Don't create unused impact mapping in destroy_handler

Author: ricardoV94

pytensor/graph/destroyhandler.py

@@ -177,7 +177,7 @@ def _contains_cycle(fgraph, orderings):
 
 def _build_droot_impact(destroy_handler):
     droot = {}  # destroyed view + nonview variables -> foundation
-    impact = {}  # destroyed nonview variable -> it + all views of it
+    # impact = {}  # destroyed nonview variable -> it + all views of it
     root_destroyer = {}  # root -> destroyer apply
 
     for app in destroy_handler.destroyers:
@@ -202,24 +202,26 @@ def _build_droot_impact(destroy_handler):
 
             # The code here add all the variables that are views of r into
             # an OrderedSet input_impact
-            input_impact = OrderedSet()
+            # input_impact = OrderedSet()
 
             q = deque()
             q.append(input_root)
+            view_o = destroy_handler.view_o
             while len(q) > 0:
                 v = q.popleft()
-                for n in destroy_handler.view_o.get(v, []):
-                    input_impact.add(n)
+                for n in view_o.get(v, []):
+                    droot[n] = input_root
+                    # input_impact.add(n)
                     q.append(n)
 
-            for v in input_impact:
-                assert v not in droot
-                droot[v] = input_root
+            # for v in input_impact:
+            #     assert v not in droot
+            #     droot[v] = input_root
 
-            impact[input_root] = input_impact
-            impact[input_root].add(input_root)
+            # impact[input_root] = input_impact
+            # impact[input_root].add(input_root)
 
-    return droot, impact, root_destroyer
+    return droot, root_destroyer
 
 
 def inplace_candidates(fgraph, inputs, protected_inputs=None):
@@ -336,15 +338,10 @@ def __init__(self, do_imports_on_attach=True, algo=None):
         self.droot = {}
 
         """
-        Maps a variable to all variables that are indirect or direct views of it
+        Maps a "foundation" destroyed variable to all variables that are indirect or direct views of it
         (including itself) essentially the inverse of droot.
-        TODO: do all variables appear in this dict, or only those that are
-              foundations?
-        TODO: do only destroyed variables go in here? one old docstring said so.
-        TODO: rename to x_to_views after reverse engineering what x is
-
         """
-        self.impact = {}
+        # self.impact = {}
 
         """
         If a var is destroyed, then this dict will map
@@ -454,9 +451,9 @@ def refresh_droot_impact(self):
 
         """
         if self.stale_droot:
-            self.droot, self.impact, self.root_destroyer = _build_droot_impact(self)
+            self.droot, self.root_destroyer = _build_droot_impact(self)
             self.stale_droot = False
-        return self.droot, self.impact, self.root_destroyer
+        return self.droot, self.root_destroyer
 
     def on_detach(self, fgraph):
         if fgraph is not self.fgraph: