Do not set rng updates for RandomVariables that are not computed in the graph

Author: ricardoV94

pymc/aesaraf.py

@@ -39,9 +39,9 @@
     Apply,
     Constant,
     Variable,
-    ancestors,
     clone_get_equiv,
     graph_inputs,
+    vars_between,
     walk,
 )
 from aesara.graph.fg import FunctionGraph
@@ -975,8 +975,8 @@ def compile_pymc(
     output_to_list = outputs if isinstance(outputs, (list, tuple)) else [outputs]
     for rv in (
         node
-        for node in ancestors(output_to_list)
-        if node.owner and isinstance(node.owner.op, RandomVariable)
+        for node in vars_between(inputs, output_to_list)
+        if node.owner and isinstance(node.owner.op, RandomVariable) and node not in inputs
     ):
         rng = rv.owner.inputs[0]
         if not hasattr(rng, "default_update"):

pymc/tests/test_aesaraf.py

@@ -636,3 +636,29 @@ def test_compile_pymc_missing_default_explicit_updates():
     # And again, it should be overridden by an explicit update
     f = compile_pymc([], x, updates={rng: x.owner.outputs[0]})
     assert f() != f()
+
+
+def test_compile_pymc_updates_inputs():
+    """Test that compile_pymc does not include rngs updates of variables that are inputs
+    or ancestors to inputs
+    """
+    x = at.random.normal()
+    y = at.random.normal(x)
+    z = at.random.normal(y)
+
+    for inputs, rvs_in_graph in (
+        ([], 3),
+        ([x], 2),
+        ([y], 1),
+        ([z], 0),
+        ([x, y], 1),
+        ([x, y, z], 0),
+    ):
+        fn = compile_pymc(inputs, z, on_unused_input="ignore")
+        fn_fgraph = fn.maker.fgraph
+        # Each RV adds a shared input for its rng
+        assert len(fn_fgraph.inputs) == len(inputs) + rvs_in_graph
+        # If the output is an input, the graph has a DeepCopyOp
+        assert len(fn_fgraph.apply_nodes) == max(rvs_in_graph, 1)
+        # Each RV adds a shared output for its rng
+        assert len(fn_fgraph.outputs) == 1 + rvs_in_graph