The second owner of one blocked level goes. Its capability is the
zero-refinement FixedPatchStepper added in f764d68/985db14 (periodic SRT
level, stationary passive circles, shifted storage, NaN spare, single wait),
which matched it array for array on GPU at 1318fc2 (3 splits x +-circle x
shifted/unshifted) and passes the host lifecycle and fault contracts.
API change for callers:
PeriodicBlockStepper(cfg, BlockLayout2D.build(ny, nx, by, bx), context=c, objects=o)
-> FixedPatchStepper(cfg, context=c, refinements=[], level_blocks=[(by, bx)],
level_objects=[tuple(o)])
download() returns a 1-tuple; static-circle tables are
_level_boundaries[0].tables (was .boundary); no free-memory preflight.
- lbm/block_stepper.py deleted; MAX_GRID_DIM lives in refinement_stepper.
- tests/validation/multigrid/test_block_stepper.py: same frozen GPU gates
(split identity, FP64 oracle, circle across seams) and pre-CUDA rejection
cases on the single level; the old-vs-new bitwise test is retired with the
old class (its result is the 1318fc2 record).
- tests/unit/test_block_step_sync.py folded into test_single_level.py
(step(n) vs n x step(1) roles and one wait, step(0), mid-batch launch
failure), which also gains bad-state rejection before upload, download
failure and activation-failure retry on close.
- test_shifted_storage and test_raw_exchange_gpu use the single level; the
raw-exchange reference feeds the AMR Jet column and raw ledger through the
root level boundary instead of patching a private kernel field.
- Pinned historical runners (taylor_green/run_case.py, run_jet_circle_cv.py)
are unchanged: they only run on trees that still ship PeriodicBlockStepper.
No alias.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
