PERF: vectorize _range_from_fields and _assemble_from_unit_mappings#65195
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jbrockmendel wants to merge 1 commit intopandas-dev:mainfrom
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PERF: vectorize _range_from_fields and _assemble_from_unit_mappings#65195jbrockmendel wants to merge 1 commit intopandas-dev:mainfrom
jbrockmendel wants to merge 1 commit intopandas-dev:mainfrom
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Add period_ordinals_from_fields Cython function that converts arrays of year/month/day/hour/minute/second fields to period ordinals in a single C-level loop, replacing the Python-space list-append loop in _range_from_fields. Reuse the same function in to_datetime's _assemble_from_unit_mappings with freq=FR_US to construct datetime64[us] directly from field arrays, avoiding the object-dtype round-trip through ensure_object + array_strptime with format="%Y%m%d". Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
period_ordinals_from_fieldsCython function that converts arrays of date/time fields to period ordinals in a single C-level loop, with optional date validation_range_from_fieldsto call the new Cython function instead of looping in Python-space and appending to a list; vectorize the quarter-to-calendar-month conversion with numpy ops_assemble_from_unit_mappingswithfreq=FR_USto constructdatetime64[us]directly from field arrays, avoiding the object-dtype round-trip throughensure_object+array_strptimewithformat="%Y%m%d"PeriodIndex.from_fields(2k monthly)PeriodIndex.from_fields(100k monthly)to_datetime(DataFrame)100k unique datesto_datetime(DataFrame)100k repeated datesThe old
to_datetime(DataFrame)path relied on_maybe_cachefor repeated values but degraded to ~15ms with unique dates due to per-elementstr()+ strptime. The new path is uniformly fast.Test plan
pandas/tests/indexes/period/test_constructors.py(108 + 3 new tests pass)pandas/tests/tools/test_to_datetime.py(939 + 9 new tests pass)pandas/tests/indexes/period/(466 tests pass)pandas/tests/arrays/period/(40 tests pass)New tests cover: non-DEC quarter fiscal year, all-6-field hourly periods, empty arrays, leap-year Feb 29 validation, invalid day-of-month (raise + coerce), fractional float coerce, empty DataFrame, UTC with time fields.
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