Allow broadcasting in specialized numba dispatch of AdvancedIncSubtensor

pytensor/link/numba/dispatch/subtensor.py

@@ -130,15 +130,6 @@
         if isinstance(idx.type, TensorType)
     ]
 
-    def broadcasted_to(x_bcast: tuple[bool, ...], to_bcast: tuple[bool, ...]):
-        # Check that x is not broadcasted to y based on broadcastable info
-        if len(x_bcast) < len(to_bcast):
-            return True
-        for x_bcast_dim, to_bcast_dim in zip(x_bcast, to_bcast, strict=True):
-            if x_bcast_dim and not to_bcast_dim:
-                return True
-        return False
-
     # Special implementation for consecutive integer vector indices
     if (
         not basic_idxs
@@ -151,17 +142,6 @@
         )
         # Must be consecutive
         and not op.non_consecutive_adv_indexing(node)
-        # y in set/inc_subtensor cannot be broadcasted
-        and (
-            y is None
-            or not broadcasted_to(
-                y.type.broadcastable,
-                (
-                    x.type.broadcastable[: adv_idxs[0]["axis"]]
-                    + x.type.broadcastable[adv_idxs[-1]["axis"] :]
-                ),
-            )
-        )
     ):
         return numba_funcify_multiple_integer_vector_indexing(op, node, **kwargs)
 
@@ -191,14 +171,24 @@
     return numba_funcify_default_subtensor(op, node, **kwargs)
 
 
+def _broadcasted_to(x_bcast: tuple[bool, ...], to_bcast: tuple[bool, ...]):
+    # Check that x is not broadcasted to y based on broadcastable info
+    if len(x_bcast) < len(to_bcast):
+        return True
+    for x_bcast_dim, to_bcast_dim in zip(x_bcast, to_bcast, strict=True):
+        if x_bcast_dim and not to_bcast_dim:
+            return True
+    return False
+
+
 def numba_funcify_multiple_integer_vector_indexing(
     op: AdvancedSubtensor | AdvancedIncSubtensor, node, **kwargs
 ):
     # Special-case implementation for multiple consecutive vector integer indices (and set/incsubtensor)
     if isinstance(op, AdvancedSubtensor):
-        y, idxs = None, node.inputs[1:]
+        idxs = node.inputs[1:]
     else:
-        y, *idxs = node.inputs[1:]
+        idxs = node.inputs[2:]
 
     first_axis = next(
         i for i, idx in enumerate(idxs) if isinstance(idx.type, TensorType)
@@ -211,6 +201,10 @@
         )
     except StopIteration:
         after_last_axis = len(idxs)
+    last_axis = after_last_axis - 1
+
+    vector_indices = idxs[first_axis:after_last_axis]
+    assert all(v.type.broadcastable == (False,) for v in vector_indices)
 
     if isinstance(op, AdvancedSubtensor):
 
@@ -231,43 +225,59 @@
 
         return advanced_subtensor_multiple_vector
 
-    elif op.set_instead_of_inc:
+    else:
         inplace = op.inplace
 
-        @numba_njit
-        def advanced_set_subtensor_multiple_vector(x, y, *idxs):
-            vec_idxs = idxs[first_axis:after_last_axis]
-            x_shape = x.shape
+        # Check if y must be broadcasted
+        # Includes the last integer vector index,
+        x, y = node.inputs[:2]
+        indexed_bcast_dims = (
+            *x.type.broadcastable[:first_axis],
+            *x.type.broadcastable[last_axis:],
+        )
+        y_is_broadcasted = _broadcasted_to(y.type.broadcastable, indexed_bcast_dims)
 
-            if inplace:
-                out = x
-            else:
-                out = x.copy()
+        if op.set_instead_of_inc:
 
-            for outer in np.ndindex(x_shape[:first_axis]):
-                for i, scalar_idxs in enumerate(zip(*vec_idxs)):  # noqa: B905
-                    out[(*outer, *scalar_idxs)] = y[(*outer, i)]
-            return out
+            @numba_njit
+            def advanced_set_subtensor_multiple_vector(x, y, *idxs):
+                vec_idxs = idxs[first_axis:after_last_axis]
+                x_shape = x.shape
 
-        return advanced_set_subtensor_multiple_vector
+                if inplace:
+                    out = x
+                else:
+                    out = x.copy()
 
-    else:
-        inplace = op.inplace
+                if y_is_broadcasted:
+                    y = np.broadcast_to(y, x_shape[:first_axis] + x_shape[last_axis:])
 
-        @numba_njit
-        def advanced_inc_subtensor_multiple_vector(x, y, *idxs):
-            vec_idxs = idxs[first_axis:after_last_axis]
-            x_shape = x.shape
+                for outer in np.ndindex(x_shape[:first_axis]):
+                    for i, scalar_idxs in enumerate(zip(*vec_idxs)):  # noqa: B905
+                        out[(*outer, *scalar_idxs)] = y[(*outer, i)]
+                return out
+
+            return advanced_set_subtensor_multiple_vector
+
+        else:
+
+            @numba_njit
+            def advanced_inc_subtensor_multiple_vector(x, y, *idxs):
+                vec_idxs = idxs[first_axis:after_last_axis]
+                x_shape = x.shape
+
+                if inplace:
+                    out = x
+                else:
+                    out = x.copy()
 
-            if inplace:
-                out = x
-            else:
-                out = x.copy()
+                if y_is_broadcasted:
+                    y = np.broadcast_to(y, x_shape[:first_axis] + x_shape[last_axis:])
 
-            for outer in np.ndindex(x_shape[:first_axis]):
-                for i, scalar_idxs in enumerate(zip(*vec_idxs)):  # noqa: B905
-                    out[(*outer, *scalar_idxs)] += y[(*outer, i)]
-            return out
+                for outer in np.ndindex(x_shape[:first_axis]):
+                    for i, scalar_idxs in enumerate(zip(*vec_idxs)):  # noqa: B905
+                        out[(*outer, *scalar_idxs)] += y[(*outer, i)]
+                return out
 
         return advanced_inc_subtensor_multiple_vector
 

tests/link/numba/test_subtensor.py

@@ -392,8 +392,8 @@ def test_AdvancedIncSubtensor1(x, y, indices):
             np.array(-99),  # Broadcasted value
             ([1, 2], [2, 3]),  # 2 vector indices
             False,
-            True,
-            True,
+            False,
+            False,
         ),
         (
             np.arange(3 * 4 * 5).reshape((3, 4, 5)),