Added Theano flags DebugMode.warn_input_not_reused that default to True. This…

theano/compile/debugmode.py

@@ -45,6 +45,11 @@ AddConfigVar('DebugMode.check_strides',
             "On difference: (0) - ignore, (1) warn, or (2) raise error"),
         IntParam(1, lambda i: i in (0,1,2)))
 
+AddConfigVar('DebugMode.warn_input_not_reused',
+        ("Generate a warning when the destroy_map tell that an op work inplace, but the op did not reuse the input for its output."
+         ),
+        BoolParam(True))
+
 import logging
 _logger=logging.getLogger("theano.compile.debugmode")
 _logger.setLevel(logging.WARNING)
@@ -500,7 +505,7 @@ def _optcheck_env(input_specs, output_specs, accept_inplace = False):
     return env, map(SymbolicOutput, updates), equivalence_tracker
 
 def _check_inputs(node, storage_map, r_vals, dr_vals, active_nodes, clobber_dr_vals=True,
-        perform=None):
+        perform=None, warn_input_not_reused=True):
     """Raise BadDestroyMap if necessary, update dr_vals"""
     destroyed_idx_list = []
     destroy_map = getattr(node.op, 'destroy_map', {})
@@ -508,6 +513,12 @@ def _check_inputs(node, storage_map, r_vals, dr_vals, active_nodes, clobber_dr_v
         destroyed_idx_list.extend(i_pos_list)
     destroyed_res_list = [node.inputs[i] for i in destroyed_idx_list]
 
+    if warn_input_not_reused and destroyed_res_list:
+        dmap=getattr(node.op,'destroy_map',{})
+        for oo,ii in dmap.iteritems():
+            if storage_map[node.outputs[oo]][0] is not storage_map[node.inputs[ii[0]]][0]:
+                warning("input idx %d marked as destroyed was not changed for node '%s'"%(ii[0],str(node)))
+
     for r_idx, r in enumerate(node.inputs):
         if not r.type.values_eq(r_vals[r], storage_map[r][0]):
             # some input node 'r' got changed by running the node
@@ -1123,7 +1134,8 @@ class _Linker(gof.link.LocalLinker):
                             #if r in r_vals:
 
                         _check_inputs(node, storage_map, r_vals, dr_vals, active_order_set,
-                                clobber_dr_vals=True, perform='py')
+                                      clobber_dr_vals=True, perform='py',
+                                      warn_input_not_reused=config.DebugMode.warn_input_not_reused)
 
                         _check_viewmap(node, storage_map)
 
@@ -1181,7 +1193,8 @@ class _Linker(gof.link.LocalLinker):
                                     self.maker.mode.require_matching_strides, node.op)
 
                         _check_inputs(node, storage_map, r_vals, dr_vals, active_order_set,
-                                clobber_dr_vals=clobber, perform='c')
+                                      clobber_dr_vals=clobber, perform='c',
+                                      warn_input_not_reused=config.DebugMode.warn_input_not_reused)
 
                         _check_viewmap(node, storage_map)