tests: restore the negative checks masked by stale fixtures (WP-B groups B-E)

Test-side only; no production, manifest or pin change. Group A identity
checks (test_source_pin and the jets.py pins) are unchanged and stay
failing as recorded.

B test_refined_dfg: receipt/plan fixtures load the frozen manifest JSON
  that verify_source returns for a matching tree (frozen_manifest), and
  the two manifest-selection assertions call verify_source with only its
  working-tree hash comparison neutralised (selected_manifest), so the
  malformed/collision/observation-mode/checkout receipt checks run again.
  test_source_pin remains the single identity check.
C test_channel_root: int(owner)-1 (uint64-int became float on NumPy 1);
  test_shifted_storage: FP32 NaN fill so the arrays stay FP32. Both reach
  the intended immutable/representation/FP32/density checks.
D test_block_stepper fake gets _ddf_shifting; test_fine_surface_gpu sets
  _boundary_hosts/_level_jets instead of the read-only fine_boundary view;
  test_refinement_followup fake_backend sets _layouts/_ddf_shifting/
  _level_cfgs instead of the read-only fine_layout view (as reviewed in
  32da2d73).
E test_kernel_contracts_reject_before_upload: an inconsistent pair tau is
  now first rejected by the hierarchy chain check; the test asserts that
  rejection, then bypasses _check_chain to prove the per-level omega/tau
  guard still rejects, and asserts no mem_alloc/memcpy_htod in either case.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -112,8 +112,9 @@ from CelerisLab.lbm.refinement_stepper import FixedPatchStepper
 cfg = LBMConfig(nx=32, ny=24, viscosity=.1)
 body = SimObject(0, geometry=CircleGeometry(16.0, 12.0, 2.15), center=(16.0, 12.0), radius=2.15,
                  surface_actuation=SurfaceActuation(0.7, 0.85, 0.002))  # angle, half-width, speed
-with CudaContext(0) as ctx, FixedPatchStepper(cfg, (8, 6, 24, 18), context=ctx,
-                                              fine_objects=[body], fine_block=(16, 20)) as run:
+with CudaContext(0) as ctx, FixedPatchStepper(cfg, context=ctx, refinements=[(8, 6, 24, 18)],
+                                              level_blocks=[None, (16, 20)],
+                                              level_objects=[(), (body,)]) as run:
     rest = np.asarray(compute_feq_d2q9(1.0, 0.0, 0.0), np.float32)[:, None, None]
     # (9, ny, nx) postcollision populations per level; non-leaf cells are discarded.
     run.initialize(np.broadcast_to(rest, (9, *run.patch.coarse_shape)),
@@ -124,8 +125,8 @@ with CudaContext(0) as ctx, FixedPatchStepper(cfg, (8, 6, 24, 18), context=ctx,
 
 Scope and limits:
 - The examples below use D2Q9, SRT, FP32, double buffer, unshifted, no LES or
-  forcing. Fixed 2:1 hierarchies can use level lists of arbitrary depth; the
-  legacy two/three-level forms are shown below.
+  forcing. Fixed 2:1 hierarchies use level lists of arbitrary depth; two- and
+  three-level examples below use that same constructor.
 - `coarse_boundary="periodic"` (default) or `"slot_reservoir"` (bottom slot, top
   reservoir; patch needs `y0 >= 4`, `y1 <= ny-4`). Periodic mode ignores the wall/slot config fields.
 - Object centers/radii use the coarse **cell-edge** frame (cell `I` spans `[I, I+1)`),
@@ -133,50 +134,51 @@ Scope and limits:
 - Bodies must be stationary circles whose whole boundary stencil lies in the fine
   active region, clear of the coarse/fine transfer cells; violations are rejected
   before any GPU allocation.
-- `fine_block=(by, bx)` stores the fine level in fixed-size blocks; `by`/`bx` must
+- `level_blocks=[None, (by, bx)]` stores the fine level in fixed-size blocks; `by`/`bx` must
   divide the WHOLE fine allocation, i.e. `2*(y1-y0)+8` by `2*(x1-x0)+8` including the
   four-cell ghost band. It gives results identical to dense storage and is
   infrastructure for future block AMR, not a speedup.
 - Several regions: pass a sequence of `(x0, y0, x1, y1)` rectangles as
-  `bounds`, with both `fine_block` and `base_block`. Transfers are built once
+  `refinements[0]`, with both levels blocked (`level_blocks`). Transfers are built once
   from their union; adjacent, overlapping and concave unions are accepted when
   their actual dependencies close. There is no fixed rectangle-gap rule.
   The fine level is then one level-wide grid `(2*ny, 2*nx)`:
   `run.patch.fine_shape` gives it, `initialize`/`download` use it, and only the
   grid-aligned tiles intersecting the union plus its four-cell ghost band are stored.
   Block sizes must divide the level-wide grid; rectangle edges need not align
-  with tiles. Order of rectangles does not matter. `fine_objects`/`jets` work
+  with tiles. Order of rectangles does not matter. L1 bodies/Jets (`level_objects[1]`/`level_jets[1]`) work
   as for one patch: each circle (same coarse cell-edge frame) must lie wholly
   inside the union's active region with
   its boundary stencil clear of transfer cells; a jet may not select links of two
   different bodies, even across regions. Wall-touching patches remain unsupported.
-  For nesting, use the level lists or legacy child forms below.
+  For nesting, add further `refinements` entries as shown below.
 
   ```python
   cfg = LBMConfig(nx=32, ny=16, viscosity=.1)
   rest = np.asarray(compute_feq_d2q9(1.0, 0.0, 0.0), np.float32)[:, None, None]
   with CudaContext(0) as ctx, FixedPatchStepper(
-          cfg, ((4, 4, 12, 12), (16, 4, 24, 12)), context=ctx,
-          fine_block=(4, 4), base_block=(4, 4)) as run:
+          cfg, context=ctx, refinements=[((4, 4, 12, 12), (16, 4, 24, 12))],
+          level_blocks=[(4, 4), (4, 4)]) as run:
       run.initialize(np.broadcast_to(rest, (9, *run.patch.coarse_shape)),
                      np.broadcast_to(rest, (9, *run.patch.fine_shape)))  # (9, 32, 64)
       run.step(32)
       coarse_g, fine_g = run.download()  # coarse: NaN on every covered cell;
                                          # fine: NaN on every non-ACTIVE cell
   ```
-- Legacy three-level scalar chain: add `child=(x0, y0, x1, y1)` in
-  **L1 window cells** (the patch's fine grid including its 4-cell ghost band) and
-  `child_block`, with `fine_block` and `base_block`. L2 must sit inside L1's
-  ACTIVE cells, away from L1's ghost band and transfer footprint (checked before
-  any GPU allocation). `initialize` and `download` take/return three arrays; each
-  level is NaN on its non-ACTIVE (and child-covered) cells. One coarse step = 2 L1
-  steps = 4 L2 steps. One L1 patch only. Optional stationary circles and Jets
-  live on L2 via `child_objects` and `child_jets`; `fine_objects`/`jets` retain
-  their L1 meaning and must be empty in this mode. All object and Jet geometry
-  uses the **L0 edge frame**, not the child bounds' L1 window frame. L2 has
-  dx=dt=0.25, so prescribed lattice velocity is unchanged. Each whole body and
-  its BFL stencil must be inside L2 ACTIVE cells, outside the transfer footprint.
-  A Jet may select one physical body across multiple blocks, never two bodies.
+- Three-level nested windows: pass two scalar rectangles in `refinements` —
+  L1 in L0 cells, L2 in **L1 window cells** (the parent's fine grid including its
+  4-cell ghost band) — plus all three `level_blocks` entries. L2 must sit inside
+  L1's ACTIVE cells, away from L1's ghost band and transfer footprint (checked
+  before any GPU allocation). `initialize` and `download` take/return three
+  arrays; each level is NaN on its non-ACTIVE (and child-covered) cells. One
+  coarse step = 2 L1 steps = 4 L2 steps. One L1 window only in this scalar
+  chain. Optional stationary circles and Jets live on L2 via `level_objects[2]`
+  and `level_jets[2]`; L1 bodies/Jets retain their L1 meaning and must be empty
+  in this mode. All object and Jet geometry uses the **L0 edge frame**, not the
+  child bounds' L1 window frame. L2 has dx=dt=0.25, so prescribed lattice
+  velocity is unchanged. Each whole body and its BFL stencil must be inside L2
+  ACTIVE cells, outside the transfer footprint. A Jet may select one physical
+  body across multiple blocks, never two bodies.
 
   ```python
   from CelerisLab.body.geometry.circle import CircleGeometry
@@ -188,9 +190,9 @@ Scope and limits:
   jet = Jet(Tube((6.5, 8.), 0., 3., .3), Parallel(0.), amplitude=.002)
   rest = np.asarray(compute_feq_d2q9(1.0, 0.0, 0.0), np.float32)[:, None, None]
   with CudaContext(0) as ctx, FixedPatchStepper(
-          cfg, (4, 4, 12, 12), context=ctx, fine_block=(4, 4), base_block=(4, 4),
-          child=(8, 8, 16, 16), child_block=(4, 4),
-          child_objects=[body], child_jets=[jet]) as run:
+          cfg, context=ctx, refinements=[(4, 4, 12, 12), (8, 8, 16, 16)],
+          level_blocks=[(4, 4)] * 3, level_objects=[(), (), (body,)],
+          level_jets=[(), (), (jet,)]) as run:
       shapes = (run.patch.coarse_shape, run.patch.fine_shape, run.child_patch.fine_shape)
       run.initialize(*(np.broadcast_to(rest, (9, *s)) for s in shapes))  # 16², 24², 24²
       run.step(4)
@@ -198,16 +200,16 @@ Scope and limits:
       run.step(4)
       coarse_g, l1_g, l2_g = run.download()  # solids/covered/nonleaves are NaN
   ```
-- Level lists: `refinements[l]` describes level `l+1` in allocated level-`l`
-  integer cells; use a rectangle list for a union, or a scalar rectangle for a
-  single window (a scalar child requires a scalar parent). `level_blocks`,
-  `level_objects` and `level_jets` each have one entry per level, including L0.
-  These lists are mutually exclusive with the legacy patch keywords. Three or
-  more levels require all-blocked storage and bodies/Jets only on the finest
-  level. Every adjacent pair must preserve inherited ACTIVE coverage, valid
-  donors/receivers, surviving pulls and the upstream transfer footprint.
-  Level `l` takes `2**l` steps per base interval. This describes implemented
-  topology and scheduling, not accuracy or convergence qualification.
+- Level lists (the only constructor): `refinements[l]` describes level `l+1`
+  in allocated level-`l` integer cells; use a rectangle list for a union, or a
+  scalar rectangle for a single window (a scalar child requires a scalar
+  parent). `level_blocks`, `level_objects` and `level_jets` each have one entry
+  per level, including L0. Three or more levels require all-blocked storage and
+  bodies/Jets only on the finest level. Every adjacent pair must preserve
+  inherited ACTIVE coverage, valid donors/receivers, surviving pulls and the
+  upstream transfer footprint. Level `l` takes `2**l` steps per base interval.
+  This describes implemented topology and scheduling, not accuracy or
+  convergence qualification.
 - Blocked body levels can enable `observe_raw_exchange=True` and call
   `read_raw_exchange(body_id, level=...)` after a completed base interval.
   It reduces unique cut-link observations into wall/aperture/total force,

docs/development/root_channel_candidate.md

@@ -1,6 +1,6 @@
 # Blocked AMR root channel increment
 
-Opt in with `FixedPatchStepper(..., coarse_boundary="channel", base_block=(by,bx), fine_block=(fy,fx))`, or the existing level-list form. Every level must be blocked. The supported boundary is the existing uniform D2Q9/SRT/FP32 double-buffer channel: local Zou-He west inlet, pressure-NEQ east outlet, stationary halfway bounce-back y walls. Uniform and parabolic inlet profiles and shifted/unshifted storage are supported; the existing configuration guards still reject MRT/LES and incompatible storage. This does not change the external DFG MRT reference.
+Opt in with `FixedPatchStepper(..., coarse_boundary="channel", refinements=[bounds], level_blocks=[(by,bx), (fy,fx)])`. Every level must be blocked. The supported boundary is the existing uniform D2Q9/SRT/FP32 double-buffer channel: local Zou-He west inlet, pressure-NEQ east outlet, stationary halfway bounce-back y walls. Uniform and parabolic inlet profiles and shifted/unshifted storage are supported; the existing configuration guards still reject MRT/LES and incompatible storage. This does not change the external DFG MRT reference.
 
 `step/block_channel.cu` is a small root-only kernel. Fine kernels, transfer kernels and recursive hop scheduling are unchanged. Global coordinates and the global profile height/velocity are separate from block-local storage strides. Corner ownership and collision phases match `OneStep`:
 

docs/fixed_three_level_multipatch.md

@@ -1,8 +1,8 @@
 # Fixed three-level rectangle unions
 
-This page describes the legacy three-level entry point of `FixedPatchStepper`,
-with rectangle unions on either adjacent pair. The `refinements` level-list
-entry point also supports arbitrary depth; three or more levels require
+This page describes three-level `FixedPatchStepper` setups built from the
+`refinements` level list, with rectangle unions on either adjacent pair. The
+same constructor supports arbitrary depth; three or more levels require
 all-blocked storage and bodies/Jets only on the finest level. This is not
 general AMR: there is no per-region timestep, moving geometry, automatic
 dynamic refinement or L1 body support in the three-level form.
@@ -12,15 +12,15 @@ No CUDA kernel changes are involved.
 
 ## Explicit coordinate frames
 
-Keep the existing scalar `child=(x0,y0,x1,y1)` for a single scalar parent patch.
-Its coordinates retain their original meaning: half-open integer indices in the
-allocated L1 window, including its ghost band.
+For a single scalar parent patch, pass a scalar rectangle as `refinements[1]`:
+`(x0,y0,x1,y1)` in half-open integer indices of the allocated L1 window,
+including its ghost band.
 
-The new keyword `child_rectangles_in_parent=[...]` is mutually exclusive with
-`child`. It accepts a scalar or a set parent and interprets every rectangle in
-the actual allocated L1 array, including ghost bands and holes. It never infers
-region-local coordinates. The physical root cell edge corresponding to an L1
-index `(x,y)` is `parent.fine_origin + (x,y)/2`:
+A rectangle list as `refinements[1]` accepts a scalar or a set parent and
+interprets every rectangle in the actual allocated L1 array, including ghost
+bands and holes. It never infers region-local coordinates. The physical root
+cell edge corresponding to an L1 index `(x,y)` is
+`parent.fine_origin + (x,y)/2`:
 
 - A scalar L1 parent has a shifted window origin.
 - A set L1 parent has origin `(0,0)` and public shape `(2*ny,2*nx)`.
@@ -47,9 +47,9 @@ tile edges.
 
 ```python
 run = FixedPatchStepper(
-    cfg, [(4, 4, 20, 28), (24, 4, 44, 28)], context=ctx,
-    base_block=(4, 4), fine_block=(4, 4), child_block=(4, 4),
-    child_rectangles_in_parent=[(16, 16, 32, 40), (56, 16, 80, 40)],
+    cfg, context=ctx,
+    refinements=[[(4, 4, 20, 28), (24, 4, 44, 28)], [(16, 16, 32, 40), (56, 16, 80, 40)]],
+    level_blocks=[(4, 4)] * 3,
 )
 ```
 
@@ -57,7 +57,7 @@ This example uses a 48x32 root. `initialize` and `download` use three Q-major
 dense arrays. Public arrays and masks still scale with the full allocated
 extent; sparse device buffers do not remove that host-memory limit.
 
-Stationary whole-circle `child_objects` and `child_jets` use root edge
+Stationary whole-circle L2 bodies and Jets (`level_objects[2]`, `level_jets[2]`) use root edge
 coordinates and a single L2 boundary object. Body IDs are physical object-list
 positions, not region IDs or caller `obj_id`. Complete boundary stencils must
 avoid the transfer footprint. Change a child Jet with

examples/fixed_patch_circle.py

@@ -90,8 +90,8 @@ def main():
     # The caller owns the CUDA context; the stepper must be closed first (the
     # nested with-statement does that).
     with CudaContext(0) as context, FixedPatchStepper(
-            cfg, BOUNDS, context=context, coarse_boundary=args.mode,
-            fine_objects=[body], fine_block=fine_block) as run:
+            cfg, context=context, coarse_boundary=args.mode, refinements=[BOUNDS],
+            level_blocks=[None, fine_block], level_objects=[(), (body,)]) as run:
         p = run.patch
         # Rest equilibrium is already postcollision G, so no initial collision is
         # needed. Non-leaf entries (covered, ghost, solid) are discarded by initialize.

examples/fixed_patch_jet.py

@@ -148,8 +148,8 @@ def main():
                   samples=[], status='running', last_synchronized_coarse_step=0)
     start, run = time.monotonic(), None
     try:
-        with CudaContext(0) as context, FixedPatchStepper(cfg, BOUNDS, context=context,
-                coarse_boundary='slot_reservoir') as run:
+        with CudaContext(0) as context, FixedPatchStepper(cfg, context=context,
+                coarse_boundary='slot_reservoir', refinements=[BOUNDS]) as run:
             p = run.patch
             masks = [np.ones(p.coarse_shape, bool), p.fine_kind == ACTIVE]
             masks[0][[0, -1]] = False

examples/fixed_periodic_patch.py

@@ -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, (4, 4, 12, 12), context=context) as run:
+    with CudaContext(0) as context, PeriodicPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)]) as run:
         p = run.patch
         coarse = shear_equilibrium(p.coarse_shape, (0, 0), 1.0, cfg.ny)
         fine = shear_equilibrium(p.fine_shape, p.fine_origin, .5, cfg.ny)

src/CelerisLab/body/jets.py

@@ -207,19 +207,30 @@ def surface_link_velocity(objects, cfg, flags, fluid_idx, dir, body_id, rx, ry,
                           jets=(), hits=None, *, _shifted_blocked=False):
     """Per-link prescribed surface velocity (n, 2) FP32 and aperture mask.
 
+    See _surface_links, which also returns the unit-amplitude jet shapes.
+    """
+    return _surface_links(objects, cfg, flags, fluid_idx, dir, body_id, rx, ry, jets, hits,
+                          _shifted_blocked=_shifted_blocked)[:2]
+
+
+def _surface_links(objects, cfg, flags, fluid_idx, dir, body_id, rx, ry,
+                   jets=(), hits=None, *, _shifted_blocked=False):
+    """(velocity, aperture, jet shape, jet id); the last two are None without jets.
+
     Host-only and storage-neutral: rows follow the given physical cut-link
-    order. Returns (None, None) when neither an object carries surface
+    order. Returns all None when neither an object carries surface
     actuation nor a jet is given. Jets need true FP64 ``hits`` (n, 2) and may
     not share a link with each other or with a legacy aperture.
     Shifted storage is privately enabled only by the all-blocked stepper.
     """
     enabled = [obj for obj in objects if obj.surface_actuation is not None]
     if not enabled and not jets:
-        return None, None
+        return None, None, None, None
     from .preprocess.flag_overlay import validate_cut_link_ownership
     validate_cut_link_ownership(flags, fluid_idx, dir, cfg.nq)
     surface_velocity = np.zeros((len(dir), 2), np.float32)
     surface_aperture = np.zeros(len(dir), bool)
+    shape = jet_id = None
     for obj in enabled:
         obj.validate_surface_actuation(cfg)
         selected = body_id == obj.obj_id
@@ -252,4 +263,4 @@ def surface_link_velocity(objects, cfg, flags, fluid_idx, dir, body_id, rx, ry,
             raise ValueError("Jet overlaps a SurfaceActuation aperture")
         surface_velocity[driven] = jet_link_velocity(jets, shape, jet_id)[driven]
         surface_aperture |= driven
-    return surface_velocity, surface_aperture
+    return surface_velocity, surface_aperture, shape, jet_id

src/CelerisLab/lbm/curved_links.py

@@ -94,12 +94,10 @@ class CurvedLinkSoA:
         """
         self.surface_velocity = self.aperture = None
         self.jets, self.jet_shape, self.jet_id = tuple(jets), None, None
-        self.surface_velocity, self.aperture = surface_link_velocity(
+        from ..body.jets import _surface_links
+        self.surface_velocity, self.aperture, self.jet_shape, self.jet_id = _surface_links(
             objects, cfg, flags, self.fluid_idx, self.dir, self.body_id, self.rx, self.ry,
             jets=self.jets, hits=hits)
-        if self.jets:
-            from ..body.jets import jet_link_shapes
-            self.jet_shape, self.jet_id = jet_link_shapes(self.jets, hits)
 
     def set_jet_amplitude(self, index, amplitude, stream=None):
         """Rewrite jet rows from cached shapes; re-upload only the velocity column.

src/CelerisLab/lbm/kernels/blocks.cu

@@ -168,21 +168,15 @@ extern "C" __global__ void BlockStep(const fpxx* in, fpxx* out, unsigned int hal
         stream_pull_load(k, f, in + base, j);
         if (cell_kind == KIND_ACTIVE) {
             if (d_block_wall.nx != 0) {
-                const unsigned int bx = NX - 2 * halo, by = NY - 2 * halo;
-                const unsigned int nbx = d_block_wall.nx / bx;
-                const unsigned int gx = (blockIdx.z % nbx) * bx + x - halo;
-                const unsigned int gy = (blockIdx.z / nbx) * by + y - halo;
+                unsigned int gx, gy;
+                block_global_xy(x, y, halo, d_block_wall.nx, gx, gy);
                 if (gy == 1)
                     reconstruct_bottom_velocity(f, 0.0f, bottom_wall_normal_velocity(
                         gx, d_block_wall.nx, d_block_wall.slot_width, d_block_wall.amplitude));
                 else if (gy == d_block_wall.ny - 2) reconstruct_top_reservoir(f, RHO);
             }
 #if COLLISION_MODEL == 2
-            // Uniform MRT sequence (collide_dispatch, zero forcing); SRT path below unchanged.
-            float rho, ux, uy;
-            compute_rho_u(f, rho, ux, uy);
-            collide_mrt_no_force(f, rho, ux, uy,
-                fminf(OMEGA_COLLISION_MAX, fmaxf(OMEGA_COLLISION_MIN, d_params.omega)));
+            collide_mrt_unforced(f);  // SRT path below unchanged.
 #else
             float rho, ux, uy, feq[NQ];
             compute_rho_u(f, rho, ux, uy);

src/CelerisLab/lbm/kernels/core/layout.cuh

@@ -53,6 +53,18 @@ __device__ __forceinline__ void index_from_thread(unsigned int& x,
     k = (unsigned long)y * NX + x;
 }
 
+// Global cell of window cell (x, y) in block blockIdx.z of a row-major,
+// full-domain block layout domain_nx cells wide. NX/NY are the local strides.
+__device__ __forceinline__ void block_global_xy(unsigned int x, unsigned int y,
+                                                unsigned int halo, unsigned int domain_nx,
+                                                unsigned int& gx, unsigned int& gy)
+{
+    const unsigned int bx = NX - 2 * halo, by = NY - 2 * halo;
+    const unsigned int nbx = domain_nx / bx;
+    gx = (blockIdx.z % nbx) * bx + x - halo;
+    gy = (blockIdx.z / nbx) * by + y - halo;
+}
+
 // ---------------------------------------------------------------------------
 // Neighbor list (periodic BCs via modular arithmetic)
 // ---------------------------------------------------------------------------

src/CelerisLab/lbm/kernels/operators/collision_mrt.cuh

@@ -114,6 +114,16 @@ __device__ __forceinline__ void collide_mrt_no_force(float* __restrict__ g,
     collide_mrt(g, rho, ux, uy, Fin, omega);
 }
 
+// Unforced MRT with the clamped device omega, as in collide_dispatch with zero
+// forcing. Shared by the blocked, channel-root and dense-patch collisions.
+__device__ __forceinline__ void collide_mrt_unforced(float* __restrict__ g)
+{
+    float rho, ux, uy;
+    compute_rho_u(g, rho, ux, uy);
+    collide_mrt_no_force(g, rho, ux, uy,
+        fminf(OMEGA_COLLISION_MAX, fmaxf(OMEGA_COLLISION_MIN, d_params.omega)));
+}
+
 #elif LATTICE_MODEL == LATTICE_D3Q19
 
 __device__ __forceinline__ void collide_mrt(float* __restrict__ g,

src/CelerisLab/lbm/kernels/refinement.cu

@@ -37,10 +37,7 @@ __device__ unsigned int incoming_counts[NQ * TOTAL_CELLS];
 
 __device__ __forceinline__ void patch_collide(float* f, unsigned long k) {
 #if COLLISION_MODEL == 2
-    float rho, ux, uy;
-    compute_rho_u(f, rho, ux, uy);
-    collide_mrt_no_force(f, rho, ux, uy,
-        fminf(OMEGA_COLLISION_MAX, fmaxf(OMEGA_COLLISION_MIN, d_params.omega)));
+    collide_mrt_unforced(f);
 #else
     float rho, ux, uy, feq[NQ];
     compute_rho_u(f, rho, ux, uy);

src/CelerisLab/lbm/kernels/step/block_channel.cu

@@ -15,10 +15,8 @@ extern "C" __global__ void BlockChannelStep(
     unsigned int x, y; unsigned long k;
     index_from_thread(x, y, k);
     if (x < halo || y < halo || x >= NX - halo || y >= NY - halo) return;
-    const unsigned int bx = NX - 2 * halo, by = NY - 2 * halo;
-    const unsigned int nbx = d_block_channel.nx / bx;
-    const unsigned int gx = (blockIdx.z % nbx) * bx + x - halo;
-    const unsigned int gy = (blockIdx.z / nbx) * by + y - halo;
+    unsigned int gx, gy;
+    block_global_xy(x, y, halo, d_block_channel.nx, gx, gy);
     const unsigned long base = (unsigned long)blockIdx.z * NQ * TOTAL_CELLS;
     const unsigned long cell = (unsigned long)blockIdx.z * TOTAL_CELLS + k;
     float f[NQ];
@@ -55,11 +53,7 @@ extern "C" __global__ void BlockChannelStep(
         }
         if (!wall && !outlet) {
 #if COLLISION_MODEL == 2
-            // Match uniform MRT arithmetic (collide_dispatch, zero forcing).
-            float rho, ux, uy;
-            compute_rho_u(f, rho, ux, uy);
-            collide_mrt_no_force(f, rho, ux, uy,
-                fminf(OMEGA_COLLISION_MAX, fmaxf(OMEGA_COLLISION_MIN, d_params.omega)));
+            collide_mrt_unforced(f);
 #else
             // Match uniform SRT arithmetic, including its shifted equilibrium path.
             float rho, ux, uy, feq[NQ], forcing[NQ] = {};

src/CelerisLab/lbm/refinement_stepper.py

@@ -65,52 +65,8 @@ def _level_name(level):
     return ("base", "fine", "child")[level] if level < 3 else f"level {level}"
 
 
-def _legacy_levels(bounds, *, fine_block, base_block, child, child_block, child_rectangles_in_parent,
-                   fine_objects, jets, child_objects, child_jets):
-    """Normalise the original two/three-level keywords to per-level lists (original errors)."""
-    if child is not None and child_rectangles_in_parent is not None:
-        raise ValueError("child and child_rectangles_in_parent are mutually exclusive")
-    nested = child is not None or child_rectangles_in_parent is not None
-    bounds = tuple(bounds)
-    if not is_rectangle(bounds) and (fine_block is None or base_block is None):
-        raise ValueError("several patches require fine_block and base_block")
-    fine_objects, jets = tuple(fine_objects), tuple(jets)
-    child_objects, child_jets = tuple(child_objects), tuple(child_jets)
-    if not nested and (child_objects or child_jets):
-        raise ValueError("child_objects/child_jets require a nested child")
-    if base_block is not None and fine_block is None:
-        raise ValueError("base_block requires fine_block")
-    refinements, blocks = [bounds], [base_block, fine_block]
-    objects, level_jets = [(), fine_objects], [(), jets]
-    if nested:
-        if child is not None and not is_rectangle(bounds):
-            raise ValueError("scalar child requires one parent patch; use child_rectangles_in_parent")
-        if fine_block is None or base_block is None or child_block is None:
-            raise ValueError("a nested child needs fine_block, base_block and child_block")
-        if fine_objects or jets:
-            raise ValueError("a nested child supports bodies/Jets only on L2; use child_objects/child_jets")
-        refinements.append(tuple(child) if child is not None else tuple(child_rectangles_in_parent))
-        blocks.append(child_block)
-        objects.append(child_objects)
-        level_jets.append(child_jets)
-    return refinements, blocks, objects, level_jets
-
-
-def _initial_levels(level_g, coarse_g, fine_g, child_g):
-    """One tuple of per-level arrays from initialize()'s positional or legacy named form."""
-    if coarse_g is None and fine_g is None:
-        if child_g is not None and len(level_g) != 2:
-            raise TypeError("child_g needs exactly the coarse and fine arrays before it")
-        return tuple(level_g) + (() if child_g is None else (child_g,))
-    if level_g:
-        raise TypeError("pass level arrays positionally or as coarse_g/fine_g/child_g, not both")
-    if coarse_g is None or fine_g is None:
-        raise TypeError("coarse_g and fine_g are both required in the named form")
-    return (coarse_g, fine_g) + (() if child_g is None else (child_g,))
-
-
 def _check_levels(refinements, blocks, objects, jets):
-    """Candidate limits shared by the list and the legacy entry points."""
+    """Candidate limits of the level lists, checked before any device work."""
     depth = len(refinements) + 1
     if depth < 2:
         raise ValueError("at least one refinement level is required")
@@ -119,13 +75,13 @@ def _check_levels(refinements, blocks, objects, jets):
             raise ValueError(f"{name} needs one entry per level ({depth})")
     for level, block in enumerate(blocks):
         if block is not None and len(block) != 2:
-            raise ValueError(f"{_level_name(level)}_block must be (by, bx)")
+            raise ValueError(f"level_blocks[{level}] must be (by, bx)")
     if objects[0] or jets[0]:
         raise ValueError("base-level bodies/Jets are not supported")
     if any(blocks[level - 1] is not None and blocks[level] is None for level in range(1, depth)):
         raise ValueError("a blocked level requires blocked refined levels below it")
     if not is_rectangle(refinements[0]) and (blocks[0] is None or blocks[1] is None):
-        raise ValueError("several patches require fine_block and base_block")
+        raise ValueError("several L1 patches require level_blocks[0] and level_blocks[1]")
     if depth > 2:
         if any(block is None for block in blocks):
             raise ValueError("three or more levels must all be blocked")
@@ -134,7 +90,14 @@ def _check_levels(refinements, blocks, objects, jets):
 
 
 class FixedPatchStepper:
-    """D2Q9/SRT/FP32, one unforced internal 2:1 patch in an x-periodic box.
+    """D2Q9 SRT/MRT FP32 fixed 2:1 refinement hierarchy, built from level lists.
+
+    ``refinements[l]`` gives level l+1 in level-l integer cells: one rectangle
+    (x0, y0, x1, y1) (FixedPatch2D, a fine window with its own origin) or a
+    sequence of rectangles (FixedPatchSet2D, a dependency-validated union on one
+    level-wide grid, public fine arrays (2*ny, 2*nx), NaN outside ACTIVE cells);
+    see lbm.hierarchy. ``level_blocks``, ``level_objects`` and ``level_jets``
+    hold one entry per level, L0 included (L0 bodies/Jets are not supported).
 
     ``coarse_boundary`` is ``periodic`` (default) or ``slot_reservoir``:
     a bottom on-site slot and top fixed-density reservoir from ``cfg``.
@@ -145,68 +108,55 @@ class FixedPatchStepper:
     actual channel closure footprint. Channel remapping is not supported.
     Periodic mode does not apply the wall/slot boundary fields in ``cfg``.
     Outer walls remain coarse; fine halo donors must be ordinary fluid.
-    ``fine_objects`` accepts fixed circles in coarse physical coordinates;
-    velocities are in coarse lattice units (dx=dt=1). Independent local copies
-    are projected at fine cell centers. Their complete stencil must be active
-    and disjoint from the actual two-hop transfer footprint.
-    These use the edge/cell-center frame (coarse centers I+.5), whereas ordinary Simulation objects use the integer-node frame.
 
-    ``initialize(coarse_g, fine_g)`` accepts physical Q-major (9,ny,nx) arrays
-    already in postcollision phase. It does not collide or build channel flags.
-    Every ``step()`` publishes only after both levels complete on one stream.
-    On a device/launch failure the instance becomes unusable: close and recreate
-    it, rather than pretending the partially advanced fine buffer rolled back.
+    Bodies are fixed circles in root (L0) physical coordinates; velocities are
+    in root lattice units (dx=dt=1). Independent local copies are projected at
+    fine cell centers; their complete stencil must be active and disjoint from
+    the actual two-hop transfer footprint. These use the edge/cell-center frame
+    (coarse centers I+.5), whereas ordinary Simulation objects use the
+    integer-node frame. Jets (body.jets.Jet) use the same frame and drive cut
+    links selected at their true hits; ``set_jet_amplitude(index, amplitude,
+    level=l)`` re-uploads the per-link velocity column only.
+
+    ``initialize(*level_g)`` accepts one physical Q-major (9, ny, nx) array per
+    level, already in postcollision phase. It does not collide or build channel
+    flags. Every ``step()`` publishes only after all levels complete on one
+    stream. On a device/launch failure the instance becomes unusable: close and
+    recreate it, rather than pretending a partially advanced buffer rolled back.
+
+    A ``level_blocks`` entry (by, bx) stores that level in blocks.cu storage:
+    the ENTIRE level shape, including the four-cell patch ghost band, is
+    partitioned by a non-periodic BlockLayout2D with one-cell same-level halos.
+    Patch kinds stay per cell (OUTER invalid, INNER stream only, ACTIVE
+    collide); halos are gathered before each hop. Public arrays keep the dense
+    shapes; only the allocation differs. A blocked level requires blocked
+    refined levels below it; several L1 rectangles and depth >= 3 require all
+    levels blocked. Blocked bodies are stationary circles, optionally
+    surface-actuated: prepare_fine_boundary decides legality on the dense grid,
+    then cut links are staged receiver-local per hop: halo -> BFL -> step, same
+    buffer. A blocked parent gathers halos before receiver-local coalescence
+    staging and pull/collision; covered cells are poisoned on every step.
 
-    ``fine_block=(by, bx)`` (opt-in) stores the fine level in
-    blocks.cu storage: the ENTIRE fine_shape, including the four-cell patch
-    ghost band, is partitioned by a non-periodic BlockLayout2D with one-cell
-    same-level halos. Patch kinds stay per cell (OUTER invalid, INNER stream
-    only, ACTIVE collide); halos are gathered before each fine hop. Public
-    arrays keep the dense (9, ny, nx) fine shape; only the allocation differs.
-    Blocked fine_objects are stationary circles, optionally surface-actuated:
-    prepare_fine_boundary decides legality on the dense fine grid, then cut
-    links are staged receiver-local per hop: halo -> BFL -> step, same buffer.
-    ``base_block=(by, bx)`` also blocks the parent; it requires ``fine_block``.
-    Parent halos precede receiver-local coalescence staging and pull/collision;
-    covered cells are explicitly poisoned on every step. Public shapes stay dense.
     ``observe_raw_exchange=True`` records blocked physical cut-link exchange
     without changing populations. read_raw_exchange reports the last complete
     base interval or last substep in base-lattice units per unit depth. This
     is boundary momentum reaction, not a validated nozzle/stress load. Dense
-    body layouts are not supported by this new diagnostic in this candidate.
+    body levels are not supported by this diagnostic.
     ``observe_window_exchange=True`` (requires observe_raw_exchange) adds a second
     per-link FP64 ledger accumulated by the same kernel between
     start_exchange_window() and read_exchange_window(); disabled by default.
-    ``jets`` (body.jets.Jet) use the same edge frame as ``fine_objects`` and
-    drive fine cut links selected at their true hits; ``set_jet_amplitude``
-    re-uploads the per-link velocity column only.
 
-    Several patches: pass ``bounds`` as a sequence of (x0, y0, x1, y1)
-    rectangles (FixedPatchSet2D, dependency-validated union). This requires
-    fine_block and base_block; fine_objects/jets are projected once onto the
-    level-wide fine grid (each circle inside the union, body ids = object
-    positions, jet and writer checks level-wide), and
-    uses one level-wide fine grid (2*ny, 2*nx): public fine arrays have that
-    shape, NaN outside the patches' ACTIVE cells. The step sequence is the
-    blocked one above, with unique union transfers in one launch each.
-
-    Three-level separated unions: ``child_rectangles_in_parent=[...]`` is
-    mutually exclusive with scalar ``child`` and accepts either parent form.
-    Coordinates index the allocated L1 array, including ghost bands and holes:
-    root edge = patch.fine_origin + L1 index / 2. A parent set has origin zero;
-    a scalar parent retains its shifted window origin. The child set's public
-    extent is twice the allocated L1 shape, even though storage is sparse.
-    Each pair requires gap >= 4 in its own parent-cell units. All regions share
-    one buffer pair per level and the fixed 1:2:4 schedule; L2-only bodies/Jets
-    below apply unchanged, with object IDs assigned over the whole level.
-
-    Three-level single chain: ``child`` bounds use L1 window cells; all three
-    levels must be blocked. ``child_objects`` and ``child_jets`` use the L0
-    edge frame, with L2 dx=dt=.25 and unchanged lattice velocity. L1 bodies
-    and Jets remain unsupported in a chain. Every whole circle and its BFL
-    stencil must fit strictly away from the L2 transfer footprint. L2 runs
-    halo -> BFL -> step four times per base step. Runtime child Jet changes
-    require ``set_jet_amplitude(index, amplitude, level=2)``.
+    Nested levels: a child set's coordinates index the allocated parent array,
+    including ghost bands and holes: root edge = parent fine_origin + index / 2
+    (zero origin for a parent set; a scalar parent keeps its shifted window
+    origin). A scalar child requires a scalar parent. Rectangle unions impose no
+    fixed gap rule: adjacent, overlapping and concave unions are accepted when
+    their actual transfer dependencies close (FixedPatchSet2D /
+    nest_patch_set). All regions share one buffer pair per level and the fixed
+    schedule of 2**l hops per base step at level l. Bodies/Jets are supported only on the
+    finest level of a nested hierarchy (L2 dx=dt=.25 in root units, unchanged
+    lattice velocity); every whole circle and its BFL stencil must fit strictly
+    away from that level's transfer footprint.
 
     ``explosion="projected_linear"`` selects experimental transverse linear
     reconstruction on each adjacent pair. Default "constant" is unchanged.
@@ -214,43 +164,21 @@ class FixedPatchStepper:
     bodies/Jets or LES; this backend supplies no forcing. Geometry is generic,
     but union/multilevel GPU and matched-physics qualification remain pending.
 
-    Level lists (any depth): ``refinements[l]`` gives level l+1 in level-l
-    integer cells (scalar window or rectangle list, see lbm.hierarchy);
-    ``level_blocks``/``level_objects``/``level_jets`` hold one entry per level,
-    L0 included. They are mutually exclusive with the legacy keywords above,
-    which are normalised to the same lists. One recursive hop advances every
-    level: a child explodes from its parent's current hop source, takes two
-    hops, then the parent gathers halos, stages restriction, applies BFL and
-    steps. Depth >= 3 must be fully blocked with bodies/Jets on the finest level.
+    One recursive hop advances every level: a child explodes from its parent's
+    current hop source, takes two hops, then the parent gathers halos, stages
+    restriction, applies BFL and steps.
     """
-    def __init__(self, cfg, bounds=None, *, context, coarse_boundary="periodic", fine_objects=(),
-                 fine_block=None, base_block=None, jets=(), child=None, child_block=None,
-                 child_objects=(), child_jets=(), child_rectangles_in_parent=None,
-                 refinements=None, level_blocks=None, level_objects=None, level_jets=None,
+    def __init__(self, cfg, *, context, refinements, coarse_boundary="periodic",
+                 level_blocks=None, level_objects=None, level_jets=None,
                  observe_raw_exchange=False, observe_window_exchange=False, explosion="constant"):
         if HALO != 4:
             raise RuntimeError("refinement.cu requires a four-cell fine halo")
         if coarse_boundary not in ("periodic", "slot_reservoir", "channel"):
             raise ValueError("coarse_boundary must be periodic, slot_reservoir or channel")
-        if refinements is None:
-            if bounds is None:
-                raise ValueError("bounds or refinements is required")
-            if level_blocks is not None or level_objects is not None or level_jets is not None:
-                raise ValueError("level_blocks/level_objects/level_jets require refinements")
-            refinements, level_blocks, level_objects, level_jets = _legacy_levels(
-                bounds, fine_block=fine_block, base_block=base_block, child=child,
-                child_block=child_block, child_rectangles_in_parent=child_rectangles_in_parent,
-                fine_objects=fine_objects, jets=jets, child_objects=child_objects,
-                child_jets=child_jets)
-        else:
-            if (bounds is not None or child is not None or child_rectangles_in_parent is not None
-                    or fine_block is not None or base_block is not None or child_block is not None
-                    or tuple(fine_objects) or tuple(jets) or tuple(child_objects) or tuple(child_jets)):
-                raise ValueError("refinements and the legacy patch keywords are mutually exclusive")
-            depth = len(refinements) + 1
-            level_blocks = [None] * depth if level_blocks is None else list(level_blocks)
-            level_objects = [()] * depth if level_objects is None else list(level_objects)
-            level_jets = [()] * depth if level_jets is None else list(level_jets)
+        depth = len(refinements) + 1
+        level_blocks = [None] * depth if level_blocks is None else list(level_blocks)
+        level_objects = [()] * depth if level_objects is None else list(level_objects)
+        level_jets = [()] * depth if level_jets is None else list(level_jets)
         level_objects = [tuple(o) for o in level_objects]
         level_jets = [tuple(j) for j in level_jets]
         level_blocks = [None if b is None else tuple(b) for b in level_blocks]
@@ -540,13 +468,13 @@ class FixedPatchStepper:
         if self._ddf_shifting and any(layout is None for layout in self._layouts):
             raise ValueError("shifted populations require all-blocked levels")
 
-    def initialize(self, *level_g, coarse_g=None, fine_g=None, child_g=None):
+    def initialize(self, *level_g):
         """Upload physical postcollision G, encoding before any FP32 rounding.
 
         Shifted input should be physical FP64 to retain small perturbations.
         Public initialization resets the step count; non-leaves are discarded.
         """
-        given = _initial_levels(level_g, coarse_g, fine_g, child_g)
+        given = tuple(level_g)
         with self._lock, self.ctx.activate():
             self._require("new", "ready")
             self._check_storage()
@@ -670,10 +598,9 @@ class FixedPatchStepper:
                 old, new, source, base_count=count, level_steps=(count, 2*count, 4*count),
                 phase="postcollision_g", **options)
             candidate = type(self)(
-                cfg, pairs[0].bounds, context=self.ctx, base_block=base_block,
-                fine_block=fine_block, child_block=child_block,
-                child_rectangles_in_parent=new.child.bounds,
-                child_objects=child_objects, child_jets=jets,
+                cfg, context=self.ctx, refinements=[pairs[0].bounds, new.child.bounds],
+                level_blocks=[base_block, fine_block, child_block],
+                level_objects=[(), (), child_objects], level_jets=[(), (), jets],
                 observe_raw_exchange=self._observe_raw_exchange,
                 observe_window_exchange=self._observe_window, explosion=self._explosion)
             try:

src/CelerisLab/lbm/refinement_tables.py

@@ -8,7 +8,7 @@ from dataclasses import dataclass, replace
 import numpy as np
 
 from .blocks import blocked_link_tables
-from ..body.jets import jet_link_shapes, surface_link_velocity
+from ..body.jets import _surface_links
 from .descriptors import D2Q9_EX, D2Q9_EY
 from .refinement import ACTIVE, OUTER_GHOST
 
@@ -142,11 +142,13 @@ def _prepare_blocked_boundary(boundary, layout, cfg, jets, *, _shifted_blocked=F
     tables.update(body_id=np.asarray(body_id, np.int32), rx=np.asarray(rx, np.float32),
                   ry=np.asarray(ry, np.float32), aperture=np.zeros(len(dirs), bool))
     actuated = bool(jets) or any(o.surface_actuation is not None for o in boundary.objects)
+    jet_cache = None
     if actuated:
         cfg = replace(cfg)
         cfg.validate()
-        tables["surface_velocity"], tables["aperture"] = surface_link_velocity(
+        tables["surface_velocity"], tables["aperture"], shape, jet_id = _surface_links(
             boundary.objects, cfg, boundary.flags, fluid_idx, dirs, body_id, rx, ry,
             jets=jets, hits=boundary.curved_hits, _shifted_blocked=_shifted_blocked)
-    return _BlockedBoundary(boundary, tables, jets, actuated,
-                            jet_link_shapes(jets, boundary.curved_hits) if jets else None)
+        if jets:
+            jet_cache = (shape, jet_id)
+    return _BlockedBoundary(boundary, tables, jets, actuated, jet_cache)

tests/unit/test_channel_root.py

@@ -50,7 +50,7 @@ def test_masks_and_minimal_footprint():
 def test_actual_closure_read_conflicts():
     pair, layout, targets = transfer((6, 6, 18, 14))
     validate_channel_transfers(pair, layout, targets)
-    for target in (layout.slot(layout.owner[5, -1]-1, 2),
+    for target in (layout.slot(int(layout.owner[5, -1]) - 1, 2),  # integer under NumPy 1 and 2
                    layout.slot(layout.owner[1, 4], 4),
                    layout.slot(layout.owner[-2, 4], 3)):
         with pytest.raises(ValueError, match="immutable"):
@@ -80,8 +80,8 @@ def test_evolved_ghost_snapshot_and_physical_download():
     host.cuda.memcpy_dtoh.side_effect = lambda a, ptr: np.copyto(a, storage[id(ptr)])
     context = Mock(activate=nullcontext, sm_arch="sm_70")
     cfg = LBMConfig(nx=24, ny=20, viscosity=.1, velocity=.025)
-    backend = host.FixedPatchStepper(cfg, (6, 6, 18, 14), context=context,
-                                    coarse_boundary="channel", base_block=(4, 6), fine_block=(4, 4))
+    backend = host.FixedPatchStepper(cfg, context=context, coarse_boundary="channel",
+                                    refinements=[(6, 6, 18, 14)], level_blocks=[(4, 6), (4, 4)])
     try:
         weights = np.array([4/9]+[1/9]*4+[1/36]*4)[:, None, None]
         arrays = [np.broadcast_to(weights, level.shape).copy() for level in backend._levels]

tests/unit/test_raw_exchange.py

@@ -157,8 +157,9 @@ class RawExchange(unittest.TestCase):
         host = host_module()
         ctx = Mock()
         with self.assertRaisesRegex(ValueError, 'blocked body'):
-            host.FixedPatchStepper(LBMConfig(nx=32, ny=32, viscosity=.1), (4, 4, 28, 28),
-                                   context=ctx, fine_objects=[body(radius=2.15)], observe_raw_exchange=True)
+            host.FixedPatchStepper(LBMConfig(nx=32, ny=32, viscosity=.1), context=ctx,
+                                   refinements=[(4, 4, 28, 28)],
+                                   level_objects=[(), (body(radius=2.15),)], observe_raw_exchange=True)
         ctx.activate.assert_not_called()
 
     def test_all_depth_weights(self):

tests/unit/test_refined_dfg.py

@@ -141,16 +141,47 @@ def test_axis_specific_sampling_phase():
     np.testing.assert_allclose(fine_y - ((k + 43) - 0.5) * 0.00125, 0, atol=1e-15)
 
 
+def frozen_manifest(observation_mode):
+    """Frozen MRT manifest JSON as recorded, without hashing the working tree."""
+    name = "source_manifest_window.json" if observation_mode == "window" else "source_manifest_mrt.json"
+    return json.loads((r.HERE / "data/refined_dfg" / name).read_text())
+
+
+def selected_manifest(collision, observation_mode):
+    """verify_source's manifest selection with its working-tree hash comparison neutralised.
+
+    Source identity is owned by test_source_pin; this exercises only which frozen manifest
+    verify_source selects and returns for (collision, observation_mode).
+    """
+    from unittest.mock import patch
+
+    class Digest(str):
+        def __ne__(self, other):
+            return False
+
+    class Hash:
+        def __init__(self, data=b""):
+            pass
+
+        def hexdigest(self):
+            return Digest()
+
+    with patch.object(r.hashlib, "sha256", Hash):
+        return r.verify_source(r.DEFAULT_SOURCE, collision, observation_mode)
+
+
 def test_full_requires_completed_pilot():
     with unittest.TestCase().assertRaisesRegex(ValueError, "pilot-results"):
-        r.verify_pilot(None, r.verify_source(r.DEFAULT_SOURCE, "MRT", "window"))
+        r.verify_pilot(None, frozen_manifest("window"))
 
 
 def pilot_fixture(path, observation_mode="window", jet_scenario="none", case_selection="both", uniform_diameter=80, placement="wide"):
     """Synthetic contract fixture only; never a physical result or run receipt."""
+    # Receipt-logic fixture: the frozen manifest verify_source returns for a matching tree.
+    # Source identity itself is checked only by test_source_pin.
     manifest = (r.verify_source(r.DEFAULT_SOURCE, "MRT", "window", jet_scenario)
-                if observation_mode == "window" else
-                json.loads((r.HERE / "data/refined_dfg/source_manifest_mrt.json").read_text()))
+                if observation_mode == "window" and jet_scenario != "none" else
+                frozen_manifest(observation_mode))
     selection = dict(case_selection=case_selection, uniform_diameter=uniform_diameter, placement=placement)
     (path / "plan.json").write_text(
         json.dumps(
@@ -348,7 +379,7 @@ def test_record_actual_checkout_separately():
     actual = checkout_provenance(r.DEFAULT_SOURCE)
     assert len(actual["checkout_revision"]) == 40
     assert isinstance(actual["checkout_dirty"], bool)
-    assert r.verify_source(r.DEFAULT_SOURCE, "MRT", "window")["production_origin_commit"].startswith("d930")
+    assert selected_manifest("MRT", "window")["production_origin_commit"].startswith("d930")
 
 
 def test_window_plan_preserves_physics():
@@ -358,7 +389,7 @@ def test_window_plan_preserves_physics():
         assert baseline.pop("observation_mode") == "last_base_step"
         assert window.pop("observation_mode") == "window"
         assert baseline == window
-        assert r.verify_source(r.DEFAULT_SOURCE, collision, "window")["observation_mode"] == "window"
+        assert selected_manifest(collision, "window")["observation_mode"] == "window"
     with unittest.TestCase().assertRaises(ValueError):
         r.verify_source(r.DEFAULT_SOURCE, "MRT", "unknown")
 

tests/unit/test_refinement_mrt.py

@@ -37,8 +37,13 @@ class RefinementMRTHost(unittest.TestCase):
             self.assertIn("STORE_PRECISION != 0", source)
             self.assertIn('#if COLLISION_MODEL == 2\n#include "operators/collision_mrt.cuh"\n#endif', source)
         self.assertIn("USE_DDF_SHIFTING ||", refinement)  # dense/mixed shifted stays rejected
+        # One shared unforced MRT body; each blocked/patch path calls it exactly once.
+        mrt = (KERNELS / "operators/collision_mrt.cuh").read_text()
+        self.assertEqual(mrt.count("void collide_mrt_unforced("), 1)
         for source in (blocks, channel, refinement):
-            self.assertEqual(source.count("collide_mrt_no_force("), 1)
+            self.assertEqual(source.count("collide_mrt_unforced(f);"), 1)
+            self.assertNotIn("collide_mrt_no_force(", source)
+            self.assertNotIn("compute_rho_u(f, rho, ux, uy);\n            collide_mrt", source)
 
 
 if __name__ == "__main__": unittest.main()

tests/unit/test_refinement_three_level_multipatch.py

@@ -173,8 +173,10 @@ def bodies_and_jets(speed=.002):
     return bodies,jets
 
 
-KW=dict(base_block=(4,4),fine_block=(4,4),child_block=(4,4),
-        child_rectangles_in_parent=CHILDREN)
+def levels(parents=PARENTS,children=CHILDREN,blocks=((4,4),)*3,objects=((),(),()),jets=((),(),())):
+    """Level-list constructor keywords for the L0 set, L1 set and L2 set used here."""
+    return dict(refinements=[parents,children],level_blocks=list(blocks),
+                level_objects=list(objects),level_jets=list(jets))
 
 
 def mock_backend(*, children=CHILDREN, bodies=False, fail_compile=False, fail_upload=False):
@@ -201,9 +203,8 @@ def mock_backend(*, children=CHILDREN, bodies=False, fail_compile=False, fail_up
         module.cuda.memcpy_htod.side_effect=upload
     objects,jets=bodies_and_jets() if bodies else ((),())
     try:
-        run=module.FixedPatchStepper(CFG,PARENTS,context=context,
-            child_objects=objects,child_jets=jets,
-            **dict(KW,child_rectangles_in_parent=children))
+        run=module.FixedPatchStepper(CFG,context=context,
+            **levels(children=children,objects=((),(),objects),jets=((),(),jets)))
     except RuntimeError:
         for allocation in allocations:
             allocation.free.assert_called_once_with()
@@ -214,28 +215,29 @@ def mock_backend(*, children=CHILDREN, bodies=False, fail_compile=False, fail_up
 class ConstructorAndSchedule(unittest.TestCase):
     def test_invalid_inputs_fail_before_context_or_allocations(self):
         context=Mock()
-        cases=[dict(child=(8,8,16,16)),dict(child_rectangles_in_parent=[]),
-               dict(child_rectangles_in_parent=[(16,16,32)]),
-               dict(child_rectangles_in_parent=[(16.5,16,32,40)]),
-               dict(child_rectangles_in_parent=[(16,16,32,24),(16,27,32,55)]),
-               dict(child_rectangles_in_parent=[(40,16,48,40)]),
-               dict(child_rectangles_in_parent=[(8,16,32,40)]),
-               dict(child_block=None),dict(fine_block=None),dict(base_block=None),
-               dict(child_block=(5,4)),dict(fine_block=(5,4)),
-               dict(child_block=(4,)),dict(child_rectangles_in_parent=(16,16,32,40))]
+        b=(4,4)
+        cases=[dict(children=(8,8,16,16)),dict(children=[]),
+               dict(children=[(16,16,32)]),
+               dict(children=[(16.5,16,32,40)]),
+               dict(children=[(16,16,32,24),(16,27,32,55)]),
+               dict(children=[(40,16,48,40)]),
+               dict(children=[(8,16,32,40)]),
+               dict(blocks=(b,b,None)),dict(blocks=(b,None,b)),dict(blocks=(None,b,b)),
+               dict(blocks=(b,b,(5,4))),dict(blocks=(b,(5,4),b)),
+               dict(blocks=(b,b,(4,))),dict(children=(16,16,32,40))]
         for changes in cases:
             with self.subTest(changes=changes),self.assertRaises((ValueError,TypeError)):
-                host.FixedPatchStepper(CFG,PARENTS,context=context,**dict(KW,**changes))
+                host.FixedPatchStepper(CFG,context=context,**levels(**changes))
         with self.assertRaisesRegex(ValueError,'margin'):
-            host.FixedPatchStepper(CFG,[(1,4,20,28),(23,4,44,28)],context=context,**KW)
+            host.FixedPatchStepper(CFG,context=context,**levels(parents=[(1,4,20,28),(23,4,44,28)]))
         objects,jets=bodies_and_jets()
-        with self.assertRaisesRegex(ValueError,'only on L2'):
-            host.FixedPatchStepper(CFG,PARENTS,context=context,fine_objects=objects,**KW)
+        with self.assertRaisesRegex(ValueError,'only on the finest level'):
+            host.FixedPatchStepper(CFG,context=context,**levels(objects=((),objects,())))
         from CelerisLab.body.jets import Jet,Tube,Parallel
         spanning=Jet(Tube((10.5,14.),0.,25.,.3),Parallel(0.),amplitude=0.)
         with self.assertRaisesRegex(ValueError,'one jet'):
-            host.FixedPatchStepper(CFG,PARENTS,context=context,child_objects=objects,
-                                  child_jets=[spanning],**KW)
+            host.FixedPatchStepper(CFG,context=context,
+                                  **levels(objects=((),(),objects),jets=((),(),[spanning])))
         context.activate.assert_not_called()
         host.cuda.mem_alloc.assert_not_called()
 
@@ -313,21 +315,23 @@ class ConstructorAndSchedule(unittest.TestCase):
 
 
 
-class InitialLevels(unittest.TestCase):
-    """initialize() entry adapter: positional per-level arrays or the legacy names, never both."""
+class RemovedLegacyAPI(unittest.TestCase):
+    """The pre-level-list constructor/initialize forms are gone and fail loudly."""
 
-    def test_forms(self):
-        a, b, c = object(), object(), object()
-        f = host._initial_levels
-        self.assertEqual(f((a, b), None, None, None), (a, b))
-        self.assertEqual(f((a, b, c), None, None, None), (a, b, c))
-        self.assertEqual(f((a, b), None, None, c), (a, b, c))      # old initialize(c, f, child_g=g)
-        self.assertEqual(f((), a, b, None), (a, b))
-        self.assertEqual(f((), a, b, c), (a, b, c))
-        for args in (((a,), None, None, c), ((a, b, c), None, None, c), ((a,), a, b, None),
-                     ((), a, None, None), ((), None, b, c)):
-            with self.subTest(args=args), self.assertRaises(TypeError):
-                f(*args)
+    def test_removed_constructor_forms_raise_type_error(self):
+        import inspect
+        context = Mock()
+        with self.assertRaises(TypeError):  # positional bounds
+            host.FixedPatchStepper(CFG, PARENTS, context=context)
+        removed = dict(bounds=PARENTS, fine_block=(4, 4), base_block=(4, 4), fine_objects=(),
+                       jets=(), child=(8, 8, 16, 16), child_block=(4, 4), child_objects=(),
+                       child_jets=(), child_rectangles_in_parent=CHILDREN)
+        for name, value in removed.items():
+            with self.subTest(keyword=name), self.assertRaises(TypeError):
+                host.FixedPatchStepper(CFG, context=context, **levels(), **{name: value})
+        context.activate.assert_not_called()
+        self.assertEqual(list(inspect.signature(host.FixedPatchStepper.initialize).parameters),
+                         ["self", "level_g"])  # no coarse_g/fine_g/child_g
 
 
 if __name__=='__main__':

tests/unit/test_shifted_jets.py

@@ -54,14 +54,13 @@ class ShiftedJets(unittest.TestCase):
                 (Jet(Tube((10.,14.),0.,26.,.3),Parallel(0.)),))]
         for objects,jets in cases:
             with self.subTest(objects=len(objects),jets=len(jets)),self.assertRaises(ValueError):
-                module.FixedPatchStepper(CFG,backend.PARENTS,context=None,
-                    base_block=(4,4),fine_block=(4,4),child_block=(4,4),
-                    child_rectangles_in_parent=A,child_objects=objects,child_jets=jets)
+                module.FixedPatchStepper(CFG,context=None,refinements=[backend.PARENTS,A],
+                    level_blocks=[(4,4)]*3,level_objects=[(),(),objects],level_jets=[(),(),jets])
         for blocks in ((None,None,None),((4,4),None,(4,4))):
             with self.assertRaises(ValueError):
-                module.FixedPatchStepper(CFG,backend.PARENTS,context=None,
-                    base_block=blocks[0],fine_block=blocks[1],child_block=blocks[2],
-                    child_rectangles_in_parent=A,child_objects=(body(),),child_jets=(jet(),))
+                module.FixedPatchStepper(CFG,context=None,refinements=[backend.PARENTS,A],
+                    level_blocks=list(blocks),level_objects=[(),(),(body(),)],
+                    level_jets=[(),(),(jet(),)])
         module.cuda.mem_alloc.assert_not_called()
         module.compiler.compile_kernel.assert_not_called()
 

tests/unit/test_shifted_storage.py

@@ -78,13 +78,15 @@ class ShiftedStorage(unittest.TestCase):
 
     def test_shifted_density_and_tag_validation(self):
         old,new = topology(A),topology(B)
-        a = tuple(np.where(m[None], np.float32(-.001), np.nan).repeat(9,axis=0) for m in old.leaf_masks)
+        a = tuple(np.where(m[None], np.float32(-.001), np.float32(np.nan)).repeat(9,axis=0)
+                  for m in old.leaf_masks)  # FP32 under NumPy 1 and 2 promotion rules
         remap(old,new,a)
         with self.assertRaisesRegex(ValueError,'representation'): remap(old,new,a,False)
         with self.assertRaisesRegex(ValueError,'FP32'): remap(old,new,tuple(x.astype(np.float64) for x in a))
         a[0][:,old.leaf_masks[0]] = -1
         with self.assertRaisesRegex(ValueError,'positive density'): remap(old,new,a)
-        rest = tuple(np.where(m[None],np.float32(0),np.nan).repeat(9,axis=0) for m in old.leaf_masks)
+        rest = tuple(np.where(m[None],np.float32(0),np.float32(np.nan)).repeat(9,axis=0)
+                     for m in old.leaf_masks)
         remap(old,new,rest)
         with self.assertRaisesRegex(ValueError,'positive density'):
             remap_synchronized(old,new,rest,base_count=7,level_steps=(7,14,28),phase='postcollision_g')
@@ -129,9 +131,10 @@ class ShiftedStorage(unittest.TestCase):
     def test_dense_or_mixed_shifted_rejected_before_compilation(self):
         module=backend.host_module()
         cfg=replace(backend.CFG,ddf_shifting=True)
-        for kwargs in ({},dict(base_block=(4,4)),dict(fine_block=(4,4))):
-            with self.assertRaisesRegex(ValueError,'all-blocked|base_block requires fine_block'):
-                module.FixedPatchStepper(cfg,(4,4,20,28),context=None,**kwargs)
+        for blocks in ([None,None],[(4,4),None],[None,(4,4)]):
+            with self.assertRaisesRegex(ValueError,'all-blocked|blocked refined levels below'):
+                module.FixedPatchStepper(cfg,context=None,refinements=[(4,4,20,28)],
+                                         level_blocks=blocks)
         module.compiler.compile_kernel.assert_not_called()
 
     def test_uniform_block_codec_and_raw_snapshot(self):

tests/validation/multigrid/test_block_stepper.py

@@ -192,6 +192,7 @@ class CpuContracts(unittest.TestCase):
         backend._lock = RLock()
         backend._status = "ready"
         backend._step_count = 0
+        backend._ddf_shifting = False  # unshifted storage, as for the default config
         backend._stream = Mock()
         backend._module = Mock()
         backend._copy = backend._step = Mock()

tests/validation/multigrid/test_channel_root_gpu.py

@@ -106,9 +106,10 @@ class ChannelRootGPU(unittest.TestCase):
                     cfg = LBMConfig(nx=48, ny=32, viscosity=.1, velocity=.015, ddf_shifting=shifted)
                     reference = None
                     for block in ((32,48), (8,8), (4,1)):
-                        with FixedPatchStepper(cfg, (8,6,40,26), context=context,
-                                coarse_boundary="channel", base_block=block, fine_block=(8,8),
-                                fine_objects=(body,) if bodies else (), jets=(jet,) if bodies else ()) as backend:
+                        with FixedPatchStepper(cfg, context=context, coarse_boundary="channel",
+                                refinements=[(8,6,40,26)], level_blocks=[block, (8,8)],
+                                level_objects=[(), (body,) if bodies else ()],
+                                level_jets=[(), (jet,) if bodies else ()]) as backend:
                             arrays = [state(*level.shape[1:]) for level in backend._levels]
                             backend.initialize(*arrays)
                             backend.step(4)

tests/validation/multigrid/test_exchange_window.py

@@ -25,8 +25,8 @@ EPS = np.finfo(np.float64).eps
 
 
 def build(m, window=True, raw=True):
-    return FixedPatchStepper(config("periodic"), BOUNDS, context=m["context"], base_block=(3, 4),
-                             fine_block=(16, 20), fine_objects=[circle()],
+    return FixedPatchStepper(config("periodic"), context=m["context"], refinements=[BOUNDS],
+                             level_blocks=[(3, 4), (16, 20)], level_objects=[(), (circle(),)],
                              observe_raw_exchange=raw, observe_window_exchange=window)
 
 
@@ -109,10 +109,11 @@ class ExchangeWindowGPU(unittest.TestCase):
         from test_raw_exchange_gpu import BOUNDS as RB, CFG, circle as rc, jet, state
         from CelerisLab.cuda.context import CudaContext
         with CudaContext(0) as ctx:
-            kw = dict(context=ctx, fine_block=(16, 20), fine_objects=[rc()], jets=[jet()],
+            kw = dict(context=ctx, refinements=[RB], level_blocks=[None, (16, 20)],
+                      level_objects=[(), (rc(),)], level_jets=[(), (jet(),)],
                       observe_raw_exchange=True)
-            with FixedPatchStepper(CFG, RB, observe_window_exchange=True, **kw) as windowed, \
-                 FixedPatchStepper(CFG, RB, **kw) as plain:
+            with FixedPatchStepper(CFG, observe_window_exchange=True, **kw) as windowed, \
+                 FixedPatchStepper(CFG, **kw) as plain:
                 arrays = [state(level.shape) for level in windowed._levels]
                 windowed.initialize(*arrays)
                 plain.initialize(*arrays)
@@ -200,11 +201,11 @@ class ExchangeWindowShiftedMRTGPU(unittest.TestCase):
         from CelerisLab.cuda.context import CudaContext
         cfg = LBMConfig(nx=32, ny=24, viscosity=.1, collision="MRT", ddf_shifting=True)
         with CudaContext(0) as ctx:
-            kw = dict(context=ctx, base_block=(12, 8), fine_block=(16, 20), fine_objects=[rc()],
-                      observe_raw_exchange=True)
-            with FixedPatchStepper(cfg, RB, observe_window_exchange=True, **kw) as windowed, \
-                 FixedPatchStepper(cfg, RB, observe_window_exchange=True, **kw) as split, \
-                 FixedPatchStepper(cfg, RB, **kw) as plain:
+            kw = dict(context=ctx, refinements=[RB], level_blocks=[(12, 8), (16, 20)],
+                      level_objects=[(), (rc(),)], observe_raw_exchange=True)
+            with FixedPatchStepper(cfg, observe_window_exchange=True, **kw) as windowed, \
+                 FixedPatchStepper(cfg, observe_window_exchange=True, **kw) as split, \
+                 FixedPatchStepper(cfg, **kw) as plain:
                 arrays = [state(level.shape) for level in windowed._levels]
                 for run in (windowed, split, plain):
                     run.initialize(*arrays)

tests/validation/multigrid/test_fine_surface_gpu.py

@@ -140,7 +140,8 @@ def run_patch(speed, *, audit=True):
         build = (patch.object(compiler, "compile_kernel", audit_compiler(compiler.compile_kernel))
                  if audit else nullcontext())
         with build:
-            backend = implementation.FixedPatchStepper(cfg, BOUNDS, context=context, fine_objects=[source])
+            backend = implementation.FixedPatchStepper(cfg, context=context, refinements=[BOUNDS],
+                                             level_objects=[(), (source,)])
         with backend, context.activate():
             c, f = backend._levels
             cl = backend._fine_curved
@@ -281,7 +282,8 @@ def test_fine_surface_four_hops(speed):
 @pytest.mark.parametrize("missing", ["surface_velocity_gpu", "link_exchange_gpu"])
 def test_missing_surface_device_buffer_rejects_before_launch(missing):
     backend = implementation.FixedPatchStepper.__new__(implementation.FixedPatchStepper)
-    backend.fine_boundary = SimpleNamespace(objects=[object_spec(.002)])
+    backend._boundary_hosts = [None, SimpleNamespace(objects=[object_spec(.002)])]
+    backend._level_jets = [(), ()]
     backend._fine_curved = SimpleNamespace(fluid_idx_gpu=object(),
                                           surface_velocity_gpu=object(), link_exchange_gpu=object())
     setattr(backend._fine_curved, missing, None)
@@ -325,6 +327,7 @@ def test_cross_interface_donor_rejects_before_cuda():
     context.activate.side_effect = AssertionError("must reject before CUDA activation")
     with patch.object(cuda, "mem_alloc") as allocate:
         with pytest.raises(ValueError, match="donor crosses"):
-            implementation.FixedPatchStepper(cfg, BOUNDS, context=context, fine_objects=[source])
+            implementation.FixedPatchStepper(cfg, context=context, refinements=[BOUNDS],
+                                             level_objects=[(), (source,)])
         context.activate.assert_not_called()
         allocate.assert_not_called()

tests/validation/multigrid/test_multiple_pinned_remap_gpu.py

@@ -48,9 +48,8 @@ def make(context):
         for (x, y), amplitude in zip(centers, (.003, -.002))
     )
     run = FixedPatchStepper(
-        CFG, PARENTS, context=context, base_block=(4, 4), fine_block=(4, 4),
-        child_block=(4, 4), child_rectangles_in_parent=START,
-        child_objects=objects, child_jets=jets,
+        CFG, context=context, refinements=[PARENTS, START], level_blocks=[(4, 4)] * 3,
+        level_objects=[(), (), objects], level_jets=[(), (), jets],
     )
     return run, objects
 

tests/validation/multigrid/test_pinned_body_remap_gpu.py

@@ -25,9 +25,8 @@ B = ((16,16,32,40), (60,16,76,40))
 def make(ctx):
     body = SimObject(71, geometry=CircleGeometry(12.,14.,.8),center=(12.,14.),radius=.8)
     jet = Jet(Tube((10.5,14.),0.,3.,.3),Parallel(0.),'parabolic',.003)
-    run = FixedPatchStepper(CFG,PARENTS,context=ctx,base_block=(4,4),fine_block=(4,4),
-                           child_block=(4,4),child_rectangles_in_parent=A,
-                           child_objects=(body,),child_jets=(jet,))
+    run = FixedPatchStepper(CFG,context=ctx,refinements=[PARENTS,A],level_blocks=[(4,4)]*3,
+                           level_objects=[(),(),(body,)],level_jets=[(),(),(jet,)])
     return run,(body,)
 
 

tests/validation/multigrid/test_raw_exchange_gpu.py

@@ -90,14 +90,18 @@ def census(run, index, buffer):
     return totals(dense, leaf), external, independent
 
 
+
+def fine(block):
+    """Two-level circle+jet construction on BOUNDS; block None keeps the dense fine level."""
+    return dict(refinements=[BOUNDS], level_blocks=[None, block],
+                level_objects=[(), (circle(),)], level_jets=[(), (jet(),)])
+
 class RawExchangeGPU(unittest.TestCase):
     def test_row_ledger_interval_jet_switch_and_no_population_effect(self):
         with CudaContext(0) as ctx:
             for block in ((32, 40), (16, 20), (8, 10)):
-                with FixedPatchStepper(CFG, BOUNDS, context=ctx, fine_block=block,
-                        fine_objects=[circle()], jets=[jet()], observe_raw_exchange=True) as measured, \
-                     FixedPatchStepper(CFG, BOUNDS, context=ctx, fine_block=block,
-                        fine_objects=[circle()], jets=[jet()]) as plain:
+                with FixedPatchStepper(CFG, context=ctx, **fine(block), observe_raw_exchange=True) as measured, \
+                     FixedPatchStepper(CFG, context=ctx, **fine(block)) as plain:
                     arrays = [state(l.shape) for l in measured._levels]
                     measured.initialize(*arrays)
                     plain.initialize(*arrays)
@@ -146,9 +150,8 @@ class RawExchangeGPU(unittest.TestCase):
         """Same fine resolution/initial data with dense storage: a numerical
         reference for cut-link rows, not a uniform-whole-domain convergence study."""
         with CudaContext(0) as ctx:
-            with FixedPatchStepper(CFG, BOUNDS, context=ctx, fine_objects=[circle()], jets=[jet()]) as dense, \
-                 FixedPatchStepper(CFG, BOUNDS, context=ctx, fine_block=(16, 20),
-                    fine_objects=[circle()], jets=[jet()], observe_raw_exchange=True) as blocked:
+            with FixedPatchStepper(CFG, context=ctx, **fine(None)) as dense, \
+                 FixedPatchStepper(CFG, context=ctx, **fine((16, 20)), observe_raw_exchange=True) as blocked:
                 arrays = [state(l.shape) for l in blocked._levels]
                 dense.initialize(*arrays)
                 blocked.initialize(*arrays)
@@ -229,8 +232,7 @@ class RawExchangeGPU(unittest.TestCase):
         layout = BlockLayout2D.build(48, 64, 8, 8)
         with CudaContext(0) as ctx:
             with PeriodicBlockStepper(fine_cfg, layout, context=ctx, objects=[obj]) as uniform, \
-                 FixedPatchStepper(CFG, BOUNDS, context=ctx, fine_block=(16, 20),
-                    fine_objects=[circle()], jets=[jet()], observe_raw_exchange=True) as amr:
+                 FixedPatchStepper(CFG, context=ctx, **fine((16, 20)), observe_raw_exchange=True) as amr:
                 amr.initialize(*(state(l.shape) for l in amr._levels))
                 uniform.initialize(state((9, 48, 64)))
                 b = amr._level_boundaries[1]

tests/validation/multigrid/test_refinement_blocked_base.py

@@ -83,11 +83,10 @@ def mocked_backend(mode="periodic", fail_alloc=None):
 class BlockedBaseCPU(unittest.TestCase):
     def test_reject_before_cuda(self):
         context = Mock(activate=Mock(side_effect=AssertionError("CUDA reached")))
-        for kwargs in ({"base_block": (12, 8)},
-                       {"base_block": (7, 8), "fine_block": FINE_BLOCK},
-                       {"base_block": (12,), "fine_block": FINE_BLOCK}):
-            with self.subTest(kwargs=kwargs), self.assertRaises(ValueError):
-                FixedPatchStepper(config("periodic"), BOUNDS, context=context, **kwargs)
+        for blocks in ([(12, 8), None], [(7, 8), FINE_BLOCK], [(12,), FINE_BLOCK]):
+            with self.subTest(blocks=blocks), self.assertRaises(ValueError):
+                FixedPatchStepper(config("periodic"), context=context, refinements=[BOUNDS],
+                                  level_blocks=blocks)
         context.activate.assert_not_called()
 
     def test_all_arrival_rows_donors_and_kind_masks(self):
@@ -193,9 +192,10 @@ class BlockedBaseCPU(unittest.TestCase):
 
     def test_launch_order_stream_wall_constants_and_buffer_swaps(self):
         with mocked_backend("slot_reservoir") as m:
-            backend = FixedPatchStepper(config("slot_reservoir"), BOUNDS, context=m["context"],
-                                        coarse_boundary="slot_reservoir", fine_block=FINE_BLOCK,
-                                        base_block=(3, 4), fine_objects=[circle(actuation(.002))])
+            backend = FixedPatchStepper(config("slot_reservoir"), context=m["context"],
+                                        coarse_boundary="slot_reservoir", refinements=[BOUNDS],
+                                        level_blocks=[(3, 4), FINE_BLOCK],
+                                        level_objects=[(), (circle(actuation(.002)),)])
             try:
                 backend.initialize(state(NY, NX, 1), state(*backend.patch.fine_shape, 2))
                 coarse, fine = backend._levels
@@ -236,16 +236,16 @@ class BlockedBaseCPU(unittest.TestCase):
         for fail_at in (1, 6, 10):
             with self.subTest(fail_at=fail_at), mocked_backend(fail_alloc=fail_at) as m:
                 with self.assertRaisesRegex(MemoryError, "injected allocation"):
-                    FixedPatchStepper(config("periodic"), BOUNDS, context=m["context"],
-                                      fine_block=FINE_BLOCK, base_block=(3, 4))
+                    FixedPatchStepper(config("periodic"), context=m["context"], refinements=[BOUNDS],
+                                      level_blocks=[(3, 4), FINE_BLOCK])
                 self.assertEqual(len(m["allocations"]), fail_at)
                 for allocation in m["allocations"]:
                     allocation.free.assert_called_once_with()
 
     def test_failed_parent_stage_cannot_publish_or_resume(self):
         with mocked_backend() as m:
-            backend = FixedPatchStepper(config("periodic"), BOUNDS, context=m["context"],
-                                        fine_block=FINE_BLOCK, base_block=(3, 4))
+            backend = FixedPatchStepper(config("periodic"), context=m["context"], refinements=[BOUNDS],
+                                        level_blocks=[(3, 4), FINE_BLOCK])
             backend.initialize(state(NY, NX, 1), state(*backend.patch.fine_shape, 2))
             m["functions"]["BlockCoalesce"].side_effect = RuntimeError("injected parent stage failure")
             current = backend._levels[0].current
@@ -289,9 +289,10 @@ class BlockedBaseGPU(unittest.TestCase):
                     for base_block in (None, *layouts):
                         label = f"{mode} width={width} speed={speed} base={base_block}"
                         snapshots = []
-                        with FixedPatchStepper(cfg, BOUNDS, context=context, coarse_boundary=mode,
-                                               fine_block=FINE_BLOCK, base_block=base_block,
-                                               fine_objects=() if speed is None else [circle(actuation(speed))]) as backend:
+                        with FixedPatchStepper(cfg, context=context, coarse_boundary=mode,
+                                               refinements=[BOUNDS], level_blocks=[base_block, FINE_BLOCK],
+                                               level_objects=[(), () if speed is None
+                                                              else (circle(actuation(speed)),)]) as backend:
                             backend.initialize(*arrays)
                             for step in (0, 1, 2, 8):
                                 if step == 1 and base_block is not None:

tests/validation/multigrid/test_refinement_blocked_fine.py

@@ -105,9 +105,10 @@ class BlockedFineCPU(unittest.TestCase):
         return Mock(activate=Mock(side_effect=AssertionError("CUDA reached")), sm_arch="sm_70")
 
     def test_rejections_before_cuda(self):
-        for kw in ({"fine_block": (7, 7)}, {"fine_block": (16,)}):
+        for kw in ({"level_blocks": [None, (7, 7)]}, {"level_blocks": [None, (16,)]}):
             with self.subTest(kw=kw), self.assertRaises(ValueError):
-                FixedPatchStepper(config("periodic"), BOUNDS, context=self.forbidden_context(), **kw)
+                FixedPatchStepper(config("periodic"), context=self.forbidden_context(),
+                                  refinements=[BOUNDS], **kw)
 
     def test_single_block_layout_allocates_no_empty_halo_tables(self):
         # A 1x1 non-periodic fine layout has zero halo pairs; CUDA rejects mem_alloc(0).
@@ -125,8 +126,8 @@ class BlockedFineCPU(unittest.TestCase):
                 patch.object(compiler, "compile_kernel"), patch.object(compiler, "cleanup_build_dir"), \
                 patch.object(compiler, "load_module", return_value=module), \
                 patch.object(cuda, "mem_alloc", side_effect=alloc), patch.object(cuda, "memcpy_htod"):
-            backend = FixedPatchStepper(config("periodic"), BOUNDS, context=context,
-                                        fine_block=FINE_BLOCKS[0])
+            backend = FixedPatchStepper(config("periodic"), context=context, refinements=[BOUNDS],
+                                        level_blocks=[None, FINE_BLOCKS[0]])
             self.assertEqual(len(backend.fine_layout.halo_dst), 0)
             self.assertIsNone(backend._levels[1].halo_dst)
             backend._gather_halo(backend._levels[1], Mock())  # no launch without pairs
@@ -177,8 +178,9 @@ class BlockedFineCPU(unittest.TestCase):
                 patch.object(cuda, "mem_alloc", side_effect=lambda size: Mock()), \
                 patch.object(cuda, "memcpy_htod"), \
                 patch.object(curved_links, "CurvedLinkSoA", side_effect=AssertionError("dense SoA built")):
-            backend = FixedPatchStepper(config("periodic"), BOUNDS, context=context,
-                                        fine_objects=objects, fine_block=FINE_BLOCKS[1])
+            backend = FixedPatchStepper(config("periodic"), context=context, refinements=[BOUNDS],
+                                        level_blocks=[None, FINE_BLOCKS[1]],
+                                        level_objects=[(), tuple(objects)])
             backend.initialize(state(NY, NX, 1), state(*backend.patch.fine_shape, 2))
         return backend, calls
 
@@ -289,8 +291,9 @@ class BlockedFineGPU(unittest.TestCase):
             results = []
             with CudaContext(0) as context:
                 for fine_block in (None, *FINE_BLOCKS):
-                    with FixedPatchStepper(cfg, BOUNDS, context=context, coarse_boundary=mode,
-                                           fine_block=fine_block) as backend:
+                    with FixedPatchStepper(cfg, context=context, coarse_boundary=mode,
+                                           refinements=[BOUNDS],
+                                           level_blocks=[None, fine_block]) as backend:
                         backend.initialize(g_coarse, g_fine)
                         backend.step(STEPS)
                         self.assertEqual(backend.step_count, STEPS)
@@ -318,8 +321,9 @@ class BlockedFineGPU(unittest.TestCase):
             results = []
             with CudaContext(0) as context:
                 for fine_block in (None, *FINE_BLOCKS):
-                    with FixedPatchStepper(cfg, BOUNDS, context=context, coarse_boundary=mode,
-                                           fine_objects=[circle()], fine_block=fine_block) as backend:
+                    with FixedPatchStepper(cfg, context=context, coarse_boundary=mode,
+                                           refinements=[BOUNDS], level_blocks=[None, fine_block],
+                                           level_objects=[(), (circle(),)]) as backend:
                         backend.initialize(g_coarse, g_fine)
                         backend.step(STEPS)
                         results.append((backend.download(), raw(backend)))
@@ -346,9 +350,9 @@ class BlockedFineGPU(unittest.TestCase):
                 results = []
                 with CudaContext(0) as context:
                     for fine_block in (None, *FINE_BLOCKS):
-                        with FixedPatchStepper(cfg, BOUNDS, context=context, coarse_boundary=mode,
-                                               fine_objects=[circle(actuation(speed))],
-                                               fine_block=fine_block) as backend:
+                        with FixedPatchStepper(cfg, context=context, coarse_boundary=mode,
+                                               refinements=[BOUNDS], level_blocks=[None, fine_block],
+                                               level_objects=[(), (circle(actuation(speed)),)]) as backend:
                             backend.initialize(g_coarse, g_fine)
                             backend.step(STEPS)
                             results.append((backend.download(), raw(backend)))

tests/validation/multigrid/test_refinement_followup.py

@@ -94,7 +94,8 @@ class FaultGuardsCPU(unittest.TestCase):
                              ("slot_reservoir", (12, 4, 20, 21))):
             with self.subTest(mode=mode, bounds=bounds):
                 with self.assertRaises(ValueError):
-                    implementation.FixedPatchStepper(cfg, bounds, context=context, coarse_boundary=mode)
+                    implementation.FixedPatchStepper(cfg, context=context, coarse_boundary=mode,
+                                                     refinements=[bounds])
                 context.activate.assert_not_called()
         # Both exact channel limits and the original periodic two-cell margin
         # must reach context activation, with no allocation or device required.
@@ -102,11 +103,14 @@ class FaultGuardsCPU(unittest.TestCase):
                              ("periodic", (2, 2, 6, 5))):
             with self.subTest(mode=mode, bounds=bounds):
                 with self.assertRaisesRegex(RuntimeError, "validated before CUDA"):
-                    implementation.FixedPatchStepper(cfg, bounds, context=context, coarse_boundary=mode)
+                    implementation.FixedPatchStepper(cfg, context=context, coarse_boundary=mode,
+                                                     refinements=[bounds])
 
     def fake_backend(self):
         backend = PeriodicPatchStepper.__new__(PeriodicPatchStepper)
-        backend.fine_layout = None  # dense fine storage
+        backend._layouts = [None, None]  # dense storage on both levels
+        backend._ddf_shifting = False  # unshifted on every level, as _check_storage expects
+        backend._level_cfgs = [LBMConfig(nx=16, ny=16, viscosity=.1)] * 2  # ddf_shifting off
         backend.ctx = Mock(activate=nullcontext)
         backend._lock = RLock()
         backend._status = "ready"
@@ -154,12 +158,23 @@ 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, (4, 4, 12, 12), context=context)
+                PeriodicPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)])
         p = implementation.FixedPatch2D.from_config(cfg, (4, 4, 12, 12))
-        with patch.object(cuda, "Stream"), patch.object(implementation.FixedPatch2D, "from_config",
-                                                       return_value=replace(p, tau_coarse=.9)):
-            with self.assertRaisesRegex(RuntimeError, "omega/tau"):
-                PeriodicPatchStepper(cfg, p.bounds, context=context)
+        from CelerisLab.lbm import hierarchy
+        bad = patch.object(implementation.FixedPatch2D, "from_config",
+                           return_value=replace(p, tau_coarse=.9))
+        # A pair tau inconsistent with its level config is rejected twice over, both before
+        # any device allocation or upload: first by the hierarchy chain check, and, if that
+        # is bypassed, by the per-level omega/tau check in _build_level.
+        with patch.object(cuda, "Stream"), 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])
+            with patch.object(hierarchy, "_check_chain"), \
+                    self.assertRaisesRegex(RuntimeError, "omega/tau"):
+                PeriodicPatchStepper(cfg, context=context, refinements=[p.bounds])
+            alloc.assert_not_called()
+            upload.assert_not_called()
         module = Mock()
         module.get_global.return_value = (Mock(), 16)
         with patch.object(cuda, "Stream"), patch.object(compiler, "generate_config"), \
@@ -167,7 +182,7 @@ 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, p.bounds, context=context)
+                PeriodicPatchStepper(cfg, context=context, refinements=[p.bounds])
             upload.assert_not_called()
 
 
@@ -241,7 +256,7 @@ class NormalBuildGPU(unittest.TestCase):
         max_error = max_bc_error = 0.0
         with CudaContext(0) as context:
             with patch.object(compiler, "generate_config", side_effect=record_config):
-                backend = implementation.FixedPatchStepper(cfg, bounds, context=context,
+                backend = implementation.FixedPatchStepper(cfg, context=context, refinements=[bounds],
                                                             coarse_boundary="slot_reservoir")
             with backend:
                 self.assertEqual(len(generated), 2)
@@ -311,7 +326,8 @@ class NormalBuildGPU(unittest.TestCase):
                             for a in (initial.coarse_f, initial.fine_f)))
         max_pop = max_drift = max_moment = 0.0
         with CudaContext(0) as context, PeriodicPatchStepper(
-                LBMConfig(nx=16, ny=16, viscosity=.1), (4, 4, 12, 12), context=context) as backend:
+                LBMConfig(nx=16, ny=16, viscosity=.1), context=context,
+                refinements=[(4, 4, 12, 12)]) as backend:
             backend.initialize(*postcollision(state, spec, maps))
             before = totals(backend.download(), maps)
             for step in range(1, 9):
@@ -342,7 +358,7 @@ 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, bounds, context=context) as backend:
+        with CudaContext(0) as context, PeriodicPatchStepper(cfg, context=context, refinements=[bounds]) as backend:
             self.assertEqual(backend.patch.fine_shape, (14, 16))
             p = backend.patch
             allocated = 2 * 9 * (17*13+16*14) * 4 + sum(a.nbytes for a in

tests/validation/multigrid/test_refinement_gpu.py

@@ -84,13 +84,13 @@ class CoupledGPU(unittest.TestCase):
 
         cases = (("dense_unshifted", False, {}),
                  ("blocked_shifted", True,
-                  dict(base_block=(4, 4), fine_block=(6, 6))))
+                  dict(level_blocks=[(4, 4), (6, 6)])))
         with CudaContext(0) as context:
             for label, shifted, storage in cases:
                 with self.subTest(storage=label):
                     cfg = LBMConfig(nx=16, ny=16, viscosity=.0192,
                                     ddf_shifting=shifted)
-                    with FixedPatchStepper(cfg, (4, 4, 12, 12), context=context,
+                    with FixedPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)],
                                            **storage) as backend:
                         self.assertAlmostEqual(backend.patch.tau_coarse, spec.tau_coarse)
                         self.assertAlmostEqual(backend.patch.tau_fine, spec.tau_fine)
@@ -148,7 +148,7 @@ class CoupledGPU(unittest.TestCase):
         maps = ref.build_maps(spec)
         with CudaContext(0) as context:
             with PeriodicPatchStepper(LBMConfig(nx=16, ny=16, viscosity=.1),
-                                      (4, 4, 12, 12), context=context) as backend:
+                                      context=context, refinements=[(4, 4, 12, 12)]) as backend:
                 backend.initialize(*postcollision(ref.make_state(spec), spec, maps))
                 coarse, fine = backend._levels
 
@@ -187,7 +187,7 @@ class CoupledGPU(unittest.TestCase):
 
         with CudaContext(0) as context:
             with patch.object(compiler, "compile_kernel", audit_compile):
-                backend = PeriodicPatchStepper(cfg, (4, 4, 12, 12), context=context)
+                backend = PeriodicPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)])
             with backend:
                 # Production allocations: four DDF arrays and four compact tables.
                 device_bytes = 2 * 9 * (16**2 + 24**2) * 4
@@ -270,7 +270,7 @@ class CoupledGPU(unittest.TestCase):
                 backend.download()
 
             # Compile and execute the actual non-audited entry as well: one step.
-            with PeriodicPatchStepper(cfg, (4, 4, 12, 12), context=context) as plain:
+            with PeriodicPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)]) as plain:
                 rest = postcollision(ref.make_state(spec), spec, maps)
                 plain.initialize(*rest)
                 plain.step()

tests/validation/multigrid/test_refinement_jets.py

@@ -41,8 +41,9 @@ def mocked(objects, jets, fine_block):
             patch.object(compiler, "load_module", return_value=module), \
             patch.object(cuda, "mem_alloc", side_effect=lambda size: Mock()), \
             patch.object(cuda, "memcpy_htod", htod):
-        backend = FixedPatchStepper(config("periodic"), BOUNDS, context=context,
-                                    fine_objects=objects, fine_block=fine_block, jets=jets)
+        backend = FixedPatchStepper(config("periodic"), context=context, refinements=[BOUNDS],
+                                    level_blocks=[None, fine_block], level_objects=[(), tuple(objects)],
+                                    level_jets=[(), tuple(jets)])
     return backend, htod
 
 
@@ -149,8 +150,9 @@ class JetStepperCPU(unittest.TestCase):
     def test_jet_overlapping_legacy_aperture_rejected_before_cuda(self):
         with patch.object(cuda, "Stream", side_effect=AssertionError("CUDA touched")):
             with self.assertRaisesRegex(ValueError, "SurfaceActuation"):
-                FixedPatchStepper(config("periodic"), BOUNDS, context=Mock(),
-                                  fine_objects=[circle(actuation(SPEED))], jets=[jet()])
+                FixedPatchStepper(config("periodic"), context=Mock(), refinements=[BOUNDS],
+                                  level_objects=[(), (circle(actuation(SPEED)),)],
+                                  level_jets=[(), (jet(),)])
 
 
 def run(mode, fine_block, *, objects, jets, switch=None):
@@ -158,8 +160,9 @@ def run(mode, fine_block, *, objects, jets, switch=None):
     cfg = config(mode)
     patch_ = FixedPatch2D.from_config(cfg, BOUNDS)
     with CudaContext(0) as context, FixedPatchStepper(
-            cfg, BOUNDS, context=context, coarse_boundary=mode, fine_objects=objects,
-            fine_block=fine_block, jets=jets) as backend:
+            cfg, context=context, coarse_boundary=mode, refinements=[BOUNDS],
+            level_blocks=[None, fine_block], level_objects=[(), tuple(objects)],
+            level_jets=[(), tuple(jets)]) as backend:
         backend.initialize(state(NY, NX, 1), state(*patch_.fine_shape, 2))
         if switch is None:
             backend.step(STEPS)

tests/validation/multigrid/test_refinement_mrt_gpu.py

@@ -42,8 +42,9 @@ class RefinementMRTGPU(unittest.TestCase):
                                     collision="MRT", ddf_shifting=shifted)
                     reference = None
                     for block in ((32, 48), (8, 8), (4, 1)):
-                        with FixedPatchStepper(cfg, (8, 6, 40, 26), context=context, coarse_boundary=boundary,
-                                               base_block=block, fine_block=(8, 8), fine_objects=(body,)) as backend:
+                        with FixedPatchStepper(cfg, context=context, coarse_boundary=boundary,
+                                               refinements=[(8, 6, 40, 26)], level_blocks=[block, (8, 8)],
+                                               level_objects=[(), (body,)]) as backend:
                             backend.initialize(*[state(*level.shape[1:]) for level in backend._levels])
                             backend.step(8)
                             raw = backend._download_raw()
@@ -63,8 +64,8 @@ class RefinementMRTGPU(unittest.TestCase):
             results = {}
             layouts = ((None, None), *((base, FINE_BLOCK) for base in (None, *BASE_BLOCKS)))
             for base_block, fine_block in layouts:
-                with FixedPatchStepper(cfg, BOUNDS, context=context, fine_block=fine_block,
-                                       base_block=base_block) as backend:
+                with FixedPatchStepper(cfg, context=context, refinements=[BOUNDS],
+                                       level_blocks=[base_block, fine_block]) as backend:
                     backend.initialize(*[fixture.state(*level.shape[1:], seed) for seed, level in enumerate(backend._levels)])
                     backend.step(4)
                     results[base_block, fine_block] = raw(backend)
@@ -75,9 +76,9 @@ class RefinementMRTGPU(unittest.TestCase):
     def test_shifted_all_blocked_three_level_mrt_smoke(self):
         """Per-level shear rate omega_l = 1/(3*2**l*nu + 1/2); finite ACTIVE leaves."""
         cfg = LBMConfig(nx=16, ny=16, viscosity=.1, collision="MRT", ddf_shifting=True)
-        kw = dict(fine_block=(4, 4), base_block=(4, 4), child=(8, 8, 16, 16), child_block=(4, 4))
+        kw = dict(refinements=[(4, 4, 12, 12), (8, 8, 16, 16)], level_blocks=[(4, 4)] * 3)
         with CudaContext(0) as context:
-            with FixedPatchStepper(cfg, (4, 4, 12, 12), context=context, **kw) as backend:
+            with FixedPatchStepper(cfg, context=context, **kw) as backend:
                 self.assertEqual(len(backend._level_cfgs), 3)
                 for level, level_cfg in enumerate(backend._level_cfgs):
                     checked = replace(level_cfg)

tests/validation/multigrid/test_refinement_multipatch.py

@@ -26,6 +26,12 @@ FACE = ((4, 4, 8, 12), (12, 4, 16, 12))
 S1 = ((4, 4, 12, 12), (20, 4, 28, 12))
 
 
+def levels(bounds, blocks=(None, None), objects=(), jets=(), **rest):
+    """Two-level constructor keywords: one L1 rectangle or set, per-level blocks, L1 bodies/Jets."""
+    return dict(refinements=[bounds], level_blocks=list(blocks),
+                level_objects=[(), tuple(objects)], level_jets=[(), tuple(jets)], **rest)
+
+
 def level_fine(patch_set, windows):
     """Level-wide fine array with each patch window filled from `windows`."""
     out = np.full((9, *patch_set.fine_shape), np.nan, np.float32)
@@ -45,21 +51,21 @@ class MultipatchCPU(unittest.TestCase):
     def test_rejections_before_cuda(self):
         cfg = config("periodic")
         context = object()  # never activated: every case must fail first
-        for kw in (dict(), dict(fine_block=(8, 4)), dict(base_block=(4, 4)),
-                   dict(fine_block=(8, 4), base_block=(4, 4), fine_objects=[circle()]),
-                   dict(fine_block=(5, 4), base_block=(4, 4))):
+        for kw in (dict(), dict(blocks=(None, (8, 4))), dict(blocks=((4, 4), None)),
+                   dict(blocks=((4, 4), (8, 4)), objects=[circle()]),
+                   dict(blocks=((4, 4), (5, 4)))):
             with self.subTest(kw=kw), self.assertRaises(ValueError):
-                FixedPatchStepper(cfg, ((4, 4, 8, 12), (14, 4, 18, 12)), context=context, **kw)
+                FixedPatchStepper(cfg, context=context, **levels(((4, 4, 8, 12), (14, 4, 18, 12)), **kw))
         with self.assertRaisesRegex(ValueError, "margin"):
-            FixedPatchStepper(cfg, ((1, 4, 8, 12), (10, 4, 14, 12)), context=context,
-                              fine_block=(8, 4), base_block=(4, 4))
+            FixedPatchStepper(cfg, context=context,
+                              **levels(((1, 4, 8, 12), (10, 4, 14, 12)), blocks=((4, 4), (8, 4))))
         from CelerisLab.body.jets import Jet, Parallel, Tube
         cfg32 = LBMConfig(nx=32, ny=16, viscosity=.1)
         span = Jet(Tube((5., 8.), 0., 22., .6), Parallel(0.), amplitude=0.)
         with self.assertRaisesRegex(ValueError, "one jet"):  # same obj_id cannot bypass it
-            FixedPatchStepper(cfg32, ((2, 2, 14, 14), (18, 2, 30, 14)), context=context,
-                              fine_block=(4, 4), base_block=(4, 4),
-                              fine_objects=[body(8., 8.), body(24., 8.)], jets=[span])
+            FixedPatchStepper(cfg32, context=context,
+                              **levels(((2, 2, 14, 14), (18, 2, 30, 14)), blocks=((4, 4), (4, 4)),
+                                       objects=[body(8., 8.), body(24., 8.)], jets=[span]))
 
 
 class MultipatchGPU(unittest.TestCase):
@@ -67,7 +73,7 @@ class MultipatchGPU(unittest.TestCase):
 
     def run_steps(self, context, cfg, bounds, coarse, fine, **kw):
         out = []
-        with FixedPatchStepper(cfg, bounds, context=context, **kw) as backend:
+        with FixedPatchStepper(cfg, context=context, **levels(bounds, **kw)) as backend:
             backend.initialize(coarse, fine)
             for step in self.STEPS:
                 backend.step(step - backend.step_count)
@@ -82,7 +88,7 @@ class MultipatchGPU(unittest.TestCase):
                 p = FixedPatch2D.from_config(cfg, BOUNDS)
                 s = FixedPatchSet2D.from_config(cfg, (BOUNDS,))
                 coarse, fine = state(NY, NX, 1), state(*p.fine_shape, 2)
-                kw = dict(coarse_boundary=mode, fine_block=(8, 4), base_block=(3, 4))
+                kw = dict(coarse_boundary=mode, blocks=((3, 4), (8, 4)))
                 old = self.run_steps(context, cfg, BOUNDS, coarse, fine, **kw)
                 new = self.run_steps(context, cfg, (BOUNDS,), coarse, level_fine(s, [fine]), **kw)
                 for step, a, b in zip(self.STEPS, old, new):
@@ -99,7 +105,7 @@ class MultipatchGPU(unittest.TestCase):
         one = FixedPatchSet2D.from_config(cfg16, (S1[0],))
         two = FixedPatchSet2D.from_config(cfg32, S1)
         coarse, fine = state(16, 16, 3), state(*one.patches[0].fine_shape, 4)
-        kw = dict(fine_block=(4, 4), base_block=(4, 4))
+        kw = dict(blocks=((4, 4), (4, 4)))
         with CudaContext(0) as context:
             ref = self.run_steps(context, cfg16, (S1[0],), coarse, level_fine(one, [fine]), **kw)
             tiled = np.concatenate([coarse, coarse], axis=2)
@@ -118,7 +124,7 @@ class MultipatchGPU(unittest.TestCase):
         s = FixedPatchSet2D.from_config(cfg, FACE)
         coarse = state(16, 24, 5)
         fine = level_fine(s, [state(*p.fine_shape, 6 + i) for i, p in enumerate(s.patches)])
-        kw = dict(fine_block=(4, 4), base_block=(4, 4))
+        kw = dict(blocks=((4, 4), (4, 4)))
         leaf = s.fine_kind == ACTIVE
         support = s.fine_layout((4, 4)).owned
         outer = support & (s.fine_kind == OUTER_GHOST)
@@ -164,7 +170,7 @@ class MultipatchBodiesGPU(unittest.TestCase):
 
     def run_steps(self, context, cfg, bounds, coarse, fine, switch=None, **kw):
         out = []
-        with FixedPatchStepper(cfg, bounds, context=context, **kw) as backend:
+        with FixedPatchStepper(cfg, context=context, **levels(bounds, **kw)) as backend:
             backend.initialize(coarse, fine)
             for step in self.STEPS:
                 if switch is not None and step == 8:
@@ -182,8 +188,7 @@ class MultipatchBodiesGPU(unittest.TestCase):
                 p = FixedPatch2D.from_config(cfg, BOUNDS)
                 s = FixedPatchSet2D.from_config(cfg, (BOUNDS,))
                 coarse, fine = state(NY, NX, 1), state(*p.fine_shape, 2)
-                kw = dict(coarse_boundary=mode, fine_block=(8, 4), base_block=(3, 4),
-                          fine_objects=[circle()])
+                kw = dict(coarse_boundary=mode, blocks=((3, 4), (8, 4)), objects=[circle()])
                 old = self.run_steps(context, cfg, BOUNDS, coarse, fine, **kw)
                 new = self.run_steps(context, cfg, (BOUNDS,), coarse, level_fine(s, [fine]), **kw)
                 for step, a, b in zip(self.STEPS, old, new):
@@ -202,17 +207,17 @@ class MultipatchBodiesGPU(unittest.TestCase):
         two = FixedPatchSet2D.from_config(cfg32, self.PATCHES)
         coarse, fine = state(16, 16, 3), state(*one.patches[0].fine_shape, 4)
         jet = lambda x: Jet(Tube((x, 8.), 0., 6., .6), Parallel(0.), amplitude=.002)
-        kw = dict(fine_block=(4, 4), base_block=(4, 4))
+        kw = dict(blocks=((4, 4), (4, 4)))
         with CudaContext(0) as context:
             for jets in ((), (jet(5.),)):
                 ref = self.run_steps(context, cfg16, self.PATCHES[:1], coarse, level_fine(one, [fine]),
                                      switch=[(0, -.001)] if jets else None,
-                                     fine_objects=[body(8., 8.)], jets=jets, **kw)
+                                     objects=[body(8., 8.)], jets=jets, **kw)
                 both = jets and (jet(5.), jet(21.))
                 got = self.run_steps(context, cfg32, self.PATCHES, np.concatenate([coarse, coarse], 2),
                                      level_fine(two, [fine, fine]),
                                      switch=[(0, -.001), (1, -.001)] if jets else None,
-                                     fine_objects=[body(8., 8., 5), body(24., 8., 5)],
+                                     objects=[body(8., 8., 5), body(24., 8., 5)],
                                      jets=both or (), **kw)
                 for step, a, b in zip(self.STEPS, ref, got):
                     label = f"jets={len(jets)} step {step}"

tests/validation/multigrid/test_refinement_three_level.py

@@ -27,7 +27,16 @@ from test_refinement_blocked_base import raw
 
 CFG = LBMConfig(nx=16, ny=16, viscosity=.1)
 L1, L2 = (4, 4, 12, 12), (8, 8, 16, 16)
-KW = dict(fine_block=(4, 4), base_block=(4, 4), child=L2, child_block=(4, 4))
+B = (4, 4)
+
+
+def levels(l1=L1, l2=L2, blocks=(B, B, B), objects=((), (), ()), jets=((), (), ())):
+    """Level-list keywords for the scalar L1 patch with one scalar L2 child."""
+    return dict(refinements=[l1, l2], level_blocks=list(blocks),
+                level_objects=list(objects), level_jets=list(jets))
+
+
+KW = levels()
 
 
 def child_body(spec=None):
@@ -52,26 +61,29 @@ def mocked_child():
             patch.object(compiler, "load_module", return_value=module), \
             patch.object(cuda, "mem_alloc", side_effect=lambda size: Mock()), \
             patch.object(cuda, "memcpy_htod"):
-        return FixedPatchStepper(CFG, L1, context=context, child_objects=[child_body()],
-                                 child_jets=[child_jet()], **KW)
+        return FixedPatchStepper(CFG, context=context,
+                                 **levels(objects=((), (), (child_body(),)), jets=((), (), (child_jet(),))))
 
 
 class ThreeLevelCPU(unittest.TestCase):
     def test_rejections_before_cuda(self):
         context = object()  # never activated: every case must fail first
-        bad = (dict(KW, child_block=None), dict(KW, fine_block=None),
-               dict(KW, fine_objects=[circle()]), dict(KW, child=(4, 8, 16, 16)),
-               dict(KW, child_block=(5, 4)))
+        bad = (levels(blocks=(B, B, None)), levels(blocks=(B, None, B)),
+               levels(objects=((), (circle(),), ())), levels(l2=(4, 8, 16, 16)),
+               levels(blocks=(B, B, (5, 4))))
         for kw in bad:
             with self.subTest(kw=kw), self.assertRaises(ValueError):
-                FixedPatchStepper(CFG, L1, context=context, **kw)
-        for kw in (dict(child_objects=[child_body()]), dict(child_jets=[child_jet()]),
-                   dict(KW, child_jets=[child_jet()])):
+                FixedPatchStepper(CFG, context=context, **kw)
+        # L2 bodies/Jets without an L2 level (one entry too many), and an L2 Jet without a body.
+        two_level = dict(refinements=[L1], level_blocks=[None, None])
+        for kw in (dict(two_level, level_objects=[(), (), (child_body(),)]),
+                   dict(two_level, level_jets=[(), (), (child_jet(),)]),
+                   levels(jets=((), (), (child_jet(),)))):
             with self.assertRaises(ValueError):
-                FixedPatchStepper(CFG, L1, context=context, **kw)
-        with self.assertRaises(ValueError):  # several L1 patches + child: not yet
-            FixedPatchStepper(LBMConfig(nx=32, ny=16, viscosity=.1), ((4, 4, 12, 12), (20, 4, 28, 12)),
-                              context=context, **KW)
+                FixedPatchStepper(CFG, context=context, **kw)
+        with self.assertRaises(ValueError):  # several L1 patches + scalar child: not yet
+            FixedPatchStepper(LBMConfig(nx=32, ny=16, viscosity=.1), context=context,
+                              **levels(l1=((4, 4, 12, 12), (20, 4, 28, 12))))
 
 
     def test_four_halo_bfl_steps_and_fresh_middle_feeds(self):
@@ -156,7 +168,7 @@ class ThreeLevelGPU(unittest.TestCase):
     def test_equilibrium_is_kept_on_every_level(self):
         from CelerisLab.cuda.context import CudaContext
         feq = np.asarray(compute_feq_d2q9(1.0, .03, -.02), np.float32)[:, None, None]
-        with CudaContext(0) as ctx, FixedPatchStepper(CFG, L1, context=ctx, **KW) as run:
+        with CudaContext(0) as ctx, FixedPatchStepper(CFG, context=ctx, **KW) as run:
             shapes = ((16, 16), run.patch.fine_shape, run.child_patch.fine_shape)
             run.initialize(*(np.broadcast_to(feq, (9, *s)).copy() for s in shapes))
             run.step(8)
@@ -169,7 +181,7 @@ class ThreeLevelGPU(unittest.TestCase):
 
     def test_nonequilibrium_masks_and_fresh_middle_feeds(self):
         from CelerisLab.cuda.context import CudaContext
-        with CudaContext(0) as ctx, FixedPatchStepper(CFG, L1, context=ctx, **KW) as run:
+        with CudaContext(0) as ctx, FixedPatchStepper(CFG, context=ctx, **KW) as run:
             p1, p2 = run.patch, run.child_patch
             run.initialize(state(16, 16, 1), state(*p1.fine_shape, 2), state(*p2.fine_shape, 3))
             f = run._levels[1]
@@ -205,8 +217,9 @@ class ThreeLevelBodyGPU(unittest.TestCase):
             CFG, velocity=0., wall_normal_velocity=.001, wall_slot_width=4,
             y_wall_bc="on_site_velocity", top_wall_bc="reservoir")
         with CudaContext(0) as ctx, FixedPatchStepper(
-                cfg, L1, context=ctx, coarse_boundary=mode, child_objects=[child_body(spec)],
-                child_jets=jets, **dict(KW, child_block=block)) as run:
+                cfg, context=ctx, coarse_boundary=mode,
+                **levels(blocks=(B, B, block), objects=((), (), (child_body(spec),)),
+                         jets=((), (), tuple(jets)))) as run:
             run.initialize(*(state(*level.shape[1:], i + 1) for i, level in enumerate(run._levels)))
             snapshots = []
             for stop in (0, 1, 2, 4, 8):

tests/validation/multigrid/test_refinement_three_level_multipatch_gpu.py

@@ -78,10 +78,10 @@ class ThreeLevelMultipatchGPU(unittest.TestCase):
     def run_case(self, ctx, cfg=CFG, parents=PARENTS, children=CHILDREN,
                  mode='periodic', blocks=((4, 4), (4, 4)), objects=(), drive=(), switch=False,
                  scalar_child=None):
-        kwargs = dict(child_rectangles_in_parent=children) if scalar_child is None else dict(child=scalar_child)
-        with FixedPatchStepper(config(cfg, mode), parents, context=ctx, coarse_boundary=mode,
-                base_block=(4, 4), fine_block=blocks[0], child_block=blocks[1],
-                child_objects=objects, child_jets=drive, **kwargs) as run:
+        child = children if scalar_child is None else scalar_child
+        with FixedPatchStepper(config(cfg, mode), context=ctx, coarse_boundary=mode,
+                refinements=[parents, child], level_blocks=[(4, 4), blocks[0], blocks[1]],
+                level_objects=[(), (), objects], level_jets=[(), (), drive]) as run:
             frame = frames(run)
             run.initialize(*(physical_state(level.shape[1:], *f)
                              for level, f in zip(run._levels, frame)))

tests/validation/multigrid/test_runtime_child_remap_gpu.py

@@ -26,9 +26,8 @@ FP64_ATOL = 3e-6
 
 
 def make(ctx):
-    return FixedPatchStepper(CFG, PARENTS, context=ctx, base_block=(4, 4),
-                             fine_block=(4, 4), child_block=(4, 4),
-                             child_rectangles_in_parent=A)
+    return FixedPatchStepper(CFG, context=ctx, refinements=[PARENTS, A],
+                             level_blocks=[(4, 4)] * 3)
 
 
 def initial(run, uniform):

tests/validation/multigrid/test_shifted_jets_gpu.py

@@ -136,8 +136,8 @@ class ShiftedJetsGPU(unittest.TestCase):
                   Parallel(0.),amplitude=.013)
         for rho in (.99,1.01):
             with self.subTest(rho=rho),CudaContext(0) as ctx:
-                with FixedPatchStepper(cfg,(8,6,24,18),context=ctx,base_block=(4,4),fine_block=(4,4),
-                        fine_objects=(obj,),jets=(whole,),observe_raw_exchange=True) as run:
+                with FixedPatchStepper(cfg,context=ctx,refinements=[(8,6,24,18)],level_blocks=[(4,4)]*2,
+                        level_objects=[(),(obj,)],level_jets=[(),(whole,)],observe_raw_exchange=True) as run:
                     run._initialize_raw(initial(run,rho,u=.013,v=0.))
                     expected=run._download_raw();ledger=Ledger(self,run,1)
                     self.assertTrue(run._level_boundaries[1].tables['aperture'].all())
@@ -153,7 +153,8 @@ class ShiftedJetsGPU(unittest.TestCase):
         obj=circle((16.,12.),2.15);j=drive((16.,12.),2.15)
         for rho in (.99,1.01):
             with self.subTest(rho=rho),CudaContext(0) as ctx,ExitStack() as owned:
-                settings=dict(bounds=(8,6,24,18),context=ctx,base_block=(4,4),fine_block=(4,4),fine_objects=(obj,),jets=(j,))
+                settings=dict(context=ctx,refinements=[(8,6,24,18)],level_blocks=[(4,4)]*2,
+                              level_objects=[(),(obj,)],level_jets=[(),(j,)])
                 measured=owned.enter_context(FixedPatchStepper(cfg,observe_raw_exchange=True,**settings))
                 plain=owned.enter_context(FixedPatchStepper(cfg,**settings))
                 measured._initialize_raw(initial(measured,rho));plain._initialize_raw(initial(plain,rho))
@@ -186,8 +187,9 @@ class ShiftedJetsGPU(unittest.TestCase):
         parents=((4,4,20,28),(24,4,44,28));a=((16,16,32,40),(56,16,72,40));b=(a[0],(60,16,76,40))
         obj=circle((12.,14.),.8);j=drive((12.,14.),.8)
         with CudaContext(0) as ctx,ExitStack() as owned:
-            old=owned.enter_context(FixedPatchStepper(cfg,parents,context=ctx,base_block=(4,4),fine_block=(4,4),
-                child_block=(4,4),child_rectangles_in_parent=a,child_objects=(obj,),child_jets=(j,),observe_raw_exchange=True))
+            old=owned.enter_context(FixedPatchStepper(cfg,context=ctx,refinements=[parents,a],
+                level_blocks=[(4,4)]*3,level_objects=[(),(),(obj,)],level_jets=[(),(),(j,)],
+                observe_raw_exchange=True))
             old._initialize_raw(initial(old,.99));ledger=Ledger(self,old,2)
             for speed in (.002,-.001):old.set_jet_amplitude(0,speed,level=2);ledger.step()
             before=old._download_raw();count=old.step_count

tests/validation/multigrid/test_shifted_remap_gpu.py

@@ -22,9 +22,8 @@ B=((20,16,36,40),)
 
 
 def make(ctx):
-    return FixedPatchStepper(CFG,PARENTS,context=ctx,base_block=(4,4),
-                             fine_block=(4,4),child_block=(4,4),
-                             child_rectangles_in_parent=A)
+    return FixedPatchStepper(CFG,context=ctx,refinements=[PARENTS,A],
+                             level_blocks=[(4,4)]*3)
 
 
 def initial(run):

tests/validation/run_dfg_re20.py

@@ -126,8 +126,8 @@ def run_case(a, h, case):
             cfg, pair, body, host = rr.host_geometry(a.source, h, a.collision)
             context = stack.enter_context(CudaContext(0))
             backend = stack.enter_context(FixedPatchStepper(
-                cfg, rr.PLACEMENTS["wide"], context=context, coarse_boundary="channel",
-                base_block=rr.BASE_BLOCK, fine_block=rr.FINE_BLOCK, fine_objects=(body,),
+                cfg, context=context, coarse_boundary="channel", refinements=[rr.PLACEMENTS["wide"]],
+                level_blocks=[rr.BASE_BLOCK, rr.FINE_BLOCK], level_objects=[(), (body,)],
                 observe_raw_exchange=True, observe_window_exchange=True))
             from CelerisLab.lbm.channel import channel_masks
             from CelerisLab.lbm.refinement import ACTIVE

tests/validation/run_jet_circle_cv.py

@@ -279,12 +279,11 @@ def run_case(c, ctx, output, provenance, continuation=False):
         PeriodicBlockStepper(fine_cfg, layout, context=ctx, objects=[fobj]) as uniform,
         FixedPatchStepper(
             cfg,
-            c["bounds"],
             context=ctx,
-            base_block=(8, 8),
-            fine_block=(8, 8),
-            fine_objects=[obj],
-            jets=jets,
+            refinements=[c["bounds"]],
+            level_blocks=[(8, 8), (8, 8)],
+            level_objects=[(), (obj,)],
+            level_jets=[(), tuple(jets)],
             observe_raw_exchange=True,
         ) as amr,
     ):

tests/validation/run_refined_dfg.py

@@ -383,13 +383,12 @@ def run_case(a, h, periodic, case):
             backend = stack.enter_context(
                 FixedPatchStepper(
                     cfg,
-                    PLACEMENTS[a.placement],
                     context=context,
                     coarse_boundary="channel",
-                    base_block=BASE_BLOCK,
-                    fine_block=FINE_BLOCK,
-                    fine_objects=(body,),
-                    jets=public_jets((80.5, 81.0), 20.0, a.jet_scenario),
+                    refinements=[PLACEMENTS[a.placement]],
+                    level_blocks=[BASE_BLOCK, FINE_BLOCK],
+                    level_objects=[(), (body,)],
+                    level_jets=[(), public_jets((80.5, 81.0), 20.0, a.jet_scenario)],
                     observe_raw_exchange=True,
                     **({"observe_window_exchange": True} if a.observation_mode == "window" else {}),
                 )

tests/validation/taylor_green/test_projected_pairs.py

@@ -249,19 +249,35 @@ class ProjectedPairsTests(unittest.TestCase):
         self.assertFalse(assess(incomplete)["comparisons"][3]["passed"])
 
     def test_pinned_build_sources_match_host_generated_inputs(self):
+        """The pinned fingerprints are what today's compiler generates from the qualified
+        NUMERICAL_REVISION kernels; the current kernels may legitimately differ."""
+        import tarfile
         from CelerisLab.cuda import compiler_v2
 
-        for size in (128, 256):
-            cfg = replace(run_case.config(size, 100), nx=10, ny=10)
-            cfg.validate()
-            root = compiler_v2.generate_config(cfg)
-            try:
-                actual = json.loads((Path(root) / ".celeris-build").read_text())
-                expected = build_metadata(size)
-                self.assertEqual(actual, {key: expected[key] for key in
-                                          ("source_sha256", "config", "n_objects")})
-            finally:
-                compiler_v2.cleanup_build_dir(root)
+        kernels = "src/CelerisLab/lbm/kernels"
+        if subprocess.run(["git", "-C", str(REPO), "cat-file", "-e",
+                           f"{NUMERICAL_REVISION}^{{commit}}"], capture_output=True).returncode:
+            self.fail(f"{NUMERICAL_REVISION} is not in this clone; the pinned build "
+                      "sources cannot be checked")
+        archive = subprocess.run(["git", "-C", str(REPO), "archive", "--format=tar",
+                                  NUMERICAL_REVISION, kernels],
+                                 capture_output=True, check=True).stdout
+        with tempfile.TemporaryDirectory() as snapshot:
+            with tarfile.open(fileobj=io.BytesIO(archive)) as tar:
+                tar.extractall(snapshot)
+            with patch.object(compiler_v2, "_KERNEL_DIR", str(Path(snapshot) / kernels)):
+                for size in (128, 256):
+                    with self.subTest(size=size):
+                        cfg = replace(run_case.config(size, 100), nx=10, ny=10)
+                        cfg.validate()
+                        root = compiler_v2.generate_config(cfg)
+                        try:
+                            actual = json.loads((Path(root) / ".celeris-build").read_text())
+                            expected = build_metadata(size)
+                            self.assertEqual(actual, {key: expected[key] for key in
+                                                      ("source_sha256", "config", "n_objects")})
+                        finally:
+                            compiler_v2.cleanup_build_dir(root)
 
     def test_source_preflight_requires_clean_exact_revision_and_tree(self):
         import oracle

tests/validation/time_refined_dfg.py

@@ -173,8 +173,9 @@ def time_refined(a, h, sched):
         cfg, pair, body, host = r.host_geometry(a.source, h, "MRT")
         context = stack.enter_context(CudaContext(0))
         backend = stack.enter_context(FixedPatchStepper(
-            cfg, r.BOUNDS, context=context, coarse_boundary="channel", base_block=r.BASE_BLOCK,
-            fine_block=r.FINE_BLOCK, fine_objects=(body,), observe_raw_exchange=True))
+            cfg, context=context, coarse_boundary="channel", refinements=[r.BOUNDS],
+            level_blocks=[r.BASE_BLOCK, r.FINE_BLOCK], level_objects=[(), (body,)],
+            observe_raw_exchange=True))
         masks = [channel_masks(pair.coarse_shape)[0] & ~pair.covered,  # as run_refined_dfg
                  (pair.fine_kind == ACTIVE) & ((host.flags.reshape(pair.fine_shape) & SOLID) == 0)]
         fresh = (r.initial_state(pair.coarse_shape, (0.0, 0.0), 1.0, root=True),

tests/validation/time_window_dfg.py

@@ -130,8 +130,8 @@ def main():
         cfg, pair, body, host = r.host_geometry(a.source, h, "MRT")
         context = stack.enter_context(CudaContext(0))
         backend = stack.enter_context(FixedPatchStepper(
-            cfg, r.BOUNDS, context=context, coarse_boundary="channel", base_block=r.BASE_BLOCK,
-            fine_block=r.FINE_BLOCK, fine_objects=(body,), observe_raw_exchange=True,
+            cfg, context=context, coarse_boundary="channel", refinements=[r.BOUNDS],
+            level_blocks=[r.BASE_BLOCK, r.FINE_BLOCK], level_objects=[(), (body,)], observe_raw_exchange=True,
             observe_window_exchange=True))
         masks = [channel_masks(pair.coarse_shape)[0] & ~pair.covered,
                  (pair.fine_kind == ACTIVE) & ((host.flags.reshape(pair.fine_shape) & SOLID) == 0)]