Optimize array_equivalent for NDFrame.equals (#35328)

Author: TomAugspurger

pandas/core/dtypes/missing.py

@@ -355,7 +355,9 @@ def _isna_compat(arr, fill_value=np.nan) -> bool:
     return True
 
 
-def array_equivalent(left, right, strict_nan: bool = False) -> bool:
+def array_equivalent(
+    left, right, strict_nan: bool = False, dtype_equal: bool = False
+) -> bool:
     """
     True if two arrays, left and right, have equal non-NaN elements, and NaNs
     in corresponding locations.  False otherwise. It is assumed that left and
@@ -368,6 +370,12 @@ def array_equivalent(left, right, strict_nan: bool = False) -> bool:
     left, right : ndarrays
     strict_nan : bool, default False
         If True, consider NaN and None to be different.
+    dtype_equal : bool, default False
+        Whether `left` and `right` are known to have the same dtype
+        according to `is_dtype_equal`. Some methods like `BlockManager.equals`.
+        require that the dtypes match. Setting this to ``True`` can improve
+        performance, but will give different results for arrays that are
+        equal but different dtypes.
 
     Returns
     -------
@@ -391,43 +399,28 @@ def array_equivalent(left, right, strict_nan: bool = False) -> bool:
     if left.shape != right.shape:
         return False
 
+    if dtype_equal:
+        # fastpath when we require that the dtypes match (Block.equals)
+        if is_float_dtype(left.dtype) or is_complex_dtype(left.dtype):
+            return _array_equivalent_float(left, right)
+        elif is_datetimelike_v_numeric(left.dtype, right.dtype):
+            return False
+        elif needs_i8_conversion(left.dtype):
+            return _array_equivalent_datetimelike(left, right)
+        elif is_string_dtype(left.dtype):
+            # TODO: fastpath for pandas' StringDtype
+            return _array_equivalent_object(left, right, strict_nan)
+        else:
+            return np.array_equal(left, right)
+
+    # Slow path when we allow comparing different dtypes.
     # Object arrays can contain None, NaN and NaT.
     # string dtypes must be come to this path for NumPy 1.7.1 compat
     if is_string_dtype(left.dtype) or is_string_dtype(right.dtype):
-
-        if not strict_nan:
-            # isna considers NaN and None to be equivalent.
-            return lib.array_equivalent_object(
-                ensure_object(left.ravel()), ensure_object(right.ravel())
-            )
-
-        for left_value, right_value in zip(left, right):
-            if left_value is NaT and right_value is not NaT:
-                return False
-
-            elif left_value is libmissing.NA and right_value is not libmissing.NA:
-                return False
-
-            elif isinstance(left_value, float) and np.isnan(left_value):
-                if not isinstance(right_value, float) or not np.isnan(right_value):
-                    return False
-            else:
-                try:
-                    if np.any(np.asarray(left_value != right_value)):
-                        return False
-                except TypeError as err:
-                    if "Cannot compare tz-naive" in str(err):
-                        # tzawareness compat failure, see GH#28507
-                        return False
-                    elif "boolean value of NA is ambiguous" in str(err):
-                        return False
-                    raise
-        return True
+        return _array_equivalent_object(left, right, strict_nan)
 
     # NaNs can occur in float and complex arrays.
     if is_float_dtype(left.dtype) or is_complex_dtype(left.dtype):
-
-        # empty
         if not (np.prod(left.shape) and np.prod(right.shape)):
             return True
         return ((left == right) | (isna(left) & isna(right))).all()
@@ -452,6 +445,45 @@ def array_equivalent(left, right, strict_nan: bool = False) -> bool:
     return np.array_equal(left, right)
 
 
+def _array_equivalent_float(left, right):
+    return ((left == right) | (np.isnan(left) & np.isnan(right))).all()
+
+
+def _array_equivalent_datetimelike(left, right):
+    return np.array_equal(left.view("i8"), right.view("i8"))
+
+
+def _array_equivalent_object(left, right, strict_nan):
+    if not strict_nan:
+        # isna considers NaN and None to be equivalent.
+        return lib.array_equivalent_object(
+            ensure_object(left.ravel()), ensure_object(right.ravel())
+        )
+
+    for left_value, right_value in zip(left, right):
+        if left_value is NaT and right_value is not NaT:
+            return False
+
+        elif left_value is libmissing.NA and right_value is not libmissing.NA:
+            return False
+
+        elif isinstance(left_value, float) and np.isnan(left_value):
+            if not isinstance(right_value, float) or not np.isnan(right_value):
+                return False
+        else:
+            try:
+                if np.any(np.asarray(left_value != right_value)):
+                    return False
+            except TypeError as err:
+                if "Cannot compare tz-naive" in str(err):
+                    # tzawareness compat failure, see GH#28507
+                    return False
+                elif "boolean value of NA is ambiguous" in str(err):
+                    return False
+                raise
+    return True
+
+
 def _infer_fill_value(val):
     """
     infer the fill value for the nan/NaT from the provided

pandas/core/internals/managers.py

@@ -1436,7 +1436,7 @@ def equals(self, other: "BlockManager") -> bool:
                 return array_equivalent(left, right)
 
         for i in range(len(self.items)):
-            # Check column-wise, return False if any column doesnt match
+            # Check column-wise, return False if any column doesn't match
             left = self.iget_values(i)
             right = other.iget_values(i)
             if not is_dtype_equal(left.dtype, right.dtype):
@@ -1445,7 +1445,7 @@ def equals(self, other: "BlockManager") -> bool:
                 if not left.equals(right):
                     return False
             else:
-                if not array_equivalent(left, right):
+                if not array_equivalent(left, right, dtype_equal=True):
                     return False
         return True
 

pandas/tests/dtypes/test_missing.py

@@ -300,50 +300,80 @@ def test_period(self):
         tm.assert_series_equal(notna(s), ~exp)
 
 
-def test_array_equivalent():
-    assert array_equivalent(np.array([np.nan, np.nan]), np.array([np.nan, np.nan]))
+@pytest.mark.parametrize("dtype_equal", [True, False])
+def test_array_equivalent(dtype_equal):
     assert array_equivalent(
-        np.array([np.nan, 1, np.nan]), np.array([np.nan, 1, np.nan])
+        np.array([np.nan, np.nan]), np.array([np.nan, np.nan]), dtype_equal=dtype_equal
+    )
+    assert array_equivalent(
+        np.array([np.nan, 1, np.nan]),
+        np.array([np.nan, 1, np.nan]),
+        dtype_equal=dtype_equal,
     )
     assert array_equivalent(
         np.array([np.nan, None], dtype="object"),
         np.array([np.nan, None], dtype="object"),
+        dtype_equal=dtype_equal,
     )
     # Check the handling of nested arrays in array_equivalent_object
     assert array_equivalent(
         np.array([np.array([np.nan, None], dtype="object"), None], dtype="object"),
         np.array([np.array([np.nan, None], dtype="object"), None], dtype="object"),
+        dtype_equal=dtype_equal,
     )
     assert array_equivalent(
         np.array([np.nan, 1 + 1j], dtype="complex"),
         np.array([np.nan, 1 + 1j], dtype="complex"),
+        dtype_equal=dtype_equal,
     )
     assert not array_equivalent(
         np.array([np.nan, 1 + 1j], dtype="complex"),
         np.array([np.nan, 1 + 2j], dtype="complex"),
+        dtype_equal=dtype_equal,
+    )
+    assert not array_equivalent(
+        np.array([np.nan, 1, np.nan]),
+        np.array([np.nan, 2, np.nan]),
+        dtype_equal=dtype_equal,
+    )
+    assert not array_equivalent(
+        np.array(["a", "b", "c", "d"]), np.array(["e", "e"]), dtype_equal=dtype_equal
+    )
+    assert array_equivalent(
+        Float64Index([0, np.nan]), Float64Index([0, np.nan]), dtype_equal=dtype_equal
     )
     assert not array_equivalent(
-        np.array([np.nan, 1, np.nan]), np.array([np.nan, 2, np.nan])
+        Float64Index([0, np.nan]), Float64Index([1, np.nan]), dtype_equal=dtype_equal
+    )
+    assert array_equivalent(
+        DatetimeIndex([0, np.nan]), DatetimeIndex([0, np.nan]), dtype_equal=dtype_equal
+    )
+    assert not array_equivalent(
+        DatetimeIndex([0, np.nan]), DatetimeIndex([1, np.nan]), dtype_equal=dtype_equal
+    )
+    assert array_equivalent(
+        TimedeltaIndex([0, np.nan]),
+        TimedeltaIndex([0, np.nan]),
+        dtype_equal=dtype_equal,
     )
-    assert not array_equivalent(np.array(["a", "b", "c", "d"]), np.array(["e", "e"]))
-    assert array_equivalent(Float64Index([0, np.nan]), Float64Index([0, np.nan]))
-    assert not array_equivalent(Float64Index([0, np.nan]), Float64Index([1, np.nan]))
-    assert array_equivalent(DatetimeIndex([0, np.nan]), DatetimeIndex([0, np.nan]))
-    assert not array_equivalent(DatetimeIndex([0, np.nan]), DatetimeIndex([1, np.nan]))
-    assert array_equivalent(TimedeltaIndex([0, np.nan]), TimedeltaIndex([0, np.nan]))
     assert not array_equivalent(
-        TimedeltaIndex([0, np.nan]), TimedeltaIndex([1, np.nan])
+        TimedeltaIndex([0, np.nan]),
+        TimedeltaIndex([1, np.nan]),
+        dtype_equal=dtype_equal,
     )
     assert array_equivalent(
         DatetimeIndex([0, np.nan], tz="US/Eastern"),
         DatetimeIndex([0, np.nan], tz="US/Eastern"),
+        dtype_equal=dtype_equal,
     )
     assert not array_equivalent(
         DatetimeIndex([0, np.nan], tz="US/Eastern"),
         DatetimeIndex([1, np.nan], tz="US/Eastern"),
+        dtype_equal=dtype_equal,
     )
+    # The rest are not dtype_equal
     assert not array_equivalent(
-        DatetimeIndex([0, np.nan]), DatetimeIndex([0, np.nan], tz="US/Eastern")
+        DatetimeIndex([0, np.nan]), DatetimeIndex([0, np.nan], tz="US/Eastern"),
     )
     assert not array_equivalent(
         DatetimeIndex([0, np.nan], tz="CET"),
@@ -353,6 +383,11 @@ def test_array_equivalent():
     assert not array_equivalent(DatetimeIndex([0, np.nan]), TimedeltaIndex([0, np.nan]))
 
 
+def test_array_equivalent_different_dtype_but_equal():
+    # Unclear if this is exposed anywhere in the public-facing API
+    assert array_equivalent(np.array([1, 2]), np.array([1.0, 2.0]))
+
+
 @pytest.mark.parametrize(
     "lvalue, rvalue",
     [