- Add mpi_stub.h providing all MPI types/constants/functions as no-ops
(nprocs=1, myrank=0) with memcpy-based Allreduce and clock_gettime Wtime
- Replace #include <mpi.h> with conditional #ifdef MPI_STUB in 31 files
(19 headers + 12 source files) preserving ability to build with real MPI
- Change makefile.inc: CLINKER mpiicpx->icpx, add -DMPI_STUB to CXXAPPFLAGS
- Update makefile_and_run.py: run ./ABE directly instead of mpirun -np N
- Set MPI_processes=1 in AMSS_NCKU_Input.py
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Cache Sync in RestrictProlong: replace 11 basic Parallel::Sync() calls
with Parallel::Sync_cached() across RestrictProlong, RestrictProlong_aux,
and ProlongRestrict to avoid rebuilding grid segment lists every call.
Merge paired MPI_Allreduce in surface_integral: combine 9 pairs of
consecutive RP/IP Allreduce calls into single calls with count=2*NN.
Merge scalar MPI_Allreduce in surf_MassPAng: combine 3 groups of 7
scalar Allreduce calls (mass + angular/linear momentum) into single
calls with count=7.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Phase 1: Merge N+1 transfer() calls into a single transfer() per
Sync(PatchList), reducing N+1 MPI_Waitall barriers to 1 via new
Sync_merged() that collects all intra-patch and inter-patch grid
segment lists into combined per-rank arrays.
Phase 2: Cache grid segment lists and reuse grow-only communication
buffers across RK4 substeps via SyncCache struct. Caches are per-level
and per-variable-list (predictor/corrector), invalidated on regrid.
Eliminates redundant build_ghost_gsl/build_owned_gsl0/build_gstl
rebuilds and malloc/free cycles between regrids.
Phase 3: Split Sync into async Sync_start/Sync_finish to overlap
Cartesian ghost zone exchange (MPI_Isend/Irecv) with Shell patch
synchronization. Uses MPI tag 2 to avoid conflicts with SH->Synch()
which uses transfer() with tag 1.
Also updates makefile.inc paths and flags for local build environment.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
