Define validation function for the inner graph

theano/scan_module/scan_op.py

@@ -179,6 +179,36 @@ class Scan(PureOp):
             self._cmodule_key = gof.CLinker().cmodule_key_(local_fgraph, [])
             self._hash_inner_graph = hash(self._cmodule_key)
 
+    def validate_inner_graph(self):
+        """ Perform some elementary validations on the inner graph to ensure
+        that it is coherent.
+        """
+
+        # For every recurrent output, iterate over the associated inner
+        # inputs and output and ensure that they have the same dtype
+        nb_recurr_outputs = self.n_mit_mot + self.n_mit_sot + self.n_sit_sot
+        outer_iidx_from_outer_oidx = self.get_outer_iidx_from_outer_oidx_seq()
+
+        for outer_oidx in range(nb_recurr_outputs):
+
+            outer_iidx = outer_iidx_from_outer_oidx[outer_oidx]
+
+            inner_iidxs = self.get_inner_iidx_from_outer_iidx(outer_iidx)
+            inner_oidxs = self.get_inner_oidx_from_outer_oidx(outer_oidx)
+
+            for (inner_iidx, inner_oidx) in itertools.product(inner_iidxs,
+                                                              inner_oidxs):
+
+                type_input = self.inputs[inner_iidx].type
+                type_output = self.outputs[inner_oidx].type
+                if (type_input != type_output):
+                    raise TypeError("Inconsistency in the inner graph of "
+                                    "scan '%s' : an input and an output are "
+                                    "associated with the same recurrent state "
+                                    "and should have the same type but have "
+                                    "type '%s' and '%s' respectively." %
+                                    (self.name, type_input, type_output))
+
     def __setstate__(self, d):
         self.__dict__.update(d)
         if "allow_gc" not in self.__dict__: