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Avoid rechunking when preferred_method="blockwise" #394

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Merged
merged 3 commits into from
Sep 16, 2024
Merged

Avoid rechunking when preferred_method="blockwise" #394

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c1b5c1c
Avoid rechunking when preferred_method="blockwise"
dcherian Sep 15, 2024
40efff2
Add test
dcherian Sep 16, 2024
c686294
fix
dcherian Sep 16, 2024
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4 changes: 3 additions & 1 deletion flox/core.py
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Original file line number Diff line number Diff line change
Expand Up @@ -642,6 +642,7 @@ def rechunk_for_blockwise(array: DaskArray, axis: T_Axis, labels: np.ndarray) ->
DaskArray
Rechunked array
"""
# TODO: this should be unnecessary?
labels = factorize_((labels,), axes=())[0]
chunks = array.chunks[axis]
newchunks = _get_optimal_chunks_for_groups(chunks, labels)
Expand Down Expand Up @@ -2623,7 +2624,8 @@ def groupby_reduce(

partial_agg = partial(dask_groupby_agg, **kwargs)

if method == "blockwise" and by_.ndim == 1:
# if preferred method is already blockwise, no need to rechunk
if preferred_method != "blockwise" and method == "blockwise" and by_.ndim == 1:
array = rechunk_for_blockwise(array, axis=-1, labels=by_)

result, groups = partial_agg(
Expand Down
9 changes: 9 additions & 0 deletions tests/test_core.py
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Expand Up @@ -1997,3 +1997,12 @@ def test_agg_dtypes(func, engine):
)
expected = _get_array_func(func)(counts, dtype="uint8")
assert actual.dtype == np.uint8 == expected.dtype


@requires_dask
def test_blockwise_avoid_rechunk():
array = dask.array.zeros((6,), chunks=(2, 4), dtype=np.int64)
by = np.array(["1", "1", "0", "", "0", ""], dtype="<U1")
actual, groups = groupby_reduce(array, by, func="first")
assert_equal(groups, ["", "0", "1"])
assert_equal(actual, [0, 0, 0])