Clarified docstring and removed unnecessary subtensor.

theano/tensor/opt.py

@@ -2181,7 +2181,7 @@ def local_subtensor_of_alloc(node):
 @gof.local_optimizer([Subtensor])
 def local_subtensor_of_dot(node):
     """
-    T.dot(A,B)[i] -> T.dot(A[i],B)
+    This optimization translates T.dot(A, B)[xs+ys] into T.dot(A[xs,:], B[:,ys]).
 
     """
     if not isinstance(node.op, Subtensor):
@@ -2193,6 +2193,7 @@ def local_subtensor_of_dot(node):
     # We don't want to compute twice the sub part.
     if len(node.inputs[0].clients) > 1:
         return
+
     a = node.inputs[0].owner.inputs[0]
     b = node.inputs[0].owner.inputs[1]
 
@@ -2209,7 +2210,7 @@ def local_subtensor_of_dot(node):
     import pdb; pdb.set_trace()
 
     a_sub = Subtensor(a_indices).make_node(a, *a_inputs)
-    b_sub = Subtensor(b_indices).make_node(b, *b_inputs)
+    b_sub = b if len(b_indices) == 1 else Subtensor(b_indices).make_node(b, *b_inputs)
 
     return [T.dot(a_sub, b_sub)]