orgs working on this)
• mca/coll: new algorithms (various orgs working on this)

There are quite a few open PRs related to collectives. Can some of these get merged? See notes from 2024 F2F Meeting

Random:

• Sessions - add support for UCX PML (Howard, 2-3 weeks) (DONE)
• Sessions - various small fixes (Howard, 1 month) (DONE)
• ZE support for IPC (maybe)
• Atomics - can we just rely on C11 and remove some of this code? We are currently using gcc atomics for performance reasons. Joseph would like to have a wrapper for atomic types and direct load/store access.

Likely to miss the 6.0.0 release

• Phase 2 PRRTE
  • MCA parameters move into ompi namespace.
  • prte_info is gone, move those to ompi_info, perhaps a prte-mca option?
• BTL Self accelerator aware (probably defer to later release)
• What about smart pointers?