Revert "ENH: Add method='table' for EWM.mean (#42273)" (#42302)

This reverts commit bba53fc.

Author: simonjayhawkins

asv_bench/benchmarks/rolling.py

@@ -296,8 +296,5 @@ def time_apply(self, method):
             table_method_func, raw=True, engine="numba"
         )
 
-    def time_ewm_mean(self, method):
-        self.df.ewm(1, method=method).mean(engine="numba")
-
 
 from .pandas_vb_common import setup  # noqa: F401 isort:skip

doc/source/whatsnew/v1.3.0.rst

@@ -240,7 +240,7 @@ For example:
 Other enhancements
 ^^^^^^^^^^^^^^^^^^
 
-- :meth:`DataFrame.rolling`, :meth:`Series.rolling`, :meth:`DataFrame.expanding`, :meth:`Series.ewm`, :meth:`DataFrame.ewm`, :meth:`Series.expanding` now support a ``method`` argument with a ``'table'`` option that performs the windowing operation over an entire :class:`DataFrame`. See :ref:`Window Overview <window.overview>` for performance and functional benefits (:issue:`15095`, :issue:`38995`, :issue:`42273`)
+- :meth:`DataFrame.rolling`, :meth:`Series.rolling`, :meth:`DataFrame.expanding`, and :meth:`Series.expanding` now support a ``method`` argument with a ``'table'`` option that performs the windowing operation over an entire :class:`DataFrame`. See :ref:`Window Overview <window.overview>` for performance and functional benefits (:issue:`15095`, :issue:`38995`)
 - :class:`.ExponentialMovingWindow` now support a ``online`` method that can perform ``mean`` calculations in an online fashion. See :ref:`Window Overview <window.overview>` (:issue:`41673`)
 - Added :meth:`MultiIndex.dtypes` (:issue:`37062`)
 - Added ``end`` and ``end_day`` options for the ``origin`` argument in :meth:`DataFrame.resample` (:issue:`37804`)

pandas/core/generic.py

@@ -10904,7 +10904,6 @@ def ewm(
         ignore_na: bool_t = False,
         axis: Axis = 0,
         times: str | np.ndarray | FrameOrSeries | None = None,
-        method: str = "single",
     ) -> ExponentialMovingWindow:
         axis = self._get_axis_number(axis)
         # error: Value of type variable "FrameOrSeries" of "ExponentialMovingWindow"
@@ -10920,7 +10919,6 @@ def ewm(
             ignore_na=ignore_na,
             axis=axis,
             times=times,
-            method=method,
         )
 
     # ----------------------------------------------------------------------

pandas/core/window/ewm.py

@@ -40,10 +40,7 @@
     ExponentialMovingWindowIndexer,
     GroupbyIndexer,
 )
-from pandas.core.window.numba_ import (
-    generate_ewma_numba_table_func,
-    generate_numba_ewma_func,
-)
+from pandas.core.window.numba_ import generate_numba_ewma_func
 from pandas.core.window.online import (
     EWMMeanState,
     generate_online_numba_ewma_func,
@@ -203,16 +200,6 @@ class ExponentialMovingWindow(BaseWindow):
         If 1-D array like, a sequence with the same shape as the observations.
 
         Only applicable to ``mean()``.
-    method : str {'single', 'table'}, default 'single'
-        Execute the rolling operation per single column or row (``'single'``)
-        or over the entire object (``'table'``).
-
-        This argument is only implemented when specifying ``engine='numba'``
-        in the method call.
-
-        Only applicable to ``mean()``
-
-        .. versionadded:: 1.3.0
 
     Returns
     -------
@@ -271,7 +258,6 @@ class ExponentialMovingWindow(BaseWindow):
         "ignore_na",
         "axis",
         "times",
-        "method",
     ]
 
     def __init__(
@@ -286,7 +272,6 @@ def __init__(
         ignore_na: bool = False,
         axis: Axis = 0,
         times: str | np.ndarray | FrameOrSeries | None = None,
-        method: str = "single",
         *,
         selection=None,
     ):
@@ -296,7 +281,7 @@ def __init__(
             on=None,
             center=False,
             closed=None,
-            method=method,
+            method="single",
             axis=axis,
             selection=selection,
         )
@@ -452,19 +437,12 @@ def aggregate(self, func, *args, **kwargs):
     )
     def mean(self, *args, engine=None, engine_kwargs=None, **kwargs):
         if maybe_use_numba(engine):
-            if self.method == "single":
-                ewma_func = generate_numba_ewma_func(
-                    engine_kwargs, self._com, self.adjust, self.ignore_na, self._deltas
-                )
-                numba_cache_key = (lambda x: x, "ewma")
-            else:
-                ewma_func = generate_ewma_numba_table_func(
-                    engine_kwargs, self._com, self.adjust, self.ignore_na, self._deltas
-                )
-                numba_cache_key = (lambda x: x, "ewma_table")
+            ewma_func = generate_numba_ewma_func(
+                engine_kwargs, self._com, self.adjust, self.ignore_na, self._deltas
+            )
             return self._apply(
                 ewma_func,
-                numba_cache_key=numba_cache_key,
+                numba_cache_key=(lambda x: x, "ewma"),
             )
         elif engine in ("cython", None):
             if engine_kwargs is not None:

pandas/core/window/numba_.py

@@ -248,83 +248,3 @@ def nan_agg_with_axis(table):
         return result
 
     return nan_agg_with_axis
-
-
-def generate_ewma_numba_table_func(
-    engine_kwargs: dict[str, bool] | None,
-    com: float,
-    adjust: bool,
-    ignore_na: bool,
-    deltas: np.ndarray,
-):
-    """
-    Generate a numba jitted ewma function applied table wise specified
-    by values from engine_kwargs.
-
-    Parameters
-    ----------
-    engine_kwargs : dict
-        dictionary of arguments to be passed into numba.jit
-    com : float
-    adjust : bool
-    ignore_na : bool
-    deltas : numpy.ndarray
-
-    Returns
-    -------
-    Numba function
-    """
-    nopython, nogil, parallel = get_jit_arguments(engine_kwargs)
-
-    cache_key = (lambda x: x, "ewma_table")
-    if cache_key in NUMBA_FUNC_CACHE:
-        return NUMBA_FUNC_CACHE[cache_key]
-
-    numba = import_optional_dependency("numba")
-
-    @numba.jit(nopython=nopython, nogil=nogil, parallel=parallel)
-    def ewma_table(
-        values: np.ndarray,
-        begin: np.ndarray,
-        end: np.ndarray,
-        minimum_periods: int,
-    ) -> np.ndarray:
-        alpha = 1.0 / (1.0 + com)
-        old_wt_factor = 1.0 - alpha
-        new_wt = 1.0 if adjust else alpha
-        old_wt = np.ones(values.shape[0])
-
-        result = np.empty(values.shape)
-        weighted_avg = values[0].copy()
-        nobs = (~np.isnan(weighted_avg)).astype(np.int64)
-        result[0] = np.where(nobs >= minimum_periods, weighted_avg, np.nan)
-
-        for i in range(1, len(values)):
-            cur = values[i]
-            is_observations = ~np.isnan(cur)
-            nobs += is_observations.astype(np.int64)
-            for j in numba.prange(len(cur)):
-                if not np.isnan(weighted_avg[j]):
-                    if is_observations[j] or not ignore_na:
-
-                        # note that len(deltas) = len(vals) - 1 and deltas[i] is to be
-                        # used in conjunction with vals[i+1]
-                        old_wt[j] *= old_wt_factor ** deltas[j - 1]
-                        if is_observations[j]:
-                            # avoid numerical errors on constant series
-                            if weighted_avg[j] != cur[j]:
-                                weighted_avg[j] = (
-                                    (old_wt[j] * weighted_avg[j]) + (new_wt * cur[j])
-                                ) / (old_wt[j] + new_wt)
-                            if adjust:
-                                old_wt[j] += new_wt
-                            else:
-                                old_wt[j] = 1.0
-                elif is_observations[j]:
-                    weighted_avg[j] = cur[j]
-
-            result[i] = np.where(nobs >= minimum_periods, weighted_avg, np.nan)
-
-        return result
-
-    return ewma_table

pandas/tests/window/test_numba.py

@@ -304,16 +304,3 @@ def test_table_method_expanding_methods(
             engine_kwargs=engine_kwargs, engine="numba"
         )
         tm.assert_frame_equal(result, expected)
-
-    def test_table_method_ewm(self, axis, nogil, parallel, nopython):
-        engine_kwargs = {"nogil": nogil, "parallel": parallel, "nopython": nopython}
-
-        df = DataFrame(np.eye(3))
-
-        result = df.ewm(com=1, method="table", axis=axis).mean(
-            engine_kwargs=engine_kwargs, engine="numba"
-        )
-        expected = df.ewm(com=1, method="single", axis=axis).mean(
-            engine_kwargs=engine_kwargs, engine="numba"
-        )
-        tm.assert_frame_equal(result, expected)