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Document verified Schur coverage and MPI fixture limitation

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Emily Boudreaux
2026-09-17 17:06:26 -04:00
parent fcb7833844
commit c2bd8fc9c9
1 changed files with 58 additions and 8 deletions
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experiments/GRAVITY_CONSISTENT_SCHUR_2026-09-18.md
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@@ -108,12 +108,62 @@ The added FEM integration test compares sparse and matrix-free reduced divergenc
and transpose actions on three dense vectors, compares the full refined action
against the matrix-free coupling implementation, and checks zero-sweep exact
equivalence using identical child inverses. It repeats these checks after geometry
and discretization revisions and tests stale rejection, cache rebuilding, and
collective option mismatch rejection when run on multiple ranks.
and discretization revisions and tests stale rejection and cache rebuilding.
It also contains collective option-mismatch checks for multiple ranks, but those
checks have not executed successfully in the actual FEM fixture; see the MPI
limit below.
Tests are provided for the coordinated build/test campaign; no benchmark result
or production improvement is claimed by this implementation note. Compare the
new policy against the default using the same mass backend, AMG cycles, material
inverse, full-J operator, saved right-hand sides, and scalar-border sources.
Evaluate independent and two-way stellar-structure policies separately so a
coupling change is not mistaken for a gravity-inverse improvement.
No benchmark result or production improvement is claimed by this implementation
note. Compare the new policy against the default using the same mass backend,
AMG cycles, material inverse, full-J operator, saved right-hand sides, and
scalar-border sources. Evaluate independent and two-way stellar-structure
policies separately so a coupling change is not mistaken for a gravity-inverse
improvement.
### Executed coverage and MPI limit
The retained `tests_v1` executable built from commit
`dc8d4b0501e2775b0d1938005e142411319d78b1` passed the focused serial selection:
**20 cases and 441,978 assertions**, including the new real-FEM Schur refinement
and cached stellar cross-action checks. Its SHA-256 is
`e11a49ebadc85206fad5a998b5cc6ee3ac074b498d09b3578d9ef5e0c5d0c04b`.
The same executable passed **13 cases and 213 assertions per rank** on two ranks
with selection
`[gravity_block][unit],[preconditioning][stellar_structure][unit],[coupled_shape_coarse]`.
This verifies the selected algebra and distributed coarse tests. It does not
establish distributed FEM Schur assembly, refresh, or option-mismatch handling.
The broader two-rank selection aborted before reaching the new Schur FEM test.
The existing `Prepared Gravity Block Diagonal Is Legacy Equivalent And Allocation
Stable` fixture constructs `PreparedMappedHDivMassOperator`, whose constructor
requires both a stellar element and a compactified vacuum element **on each
rank**. Rank 1 has no vacuum element in the production partition of
`sandbox.smesh`, so construction calls `MPI_ABORT` at that pre-existing check.
`fem::setup_fem` currently calls `GeneratePartitioning(rankCount, 1)` internally;
there is no partition override in the existing setup interface. A lightweight,
read-only reconstruction of the mesh dual graph and installed METIS 4 partition
call, using MFEM's descending adjacency order, reproduced the following split:
| Mesh | Rank | Core | Envelope | Vacuum |
| --- | ---: | ---: | ---: | ---: |
| `sandbox.smesh` | 0 | 0 | 220 | 384 |
| `sandbox.smesh` | 1 | 448 | 164 | 0 |
| Existing one-level refined mesh | 0 | 0 | 1,673 | 3,072 |
| Existing one-level refined mesh | 1 | 3,584 | 1,399 | 0 |
The refined mesh therefore has the same obstruction; it was inspected through
its partition graph, not subjected to another FEM run. Selecting only the new
test cannot remove its shared geometry-construction prerequisite. A deliberate
partition distributing every material across both ranks could exercise that
fixture, but adding a partition-injection seam is outside this preconditioner
experiment. Production mesh setup and partitioning remain unchanged.
The precise current validation claim is **serial FEM plus two-rank algebra/coarse
coverage**. Actual FEM Schur refinement, its distributed sparse-cache lifecycle,
and its collective option-rejection branches remain unvalidated on multiple
ranks. Logs, executable hashes, and commands are retained in the workspace under
`diagnostics/preconditioner_improvement_2026-09-18/tests_v1/`, specifically
`provenance.json`, `serial.log`, `mpi2.log`, `mpi2_units.json`, and
`mpi2_units.log`.