Charm++ 9.0.0-alpha2

Second pre-release of the 9.0 line, cut from 'recharm' at 247c38f
(reconverse b23a7fb). It is the last tag that still carries the classic
Converse sources and machine layers; they are deleted right after it
(#4056), so this tag marks the end of the two-runtime tree. Everything
below is new since v9.0.0-alpha1 (2026-10-16).

Runtime (reconverse):

• User-driven interop: CharmBeginInit / CharmInit / CharmLibExit work on
  reconverse, so a program can run Charm++ phases from its own main
  (#4055, reconverse #288). CharmLibInit with an MPI communicator still
  aborts; MPI interop stays on the list.

• Idle PEs reach the idle condition after one empty network poll instead
  of a sweep of about forty: quiescence detection across two processes
  settles in 0.4 ms instead of 10 ms on the libfabric TCP provider, and
  cross-process ping-pong latency on that provider halves (reconverse
  #290).

• Slingshot (libfabric cxi): the LCI registration cache is off and RX
  matching is hybrid, so FI_MR_CACHE_MONITOR and FI_CXI_RX_MATCH_MODE no
  longer need to be set in the environment (reconverse #281).

• ++quiet suppresses CmiPrintf output and the startup banners; abort
  reasons always go to stderr (reconverse #289).

Charm++:

• 64-bit object ids, parts 1 and 2 (#4015, #4057, #4058, #4060): ids
  minted from per-process tranches with a PE-0 allocator, restart with
  any process count, a deleted index re-created under a new id is
  re-addressed at its home, and an opt-in wide-collection layout (24
  collection bits, 37-bit packed index; CkArrayOptions::setWideCollection)
  for programs that create many small arrays. Maintainer documentation
  in doc/internals/object-ids.md.

• AMPI stage 0: TCharm and AMPI build and run on reconverse without
  thread migration (#4051). tests/ampi runs in CI, single and
  two-process. Migration, checkpoint, isomalloc, -pieglobals and
  -tlsglobals are not available on reconverse yet.

• Tests: the classic-only queue, queueperf, megacon and commlib tests are
  gone and ten stale tests and examples build again (#4048); the CI tier
  gained amr_1d_simple, dynamic_insertion, dynamic_insertion_deletion,
  objid_insert, objid_wide and the user-driven-interop example.

Known gaps and issues in this alpha:

• With several processes per host, +setcpuaffinity without +pemap binds
  every process to the same cores (reconverse #276; fix in progress).
  Use an explicit +pemap for multi-process-per-host runs.

• When one rank calls CmiAbort under srun, the other ranks keep running
  until the job's time limit (reconverse #285; fix in progress). Launch
  with 'srun -K' or wrap srun in 'timeout'. lcrun from LCI master already
  ends the job; reconverse's pinned LCI predates that.

• AMPI thread migration, CharmDebug, Windows multicore: not available.

• Checkpoint files written by an alpha may not be readable by later 9.0
  pre-releases; the object id layout is final at the beta.

• CkMulticast delegation can hang under +randomized_msgq (#4032).

Getting the source:

git clone --branch v9.0.0-alpha2 --recurse-submodules https://github.com/charmplusplus/charm
cd charm && ./build charm++ reconverse-linux-x86_64 --with-production -j8

Tested at this tag (2026-10-19):

• macOS arm64 (reconverse-darwin-arm8, production): the full sweep of 186
  test, example and benchmark directories, single process and two
  processes, on the classic-deletion branch merged at this tip (the
  deletion does not change the tested code); the same 13 pre-existing
  failures as before (#4035). AMPI built and tests/ampi run single and
  two-process. objid_wide, pingpong, megatest, user-driven interop.
• Purdue Anvil, 1 node, 2 processes, InfiniBand (libfabric verbs): the
  CI test set in one and two processes, pingpong, megatest with 2 x 16
  PEs, on this exact tip (job 21539122, 38 of 38) and on the tip minus
  #4060 (job 21536948).
• NCSA Delta, 2 nodes, Slingshot-11: the same set on the same tree,
  without the FI_MR_CACHE_MONITOR / FI_CXI_RX_MATCH_MODE settings that
  earlier runs needed (reconverse #281).