Add unbroadcast in an opt.

theano/tensor/opt.py

@@ -2014,6 +2014,15 @@ def local_subtensor_of_alloc(node):
     rval = T.alloc(nw_val, *nw_dims)
     if type(rval) not in (list, tuple):
         rval = [rval]
+    if rval[0].type != node.outputs[0].type:
+        #It happen that the make_node() isn't able to infer that some
+        #dimensions are broadcastable, but that now we can infer
+        #that. So we need to remove that information here.
+        rval[0] = theano.tensor.unbroadcast(
+            rval[0],
+            *[i for i, (b1, b2) in enumerate(zip(rval[0].broadcastable,
+                                                node.outputs[0].broadcastable))
+             if b1 and not b2])
     return rval