Stop some unnecessary Constant cloning

aesara/graph/basic.py

@@ -603,15 +603,8 @@ class Constant(Variable):
             return f"{type(self).__name__}{{{name}}}"
 
     def clone(self):
-        """Create a shallow clone.
-
-        We clone this object, but we don't clone the data to lower memory
-        requirement. We suppose that the data will never change.
-
-        """
-        cp = self.__class__(self.type, self.data, self.name)
-        cp.tag = copy(self.tag)
-        return cp
+        """Return `self`, because there's no reason to clone a constant."""
+        return self
 
     def __set_owner(self, value):
         """Prevent the :prop:`owner` property from being set.

aesara/scan/utils.py

@@ -61,7 +61,7 @@ def safe_new(
             nwx.tag = copy.copy(x.tag)
             return nwx
         else:
-            return x.clone()
+            return x
     # Note, `as_tensor_variable` will convert the `Scalar` into a
     # `TensorScalar` that will require a `ScalarFromTensor` `Op`, making the
     # push-out optimization fail
@@ -697,14 +697,8 @@ def reconstruct_graph(inputs, outputs, tag=None):
     if tag is None:
         tag = ""
     nw_inputs = [safe_new(x, tag) for x in inputs]
-    givens = OrderedDict()
-    for nw_x, x in zip(nw_inputs, inputs):
-        givens[x] = nw_x
-    allinputs = list(graph_inputs(outputs))
-    for inp in allinputs:
-        if isinstance(inp, Constant):
-            givens[inp] = inp.clone()
 
+    givens = {x: nw_x for nw_x, x in zip(nw_inputs, inputs)}
     nw_outputs = clone_replace(outputs, replace=givens)
     return (nw_inputs, nw_outputs)
 

tests/graph/test_basic.py

@@ -200,13 +200,13 @@ class TestClone(X):
         c1 = at.constant(1.5)
 
         i, o = clone([c1], [c1])
-        assert i[0] is not c1 and o[0] is not c1
+        assert i[0] is c1 and o[0] is c1
 
         i, o = clone([c1], [c1], False)
         assert i[0] is c1 and o[0] is c1
 
         i, o = clone([c1], [c1], True, False)
-        assert i[0] is not c1 and o[0] is not c1
+        assert i[0] is c1 and o[0] is c1
 
         i, o = clone([c1], [c1], False, True)
         assert i[0] is c1 and o[0] is c1