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PERF: only apply nanops rowwise optimization for narrow arrows #44566

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Merged
merged 4 commits into from
Nov 23, 2021
Merged

PERF: only apply nanops rowwise optimization for narrow arrows #44566

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PERF: only apply nanops rowwise optimization for narrow arrows
jorisvandenbossche Nov 21, 2021
3e6cba6
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jorisvandenbossche Nov 22, 2021
afdd07e
Merge remote-tracking branch 'upstream/master' into am-perf-nanops
jorisvandenbossche Nov 22, 2021
5f82b02
avoid divide by zero
jorisvandenbossche Nov 22, 2021
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6 changes: 5 additions & 1 deletion pandas/core/nanops.py
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Original file line number Diff line number Diff line change
Expand Up @@ -455,7 +455,8 @@ def _na_for_min_count(values: np.ndarray, axis: int | None) -> Scalar | np.ndarr
def maybe_operate_rowwise(func: F) -> F:
"""
NumPy operations on C-contiguous ndarrays with axis=1 can be
very slow. Operate row-by-row and concatenate the results.
very slow if axis 1 >> axis 0.
Operate row-by-row and concatenate the results.
"""

@functools.wraps(func)
Expand All @@ -464,6 +465,9 @@ def newfunc(values: np.ndarray, *, axis: int | None = None, **kwargs):
axis == 1
and values.ndim == 2
and values.flags["C_CONTIGUOUS"]
# only takes this path for wide arrays (long dataframes), for threshold see
# https://github.com/pandas-dev/pandas/pull/43311#issuecomment-974891737
and (values.shape[1] / 1000) > values.shape[0]
and values.dtype != object
and values.dtype != bool
):
Expand Down