Better implementation

theano/tensor/opt.py

@@ -1180,7 +1180,7 @@ class ShapeFeature(object):
         same shape.
 
         dim_x and dim_y are optional. If used, they should be an index
-        to compare only 1 shape of x or y.
+        to compare only 1 dimension of x and y.
 
         """
         sx = self.shape_of[x]
@@ -1193,6 +1193,9 @@ class ShapeFeature(object):
             sy = [sy[dim_y]]
         assert len(sx) == len(sy)
 
+        # We look on each dimensions we want to compare.
+        # If any of them can't be asserted to be equal, return False.
+        # Otherwise, we return True at the end.
         for dx, dy in zip(sx, sy):
             if dx is dy:
                 continue
@@ -1210,12 +1213,14 @@ class ShapeFeature(object):
                 return False
             # FB I'm not sure is this handle correctly constants.
             if dx.owner.inputs[0] == dy.owner.inputs[0]:
-                return True
+                continue
             # To be sure to cover all case, call equal_computation.
             # Can't use theano.gof.graph.is_same_graph(dx, dy)
             # As it currently expect that dx and dy aren't in a FunctionGraph
             from theano.scan_module.scan_utils import equal_computations
-            return equal_computations([dx], [dy])
+            if not equal_computations([dx], [dy]):
+                return False
+        return True
 
 
 class ShapeOptimizer(Optimizer):