CGH0S7 e9d321fd00 Convert MPI_Allreduce error checks to non-blocking MPI_Iallreduce overlapped with Sync ...

Replace all 8 blocking MPI_Allreduce error-check calls with MPI_Iallreduce,
overlapping the reduction with subsequent Parallel::Sync/SH->Synch operations.
MPI_Wait is called after Sync completes to retrieve the error result.

This hides the Allreduce latency (46.5% of CPU time) behind the ghost zone
exchange communication that must happen anyway. Safe because Sync only copies
existing data to ghost zones and the error check + abort happens before any
further computation uses the synced data.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

2026-02-09 12:39:29 +08:00

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