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[RAMSES] Optimisation: fast bbox rejection when finding intersecting domains #5379

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Merged
cphyc merged 2 commits into from
Mar 31, 2026
Merged

[RAMSES] Optimisation: fast bbox rejection when finding intersecting domains #5379

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a033c07
add bbox rejection for finding cpu intersections with a YTRegion
AnatoleStorck Feb 13, 2026
e1524be
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Feb 25, 2026
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14 changes: 12 additions & 2 deletions yt/frontends/ramses/hilbert.py
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Original file line number Diff line number Diff line change
Expand Up @@ -75,21 +75,31 @@ def get_intersecting_cpus(
dx_cond: float | None = None,
factor: float = 4.0,
bound_keys: Optional["np.ndarray[Any, np.dtype[np.float64]]"] = None,
bbox: Optional[Any] = None,
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@cphyc cphyc Feb 14, 2026

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I just realised, but Optional[Any] should probably be replaced by Optional[npt.NDArray] or even Optional[npt.NDArray[float]] (you'd need import numpy.testing as npt, see e.g. #5349).

) -> set[int]:
"""
Find the subset of CPUs that intersect the bbox in a recursive fashion.
"""
if bbox is None:
bbox = region.get_bbox()
if LE is None:
LE = np.array([0, 0, 0], dtype="d")
if dx_cond is None:
bbox = region.get_bbox()
dx_cond = float((bbox[1] - bbox[0]).min().to("code_length"))
if bound_keys is None:
ncpu = ds.parameters["ncpu"]
bound_keys = np.empty(ncpu + 1, dtype="float64")
bound_keys[:ncpu] = [ds.hilbert_indices[icpu + 1][0] for icpu in range(ncpu)]
bound_keys[ncpu] = ds.hilbert_indices[ncpu][1]

# bbox rejection to avoid expensive selector checks. (greatly improves performance for small disks)
bbox_min = bbox[0].to("code_length").d
bbox_max = bbox[1].to("code_length").d
cube_min = LE
cube_max = LE + dx
if np.any(cube_max < bbox_min) or np.any(cube_min > bbox_max):
return set()

# If the current dx is smaller than the smallest size of the bbox
if dx < dx_cond / factor:
# Finish recursion
Expand All @@ -111,7 +121,7 @@ def get_intersecting_cpus(
if bbox_intersects(region.selector, LE_new, dx):
ret.update(
get_intersecting_cpus(
ds, region, LE_new, dx, dx_cond, factor, bound_keys
ds, region, LE_new, dx, dx_cond, factor, bound_keys, bbox
)
)
return ret
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