fixed ticket #326

theano/compile/debugmode.py

@@ -207,7 +207,7 @@ def _optcheck_env(input_specs, output_specs, accept_inplace = False):
     env.extend(Supervisor(input for spec, input in zip(input_specs, inputs) if not (spec.mutable or (hasattr(env, 'destroyers') and env.destroyers(input)))))
     return env, map(SymbolicOutput, updates), equivalence_tracker
 
-def _check_inputs(node, storage_map, r_vals, dr_vals, active_nodes):
+def _check_inputs(node, storage_map, r_vals, dr_vals, active_nodes, clobber_dr_vals=True):
     """Raise BadDestroyMap if necessary, update dr_vals"""
     destroyed_idx_list = []
     destroy_map = getattr(node.op, 'destroy_map', {})
@@ -225,7 +225,9 @@ def _check_inputs(node, storage_map, r_vals, dr_vals, active_nodes):
                     if dr_vals.get(r, (0, node))[1] is not node:
                         # bad: there should only be one active node that destroys any result
                         raise Exception('failure in topological ordering')
+                    if clobber_dr_vals:
                         dr_vals[r] = (storage_map[r][0], node) #no copy, this is the last use of this variable
+                    storage_map[r][0] = None #make sure that dr_vals[r] doens't get used again
             else:
                 raise BadDestroyMap(node, r_idx, r_vals[r], storage_map[r][0])
 
@@ -572,10 +574,10 @@ class _Linker(gof.link.LocalLinker):
                 thunk.inputs = node_input_storage
                 thunk.outputs = node_output_storage
                 thunks_c.append(thunk)
+
             except (NotImplementedError, utils.AbstractFunctionError):
                 thunks_c.append(None)
 
-
             p = node.op.perform
             thunk = (lambda p = p, i = node_input_storage, o = node_output_storage, n =
                     node: p(n, [x[0] for x in i], o))
@@ -640,7 +642,8 @@ class _Linker(gof.link.LocalLinker):
 
                     thunk_py()
 
-                    _check_inputs(node, storage_map, r_vals, dr_vals, active_order_set)
+                    _check_inputs(node, storage_map, r_vals, dr_vals, active_order_set,
+                            clobber_dr_vals=True)
 
                     #retrieve each output from the storage_map
                     for r in node.outputs:
@@ -660,7 +663,8 @@ class _Linker(gof.link.LocalLinker):
 
                         thunk_c()
 
-                        _check_inputs(node, storage_map, r_vals, dr_vals, active_order_set)
+                        _check_inputs(node, storage_map, r_vals, dr_vals, active_order_set,
+                                clobber_dr_vals=False)
 
                         for r in node.outputs:
                             if not r.type.is_valid_value(storage_map[r][0]):