Return input directly with redundant shape in specify_shape

aesara/tensor/shape.py

@@ -556,6 +556,16 @@ def specify_shape(
             except ValueError:
                 raise ValueError("Shape vector must have fixed dimensions")
 
+    # If the specified shape is already encoded in the input static shape, do nothing
+    # This ignores Aesara constants in shape
+    x = at.as_tensor_variable(x)
+    new_shape_info = any(
+        s != xts for (s, xts) in zip(shape, x.type.shape) if s is not None
+    )
+    # If shape does not match x.ndim, we rely on the `Op` to raise a ValueError
+    if not new_shape_info and len(shape) == x.type.ndim:
+        return x
+
     return _specify_shape(x, *shape)
 
 

tests/tensor/test_shape.py

@@ -498,6 +498,18 @@ class TestSpecifyShape(utt.InferShapeTester):
             SpecifyShape,
         )
 
+    def test_direct_return(self):
+        """Test that when specified shape does not provide new information, input is
+        returned directly."""
+        x = TensorType("float64", shape=(1, 2, None))("x")
+
+        assert specify_shape(x, (1, 2, None)) is x
+        assert specify_shape(x, (None, None, None)) is x
+
+        assert specify_shape(x, (1, 2, 3)) is not x
+        assert specify_shape(x, (None, None, 3)) is not x
+        assert specify_shape(x, (1, 3, None)) is not x
+
 
 class TestRopLop(RopLopChecker):
     def test_shape(self):