refactor: remove redundant periodic patch stepper alias

docs/compatibility.md

@@ -3,6 +3,13 @@
 Changes that can make a previously accepted setup or call behave differently.
 Each entry names the commit, the affected entry points and the observable result.
 
+## Redundant periodic stepper alias removed
+
+`PeriodicPatchStepper` is no longer exported from `lbm.refinement_stepper`.
+Use `FixedPatchStepper` with the same arguments, including explicit
+`level_blocks`. The old name was an alias for that exact class; periodic
+boundaries remain the default. Existing imports of the old name must be updated.
+
 ## 87c3a31: cut-link ownership is validated for every body
 
 `validate_cut_link_ownership` (`body/preprocess/flag_overlay.py`) now runs for
@@ -33,18 +40,3 @@ or negative amplitude (the aperture test is geometric). Bodies with neither
 `SurfaceActuation` nor aperture links still raise
 `ValueError("Body has no surface actuation")`. The value is unchanged: the latest
 step's wall/aperture exchange, not total nozzle force.
-
-## 7afb5ad: `Simulation` fails closed after a Jet amplitude device-write failure
-
-`Simulation.set_jet_amplitude` previously only documented that a device error
-leaves the per-link velocity column undefined; the instance stayed usable.
-Now any error after input validation (internal stream creation or the upload)
-marks the Simulation failed. Every later device-touching public method,
-including the `stream` property (guard added in the follow-up repair commit on
-`claude/jet-update-consistency`), raises
-`RuntimeError("Simulation failed (...); close() and recreate it")`. The host
-amplitude keeps its previous value. `close()` still works and stays retryable;
-cached host readers and host staging calls are not blocked. Invalid input
-(`ValueError`/`IndexError`) is unchanged: it raises before any change and the
-instance stays usable. `FixedPatchStepper.set_jet_amplitude` already failed the
-instance (status `failed`) and is unchanged.

docs/lifecycle.md

@@ -7,7 +7,7 @@ it is; it adds no framework. Line references are to candidate 0f8fdbc3.
 |---|---|---|---|
 | 1. Module and its globals | Compile-time (visible to the compiler, fixed per module): `config.h` macros incl. `NX`/`NY`, `COLLISION_MODEL`, `BLOCK_ROOT_BC`, `WALL_*`. Runtime per-module globals (not visible to the compiler; written by host code): `__constant__` `d_params`, `d_w`, `d_cx`, `d_cy`, `d_block_channel`, `d_block_wall`; plus bound kernel handles | Globals are written once by the owner right after `load_module`. Uniform grid: `Simulation._recompile` (construction, body-topology sync) loads a new module and re-uploads; `update_runtime_params` rewrites `d_params` (omega, force, n_objects) between runs. Steppers: never rewritten after construction, so they are immutable for the instance's lifetime although they are runtime values. The blocked slot/reservoir root reads its slot from the `d_block_wall` constant (the former dense route used `WALL_*` macros; both were bit-identical in the parity gates). | Every owner loads its own module (`compiler.load_module` = `module_from_file`, no cache). A loaded module is never shared between live owners: globals are per module, so sharing would share mutable `d_params`. |
 | 2. Geometry, layout, tables | flags, curved-link tables, block layouts and halo pairs, transfer (explode/coalesce) tables, block kinds | Immutable for the life of an instance. Uniform grid: rebuilt by body sync. `FixedPatchStepper`: a geometry change is a new instance (`remap_child`), committed only after a successful transfer. | No in-place table edits. |
-| 3. Controls and dependent boundary columns | Jet amplitude -> per-link `surface_velocity`; body actions (uniform grid) | Between steps, without a table or module rebuild (`set_jet_amplitude`). | Input (index, level, amplitude) is validated before any device write; invalid input changes nothing and the instance stays usable. The host copy commits only after the upload returned. Any error after validation leaves the device column undefined and fails the instance: `FixedPatchStepper` status `failed`, `Simulation._failed`; every later device-touching public method (`Simulation`: `stream`, `set_jet_amplitude`, `initialize`, `sync_bodies`, `run`/`step`, `read_surface_exchange`, `read_body(s)`, `get_macroscopic`, `get_ddf`, `update_runtime_params`, `snapshot`, `restore`, save/load checkpoint) raises; cached host readers and host-side staging (e.g. `get_flags`, `add_body`/`remove_body` before a sync) do not touch the device and stay callable. `close()` still releases resources and stays retryable. |
+| 3. Controls and dependent boundary columns | Jet amplitude -> per-link `surface_velocity`; body actions (uniform grid) | Between steps, without a table or module rebuild (`set_jet_amplitude`). | Host copy commits only after the device upload succeeded; a device error fails the instance. |
 | 4. Per-step state | population double buffers and their parity, raw-exchange ledgers, observations | Device-only during `step(n)` / `run(n)`; buffer swaps are host-handle swaps. | Valid on the host only after the single wait at the end of the call. |
 
 Storage routes are separate concerns:

examples/fixed_periodic_patch.py

@@ -16,7 +16,7 @@ from CelerisLab.config import load_lbm_config
 from CelerisLab.cuda.context import CudaContext
 from CelerisLab.lbm.equilibrium import compute_feq_d2q9, compute_macro_from_ddf
 from CelerisLab.lbm.refinement import ACTIVE
-from CelerisLab.lbm.refinement_stepper import PeriodicPatchStepper
+from CelerisLab.lbm.refinement_stepper import FixedPatchStepper
 
 
 def shear_equilibrium(shape, origin, dx, period):
@@ -48,7 +48,7 @@ def main():
                   nx=16, ny=16, viscosity=.1, velocity=1e-3, rho=1.0,
                   lattice_model="D2Q9", collision="SRT", streaming="double_buffer",
                   store_precision="FP32", ddf_shifting=False, les_enabled=False)
-    with CudaContext(0) as context, PeriodicPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)],
+    with CudaContext(0) as context, FixedPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)],
                                                            level_blocks=[(16, 16), (24, 24)]) as run:
         p = run.patch
         coarse = shear_equilibrium(p.coarse_shape, (0, 0), 1.0, cfg.ny)

src/CelerisLab/lbm/refinement_stepper.py

@@ -910,7 +910,3 @@ class FixedPatchStepper:
     _fine_leaf = property(lambda self: self._leaf[1])
     _child_leaf = property(lambda self: self._leaf[2] if len(self._leaf) > 2 else None)
     _middle_kind = property(lambda self: self.hierarchy.kinds[1] if self.hierarchy.depth > 2 else None)
-
-
-# Preserve the original entry point and its periodic default.
-PeriodicPatchStepper = FixedPatchStepper

src/CelerisLab/simulation.py

@@ -47,7 +47,6 @@ class Simulation:
         # Internal stream for async DTOH coordination
         self._stream: Optional[cuda.Stream] = None
         self._closed = False
-        self._failed = None  # reason after an uncertain device write; only close() remains
 
         # Load configs
         self.lbm_cfg = load_lbm_config(lbm_config_path)
@@ -90,7 +89,6 @@ class Simulation:
     @context_bound
     def stream(self) -> cuda.Stream:
         """Internal CUDA stream for async DTOH coordination."""
-        self._require_usable()
         if self._stream is None:
             self._stream = cuda.Stream()
         return self._stream
@@ -174,27 +172,15 @@ class Simulation:
     def set_jet_amplitude(self, index: int, amplitude: float) -> None:
         """Change one jet's signed amplitude; re-uploads per-link velocity only.
 
-        Invalid input raises before any change. Any error after validation
-        (stream creation or upload) leaves the host amplitude unchanged but the
-        device column undefined, so the Simulation is marked failed: every later
-        device-touching public method (incl. ``stream``) raises; close() still
-        works. Close and recreate it.
+        Invalid input changes nothing. A device error leaves the host amplitude
+        unchanged but the device column undefined: treat it like any other CUDA
+        exception here and close/recreate the Simulation before stepping again.
         """
-        self._require_usable()
         jet = self.bodies.jets[index].with_amplitude(amplitude)
         if self._initialized:
-            try:
-                self.field.curved.set_jet_amplitude(index, amplitude, self.stream)
-            except BaseException as exc:
-                self._failed = f"jet amplitude upload failed: {exc!r}"
-                raise
+            self.field.curved.set_jet_amplitude(index, amplitude, self.stream)
         self.bodies.jets[index] = jet  # later geometry syncs keep the new amplitude
 
-    def _require_usable(self):
-        failed = getattr(self, "_failed", None)
-        if failed is not None:
-            raise RuntimeError(f"Simulation failed ({failed}); close() and recreate it")
-
     def remove_body(self, id: int) -> None:
         """Remove a body from the simulation.
 
@@ -352,7 +338,6 @@ class Simulation:
         Unlike read_body this is not accumulated/time-averaged. It resets after
         geometry sync or checkpoint load; advance before interpreting it.
         """
-        self._require_usable()
         obj = self.bodies.get(id)
         curved = self.field.curved
         has_aperture = (curved.aperture is not None
@@ -380,7 +365,6 @@ class Simulation:
             BodyTelemetry with fields ``force``, ``torque``, ``sensor``.
             ``sensor`` is a dim-length array of zeros for non-sensor bodies.
         """
-        self._require_usable()
         if self.bodies.obs_pinned is None:
             raise RuntimeError("No obs buffer. Call run() first.")
         if stream is None:
@@ -400,7 +384,6 @@ class Simulation:
         This is the most efficient readback for DRL control loops
         (single contiguous D2H copy, no Python per-body overhead).
         """
-        self._require_usable()
         if self.bodies.obs_pinned is None:
             raise RuntimeError("No obs buffer. Call run() first.")
         if stream is None:
@@ -463,7 +446,6 @@ class Simulation:
     @context_bound
     def initialize(self):
         """Initialize flow field and sync objects to GPU."""
-        self._require_usable()
         self._assert_allocation_contract()
         # Validate the complete geometry before flags, populations or modules
         # change. Compact-list construction publishes no outputs on failure.
@@ -496,7 +478,6 @@ class Simulation:
         In EsoPull mode, the backing layout is decoded to physical DDF on
         GPU for the patched cells only, patched on host, then encoded back.
         """
-        self._require_usable()
         if not self._initialized:
             raise RuntimeError("Call initialize() before sync_bodies()")
 
@@ -592,7 +573,6 @@ class Simulation:
                 sensor) on GPU and reset the step accumulator before stepping.
             checkpoint_interval: Nonnegative integer; if >0, save every N steps.
         """
-        self._require_usable()
         if not self._initialized:
             raise RuntimeError("Call initialize() first")
         steps = operator.index(steps)
@@ -657,12 +637,10 @@ class Simulation:
     @context_bound
     def get_macroscopic(self) -> Dict[str, np.ndarray]:
         """Download DDF and return rho, ux, uy [, uz]."""
-        self._require_usable()
         return self.field.get_macroscopic(step_id=self.stepper.step_count)
 
     @context_bound
     def get_ddf(self) -> np.ndarray:
-        self._require_usable()
         self.field.download_ddf(step_id=self.stepper.step_count)
         return self.field.ddf.copy()
 
@@ -676,27 +654,23 @@ class Simulation:
 
         Accepted: omega, fx, fy, fz, n_objects.
         """
-        self._require_usable()
         self.field.update_params(**kwargs)
 
     # -- Snapshots -----------------------------------------------------------
     @context_bound
     def snapshot(self):
         """Snapshot the flow field; restore keeps the current clock and controls."""
-        self._require_usable()
         self.field.snapshot(step_id=self.stepper.step_count)
 
     @context_bound
     def restore(self):
         """Restore the saved flow field at the current streaming parity."""
-        self._require_usable()
         self.field.restore(step_id=self.stepper.step_count)
 
     # -- Checkpoint / Restore (HDF5) ----------------------------------------
     @context_bound
     def save_checkpoint(self, path: str = None):
         """Save full simulation state to an HDF5 file."""
-        self._require_usable()
         from .common.checkpoint import save_checkpoint
         if self.bodies.jets:
             raise NotImplementedError("Jets are not checkpointed yet")
@@ -706,7 +680,6 @@ class Simulation:
     @context_bound
     def load_checkpoint(self, path: str):
         """Restore simulation state from an HDF5 checkpoint."""
-        self._require_usable()
         from .common.checkpoint import load_checkpoint
         if not self._initialized:
             self.initialize()

tests/unit/test_jet_update_failure.py

@@ -1,149 +0,0 @@
-"""Jet amplitude update failure contract (host doubles only, no CUDA numerics).
-
-Both owners validate before any device write, commit host state only after the
-upload returns, and refuse every later call except close() after an uncertain
-device write.
-"""
-from types import SimpleNamespace
-
-import numpy as np
-import pytest
-
-pytest.importorskip("pycuda.driver")
-from CelerisLab import simulation as module
-from CelerisLab.body.jets import Jet, Radial, Sector
-from tests.unit.test_pinned_body_remap import ready
-from tests.unit.test_simulation_lifecycle import make_simulation
-
-BAD = (float("nan"), float("inf"), 1.)
-
-
-class Curved:
-    """Records uploads; ``fail`` raises once the write was attempted."""
-    def __init__(self):
-        self.writes, self.fail = [], False
-
-    def set_jet_amplitude(self, index, amplitude, stream):
-        self.writes.append((index, amplitude))
-        if self.fail:
-            raise RuntimeError("upload failed")
-
-
-def simulation(monkeypatch):
-    sim = make_simulation(monkeypatch)
-    jet = Jet(Sector((6., 5.), 0., .5, 4.), Radial((6., 5.)), "uniform", 1e-3)
-    sim._failed, sim._initialized = None, True
-    sim.bodies, sim.field = SimpleNamespace(jets=[jet]), SimpleNamespace(curved=Curved())
-    return sim, jet
-
-
-def test_simulation_invalid_input_writes_nothing_and_stays_usable(monkeypatch):
-    sim, jet = simulation(monkeypatch)
-    for amplitude in BAD:
-        with pytest.raises(ValueError):
-            sim.set_jet_amplitude(0, amplitude)
-    with pytest.raises(IndexError):
-        sim.set_jet_amplitude(1, 2e-3)
-    assert sim.field.curved.writes == [] and sim.bodies.jets[0] is jet and sim._failed is None
-    sim.set_jet_amplitude(0, 2e-3)  # retry after a rejected input
-    assert sim.field.curved.writes == [(0, 2e-3)] and sim.bodies.jets[0].amplitude == 2e-3
-    sim.close()
-
-
-def test_simulation_upload_failure_keeps_host_and_blocks_reuse(monkeypatch):
-    sim, jet = simulation(monkeypatch)
-    sim.field.curved.fail = True
-    with pytest.raises(RuntimeError, match="upload failed"):
-        sim.set_jet_amplitude(0, 2e-3)
-    assert sim.bodies.jets[0] is jet and sim._failed is not None
-    sim.field.curved.fail = False
-    for call in (lambda: sim.set_jet_amplitude(0, 2e-3), lambda: sim.run(1), sim.step,
-                 sim.sync_bodies, sim.initialize, sim.get_ddf, sim.get_macroscopic,
-                 lambda: sim.read_surface_exchange(0), lambda: sim.read_body(0),
-                 sim.read_bodies, sim.snapshot, sim.restore, sim.save_checkpoint,
-                 lambda: sim.load_checkpoint("x.h5"), lambda: sim.update_runtime_params(omega=1.)):
-        with pytest.raises(RuntimeError, match="Simulation failed"):
-            call()
-    assert sim.field.curved.writes == [(0, 2e-3)]
-    sim.close()  # cleanup still works
-    assert sim._closed and sim.ctx.is_closed
-
-
-def test_simulation_stream_creation_failure_fails_closed(monkeypatch):
-    sim, jet = simulation(monkeypatch)
-    created = []
-    def stream():
-        created.append(1)
-        raise RuntimeError("stream creation failed")
-    monkeypatch.setattr(module.cuda, "Stream", stream, raising=False)
-    sim._stream = None
-    with pytest.raises(RuntimeError, match="stream creation failed"):
-        sim.set_jet_amplitude(0, 2e-3)
-    assert sim.bodies.jets[0] is jet and sim._failed is not None
-    assert sim.field.curved.writes == [] and created == [1]
-    for call in (lambda: sim.stream, lambda: sim.set_jet_amplitude(0, 2e-3)):
-        with pytest.raises(RuntimeError, match="Simulation failed"):
-            call()
-    assert created == [1]  # the public stream property does not retry creation
-    sim.ctx.detach_failure = True
-    with pytest.raises(RuntimeError, match="detach failed"):
-        sim.close()
-    assert not sim._closed
-    sim.close()  # close stays retryable after the failure
-    assert sim._closed and sim.ctx.is_closed
-
-
-def test_simulation_before_initialize_commits_host_only(monkeypatch):
-    sim, _ = simulation(monkeypatch)
-    sim._initialized = False
-    sim.set_jet_amplitude(0, -2e-3)
-    assert sim.field.curved.writes == [] and sim.bodies.jets[0].amplitude == -2e-3
-    sim.close()
-
-
-def stepper_state(run):
-    boundary = run._level_boundaries[2]
-    return boundary.tables["surface_velocity"].copy(), boundary.jets, run._level_jets[2]
-
-
-def test_stepper_invalid_input_writes_nothing_and_stays_ready():
-    run, module, _, _, _ = ready()
-    try:
-        velocity, jets, level_jets = stepper_state(run)
-        module.cuda.memcpy_htod.reset_mock()
-        for args, kw, error in [((0, a), {"level": 2}, ValueError) for a in BAD] + [
-                ((1, .01), {"level": 2}, IndexError), ((0, .01), {"level": 3}, ValueError)]:
-            with pytest.raises(error):
-                run.set_jet_amplitude(*args, **kw)
-        module.cuda.memcpy_htod.assert_not_called()
-        np.testing.assert_array_equal(run._level_boundaries[2].tables["surface_velocity"], velocity)
-        assert (run._level_boundaries[2].jets, run._level_jets[2]) == (jets, level_jets)
-        assert run._status == "ready"
-        run.set_jet_amplitude(0, .017, level=2)
-        assert run._level_jets[2][0].amplitude == .017
-    finally:
-        run.close()
-
-
-@pytest.mark.parametrize("where", ["upload", "synchronize"])
-def test_stepper_device_failure_keeps_host_and_blocks_reuse(where):
-    run, module, _, _, _ = ready()
-    try:
-        velocity, jets, level_jets = stepper_state(run)
-        if where == "upload":
-            module.cuda.memcpy_htod.side_effect = RuntimeError("upload failed")
-        else:
-            run._stream.synchronize.side_effect = RuntimeError("upload failed")
-        with pytest.raises(RuntimeError, match="upload failed"):
-            run.set_jet_amplitude(0, .017, level=2)
-        np.testing.assert_array_equal(run._level_boundaries[2].tables["surface_velocity"], velocity)
-        assert (run._level_boundaries[2].jets, run._level_jets[2]) == (jets, level_jets)
-        assert run._status == "failed"
-        module.cuda.memcpy_htod.side_effect = None
-        run._stream.synchronize.side_effect = None
-        for call in (lambda: run.set_jet_amplitude(0, .017, level=2), run.step, run.download):
-            with pytest.raises(RuntimeError, match="failed"):
-                call()
-    finally:
-        run.close()
-    assert run._status == "closed"

tests/unit/test_jets.py

@@ -194,7 +194,6 @@ def test_public_surface_exchange_for_jet_preserves_aperture_at_zero_and_reverse(
     field, bodies = jet_case(device, [jet])
     sim = SimpleNamespace(bodies=bodies, field=field, _initialized=True,
                           stream=SimpleNamespace(synchronize=device.synchronize))
-    sim._require_usable = Simulation._require_usable.__get__(sim)
     cl = field.curved
     assert bodies.get(0).surface_actuation is None
     aperture, velocity = cl.aperture, cl.surface_velocity.copy()
@@ -219,7 +218,6 @@ def test_public_surface_exchange_keeps_legacy_and_passive_guards(device):
     bodies.sync_to_gpu(field)
     sim = SimpleNamespace(bodies=bodies, field=field,
                           stream=SimpleNamespace(synchronize=device.synchronize))
-    sim._require_usable = Simulation._require_usable.__get__(sim)
     for value in Simulation.read_surface_exchange(sim, 0).values():
         np.testing.assert_array_equal(value, 0.)
     field.curved.free_gpu_columns()

tests/unit/test_state_regressions.py

@@ -295,7 +295,6 @@ def test_passive_overlap_failure_keeps_live_state(device, entry, second_x):
                           _initialized=entry == "runtime_edit",
                           _assert_allocation_contract=lambda: None,
                           stream=SimpleNamespace(synchronize=device.synchronize))
-    sim._require_usable = Simulation._require_usable.__get__(sim)
     with pytest.raises(ValueError, match="active fluid receivers|unique cut-link writers"):
         if entry == "sync":
             bodies.sync_to_gpu(field)

tests/validation/multigrid/test_refinement_followup.py

@@ -20,7 +20,7 @@ from CelerisLab.lbm import refinement_stepper as implementation
 from CelerisLab.lbm.blocks import BlockLayout2D
 from test_refinement_gpu import (ROOT, POP_ATOL, MOMENT_ATOL, ref, postcollision,
                                  totals, LBMConfig, CudaContext, compiler,
-                                 PeriodicPatchStepper)
+                                 FixedPatchStepper)
 
 
 def scalar_interval(coarse, fine, bounds, slot=None):
@@ -123,7 +123,7 @@ class FaultGuardsCPU(unittest.TestCase):
                                                      refinements=[bounds], level_blocks=[(1, 1)] * 2)
 
     def fake_backend(self):
-        backend = PeriodicPatchStepper.__new__(PeriodicPatchStepper)
+        backend = FixedPatchStepper.__new__(FixedPatchStepper)
         layout = BlockLayout2D.build(1, 1, 1, 1, periodic=(False, False))
         backend._layouts = [layout, layout]  # blocked storage on both levels
         backend._ddf_shifting = False  # unshifted on every level, as _check_storage expects
@@ -175,7 +175,7 @@ class FaultGuardsCPU(unittest.TestCase):
         context = Mock(activate=nullcontext, sm_arch="sm_70")
         with patch.object(implementation, "HALO", 2):
             with self.assertRaisesRegex(RuntimeError, "four-cell"):
-                PeriodicPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)],
+                FixedPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)],
                                      level_blocks=[(16, 16), (24, 24)])
         p = implementation.FixedPatch2D.from_config(cfg, (4, 4, 12, 12))
         from CelerisLab.lbm import hierarchy
@@ -187,11 +187,11 @@ class FaultGuardsCPU(unittest.TestCase):
         with patch.object(cuda, "Stream"), patch.object(cuda, "mem_get_info", return_value=(1 << 40, 1 << 40)), bad, patch.object(cuda, "mem_alloc") as alloc, \
                 patch.object(cuda, "memcpy_htod") as upload:
             with self.assertRaisesRegex(RuntimeError, "config chain is inconsistent"):
-                PeriodicPatchStepper(cfg, context=context, refinements=[p.bounds],
+                FixedPatchStepper(cfg, context=context, refinements=[p.bounds],
                                      level_blocks=[(16, 16), (24, 24)])
             with patch.object(hierarchy, "_check_chain"), \
                     self.assertRaisesRegex(RuntimeError, "omega/tau"):
-                PeriodicPatchStepper(cfg, context=context, refinements=[p.bounds],
+                FixedPatchStepper(cfg, context=context, refinements=[p.bounds],
                                      level_blocks=[(16, 16), (24, 24)])
             alloc.assert_not_called()
             upload.assert_not_called()
@@ -202,7 +202,7 @@ class FaultGuardsCPU(unittest.TestCase):
                 patch.object(compiler, "load_module", return_value=module), \
                 patch.object(cuda, "memcpy_htod") as upload:
             with self.assertRaisesRegex(RuntimeError, "layout mismatch"):
-                PeriodicPatchStepper(cfg, context=context, refinements=[p.bounds],
+                FixedPatchStepper(cfg, context=context, refinements=[p.bounds],
                                      level_blocks=[(16, 16), (24, 24)])
             upload.assert_not_called()
 
@@ -348,7 +348,7 @@ class NormalBuildGPU(unittest.TestCase):
         state = ref.State(*(a * (1 + 1e-3*rng.standard_normal(a.shape))
                             for a in (initial.coarse_f, initial.fine_f)))
         max_pop = max_drift = max_moment = 0.0
-        with CudaContext(0) as context, PeriodicPatchStepper(
+        with CudaContext(0) as context, FixedPatchStepper(
                 LBMConfig(nx=16, ny=16, viscosity=.1), context=context,
                 refinements=[(4, 4, 12, 12)], level_blocks=[(16, 16), (24, 24)]) as backend:
             backend.initialize(*postcollision(state, spec, maps))
@@ -381,7 +381,7 @@ class NormalBuildGPU(unittest.TestCase):
         fine_mask[4:-4, 4:-4] = True
         initial[1][:, ~fine_mask] = np.nan
         expected = scalar_interval(*[a.astype(np.float64) for a in initial], bounds)
-        with CudaContext(0) as context, PeriodicPatchStepper(cfg, context=context, refinements=[bounds],
+        with CudaContext(0) as context, FixedPatchStepper(cfg, context=context, refinements=[bounds],
                                                              level_blocks=[(13, 17), (14, 16)]) as backend:
             self.assertEqual(backend.patch.fine_shape, (14, 16))
             p = backend.patch

tests/validation/multigrid/test_refinement_gpu.py

@@ -22,7 +22,7 @@ import CelerisLab
 from CelerisLab.config import LBMConfig
 from CelerisLab.cuda import compiler
 from CelerisLab.cuda.context import CudaContext
-from CelerisLab.lbm.refinement_stepper import FixedPatchStepper, PeriodicPatchStepper
+from CelerisLab.lbm.refinement_stepper import FixedPatchStepper
 
 ROOT = Path(__file__).resolve().parents[3]
 POP_ATOL = 3e-6
@@ -124,7 +124,7 @@ class CoupledGPU(unittest.TestCase):
                               "wrong-phase controls PASS", flush=True)
 
     def test_cleanup_attempts_every_allocation(self):
-        backend = PeriodicPatchStepper.__new__(PeriodicPatchStepper)
+        backend = FixedPatchStepper.__new__(FixedPatchStepper)
         backend.ctx = Mock(activate=nullcontext)
         backend._lock = RLock()
         backend._status = "failed"
@@ -146,7 +146,7 @@ class CoupledGPU(unittest.TestCase):
         spec = ref.make_spec(collision="srt")
         maps = ref.build_maps(spec)
         with CudaContext(0) as context:
-            with PeriodicPatchStepper(LBMConfig(nx=16, ny=16, viscosity=.1),
+            with FixedPatchStepper(LBMConfig(nx=16, ny=16, viscosity=.1),
                                       context=context, refinements=[(4, 4, 12, 12)],
                                       level_blocks=[(16, 16), (24, 24)]) as backend:
                 backend.initialize(*postcollision(ref.make_state(spec), spec, maps))
@@ -223,7 +223,7 @@ class CoupledGPU(unittest.TestCase):
         maps = ref.build_maps(spec)
         cfg = LBMConfig(nx=16, ny=16, viscosity=.1)
         with CudaContext(0) as context:
-            with PeriodicPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)],
+            with FixedPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)],
                                       level_blocks=[(16, 16), (24, 24)]) as backend:
                 self.eight_steps(backend, spec, maps)
                 with patch.object(backend._pairs[0], "explode", side_effect=RuntimeError("injected launch failure")):