DomainDecomposition.coarsen, refine fix, ghost-sync fixes in axpy and essential BCs - #91
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coarsen(factors) builds an aligned coarse decomposition sharing the process topology of self (needed for geometric multigrid). refine() now shares the topology too instead of re-running compute_dims/Create_cart on the old ncells without mpi_dims_mask, and computes local_ncells from the new starts/ends. Bump version to 0.3.0. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Zeroing boundary coefficients left ghost copies on neighbouring processes stale while ghost_regions_in_sync stayed True, so a following StencilMatrix or derivative dot used outdated values. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
y += a*x left y marked in sync when x was not (stale ghost data in y) and wrongly changed the flag of the input x. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Paired struphy PR: struphy-hub/struphy#91 (the struphy CI runs against this branch via the submodule pointer). |
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Needed for geometric multigrid in struphy (paired struphy PR: struphy-hub/struphy#91), plus two ghost-region bug fixes found while testing it under MPI.
Changes
DomainDecomposition.coarsen(factors)(new). Builds the decomposition of a coarsened grid that is aligned withself: every process owns exactly the coarse cells covering its fine cells. It shares the process topology and communicators, so it is not collective. RaisesValueErrorif starts/ends are not divisible by the factor.DomainDecomposition.refinefixed.compute_dims/Create_carton the oldncellswithoutmpi_dims_mask, so it could pick a different process grid. It also calledCreate_cartagain, which every rank has to join.local_ncellsfrom the old starts/ends.Both methods now use one helper,
_with_element_partition, which validates the partition.apply_essential_bc_stencilnow setsghost_regions_in_sync = Falseon vectors. Boundary coefficients may be ghost entries of neighbouring processes. Those kept stale values while still being marked in sync, so the next matrix-vector product used outdated data.StencilVectorSpace.axpy(behindmul_iadd) updated the sync flag of the inputxinstead of the outputy.y += a*xtherefore stayed marked in sync whenxwas not.Version bumped to 0.3.0.
Tests
ddm/tests/test_coarsen.py(serial +mpi),api/tests/test_essential_bc_ghosts.py(serial +mpi),linalg/tests/test_axpy_ghost_sync.py.linalgserial tests: 7544 passed.femMPI tests on 4 ranks: 144 passed.test_cart_3d.py,test_block.pyandtest_toarray.pyfail to collect locally because theparallelmarker is not registered. That was already the case ondevel-tiny.🤖 Generated with Claude Code