Fix _delta on non rightmost axes

Author: ricardoV94

pytensor/tensor/einsum.py

@@ -17,6 +17,7 @@
 from pytensor.tensor.basic import (
     arange,
     as_tensor,
+    expand_dims,
     get_vector_length,
     moveaxis,
     stack,
@@ -176,7 +177,8 @@ def _delta(shape: TensorVariable, axes: Sequence[int]) -> TensorVariable:
     iotas = [_iota(base_shape, i) for i in range(len(axes))]
     eyes = [eq(i1, i2) for i1, i2 in pairwise(iotas)]
     result = reduce(and_, eyes)
-    return broadcast_to(result, shape)
+    non_axes = [i for i in range(len(tuple(shape))) if i not in axes]
+    return broadcast_to(expand_dims(result, non_axes), shape)
 
 
 def _general_dot(

tests/tensor/test_einsum.py

@@ -67,6 +67,11 @@ def test_delta():
         [[1.0, 0.0], [0.0, 1.0]],
     )
 
+    np.testing.assert_allclose(
+        _delta((2, 2, 2), (0, 1)).eval(mode=mode),
+        [[[1, 1], [0, 0]], [[0, 0], [1, 1]]],
+    )
+
 
 def test_general_dot():
     rng = np.random.default_rng(45)