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Remove unneeded copies in rechunk #878

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Merged
tomwhite merged 1 commit into from
Feb 2, 2026
Merged

Remove unneeded copies in rechunk #878

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3 changes: 2 additions & 1 deletion cubed/core/ops.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1100,7 +1100,8 @@ def _rechunk_plan(x, chunks, *, min_mem=None):
yield read_chunks, target_chunks_
else:
yield read_chunks, int_chunks
yield write_chunks, target_chunks_
if last_stage:
yield write_chunks, target_chunks_


def _rechunk(x, copy_chunks, target_chunks):
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8 changes: 2 additions & 6 deletions cubed/tests/test_rechunk.py
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Expand Up @@ -60,8 +60,8 @@ def test_rechunk_era5(
if d.get("op_name", None) == "rechunk"
]

# each stage has two ops due to intermediate store
assert len(rechunks) == expected_num_stages * 2
# number of rechunk copy ops is one more than the number of stages
assert len(rechunks) == expected_num_stages + 1

max_input_blocks = max(
d["pipeline"].config.num_input_blocks[0] for _, d in rechunks
Expand Down Expand Up @@ -95,13 +95,9 @@ def test_rechunk_era5_chunk_sizes(spec):
rechunk_plan = list(_rechunk_plan(a, target_chunks))
assert rechunk_plan == [
((93, 721, 1440), (93, 240, 480)),
((465, 240, 480), (465, 240, 480)),
((465, 240, 480), (465, 120, 240)),
((2325, 120, 240), (2325, 120, 240)),
((2325, 120, 240), (2325, 40, 120)),
((11625, 40, 120), (11625, 40, 120)),
((11625, 40, 120), (11625, 20, 60)),
((58125, 20, 60), (58125, 20, 60)),
((58125, 20, 60), (58125, 10, 30)),
((350640, 10, 30), (350640, 10, 10)),
]
Expand Down