From 226fd426c622c3a2a1eed83e5662e659877df7b9 Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Wed, 15 Apr 2020 07:57:01 -0700
Subject: [PATCH] REF: simplify broadcasting code

---
 pandas/core/internals/managers.py | 16 +++++----
 pandas/core/ops/__init__.py       |  4 ++-
 pandas/core/ops/array_ops.py      | 56 +------------------------------
 3 files changed, 13 insertions(+), 63 deletions(-)

diff --git a/pandas/core/internals/managers.py b/pandas/core/internals/managers.py
index e693341d10a55..04089e81db331 100644
--- a/pandas/core/internals/managers.py
+++ b/pandas/core/internals/managers.py
@@ -390,11 +390,7 @@ def apply(self: T, f, align_keys=None, **kwargs) -> T:
         if f == "where":
             align_copy = True
 
-        aligned_args = {
-            k: kwargs[k]
-            for k in align_keys
-            if isinstance(kwargs[k], (ABCSeries, ABCDataFrame))
-        }
+        aligned_args = {k: kwargs[k] for k in align_keys}
 
         for b in self.blocks:
 
@@ -402,8 +398,14 @@ def apply(self: T, f, align_keys=None, **kwargs) -> T:
                 b_items = self.items[b.mgr_locs.indexer]
 
                 for k, obj in aligned_args.items():
-                    axis = obj._info_axis_number
-                    kwargs[k] = obj.reindex(b_items, axis=axis, copy=align_copy)._values
+                    if isinstance(obj, (ABCSeries, ABCDataFrame)):
+                        axis = obj._info_axis_number
+                        kwargs[k] = obj.reindex(
+                            b_items, axis=axis, copy=align_copy
+                        )._values
+                    else:
+                        # otherwise we have an ndarray
+                        kwargs[k] = obj[b.mgr_locs.indexer]
 
             if callable(f):
                 applied = b.apply(f, **kwargs)
diff --git a/pandas/core/ops/__init__.py b/pandas/core/ops/__init__.py
index c14c4a311d66c..9a7c9fdadf90d 100644
--- a/pandas/core/ops/__init__.py
+++ b/pandas/core/ops/__init__.py
@@ -510,11 +510,13 @@ def _combine_series_frame(left, right, func, axis: int, str_rep: str):
     if axis == 0:
         values = right._values
         if isinstance(values, np.ndarray):
+            # TODO(EA2D): no need to special-case with 2D EAs
             # We can operate block-wise
             values = values.reshape(-1, 1)
+            values = np.broadcast_to(values, left.shape)
 
             array_op = get_array_op(func, str_rep=str_rep)
-            bm = left._mgr.apply(array_op, right=values.T)
+            bm = left._mgr.apply(array_op, right=values.T, align_keys=["right"])
             return type(left)(bm)
 
         new_data = dispatch_to_series(left, right, func)
diff --git a/pandas/core/ops/array_ops.py b/pandas/core/ops/array_ops.py
index 5dd7af454cbd1..a1d853e38e757 100644
--- a/pandas/core/ops/array_ops.py
+++ b/pandas/core/ops/array_ops.py
@@ -75,14 +75,7 @@ def masked_arith_op(x: np.ndarray, y, op):
         result = np.empty(x.size, dtype=dtype)
 
         if len(x) != len(y):
-            if not _can_broadcast(x, y):
-                raise ValueError(x.shape, y.shape)
-
-            # Call notna on pre-broadcasted y for performance
-            ymask = notna(y)
-            y = np.broadcast_to(y, x.shape)
-            ymask = np.broadcast_to(ymask, x.shape)
-
+            raise ValueError(x.shape, y.shape)
         else:
             ymask = notna(y)
 
@@ -211,51 +204,6 @@ def arithmetic_op(left: ArrayLike, right: Any, op, str_rep: str):
     return res_values
 
 
-def _broadcast_comparison_op(lvalues, rvalues, op) -> np.ndarray:
-    """
-    Broadcast a comparison operation between two 2D arrays.
-
-    Parameters
-    ----------
-    lvalues : np.ndarray or ExtensionArray
-    rvalues : np.ndarray or ExtensionArray
-
-    Returns
-    -------
-    np.ndarray[bool]
-    """
-    if isinstance(rvalues, np.ndarray):
-        rvalues = np.broadcast_to(rvalues, lvalues.shape)
-        result = comparison_op(lvalues, rvalues, op)
-    else:
-        result = np.empty(lvalues.shape, dtype=bool)
-        for i in range(len(lvalues)):
-            result[i, :] = comparison_op(lvalues[i], rvalues[:, 0], op)
-    return result
-
-
-def _can_broadcast(lvalues, rvalues) -> bool:
-    """
-    Check if we can broadcast rvalues to match the shape of lvalues.
-
-    Parameters
-    ----------
-    lvalues : np.ndarray or ExtensionArray
-    rvalues : np.ndarray or ExtensionArray
-
-    Returns
-    -------
-    bool
-    """
-    # We assume that lengths dont match
-    if lvalues.ndim == rvalues.ndim == 2:
-        # See if we can broadcast unambiguously
-        if lvalues.shape[1] == rvalues.shape[-1]:
-            if rvalues.shape[0] == 1:
-                return True
-    return False
-
-
 def comparison_op(
     left: ArrayLike, right: Any, op, str_rep: Optional[str] = None,
 ) -> ArrayLike:
@@ -287,8 +235,6 @@ def comparison_op(
         #  We are not catching all listlikes here (e.g. frozenset, tuple)
         #  The ambiguous case is object-dtype.  See GH#27803
         if len(lvalues) != len(rvalues):
-            if _can_broadcast(lvalues, rvalues):
-                return _broadcast_comparison_op(lvalues, rvalues, op)
             raise ValueError(
                 "Lengths must match to compare", lvalues.shape, rvalues.shape
             )