BatchedDot: fix comments and remove assertion

theano/tensor/basic.py

@@ -3425,29 +3425,26 @@ class BatchedDot(Op):
         gz, = grads
         xdim, ydim, gdim = x.type.ndim, y.type.ndim, gz.type.ndim
 
-        # grad is a batch of scalars, so x is a batch of vectors and y is a batch of vectors
+        # grad is a vector, so x is a matrix and y is a matrix
         if gdim == 1:
             xgrad = gz.dimshuffle(0, 'x') * y
             ygrad = gz.dimshuffle(0, 'x') * x
 
-        # x is a batch of vectors, y is a batch of matrices, grad is a batch of vectors
+        # x is a matrix, y is a tensor3, grad is a matrix
         elif xdim == 2 and ydim == 3:
             xgrad = batched_dot(gz, y.dimshuffle(0, 2, 1))
             ygrad = x.dimshuffle(0, 1, 'x') * gz.dimshuffle(0, 'x', 1)
 
-        # x is a batch of matrices, y is a batch of vectors, grad is a batch of vectors
+        # x is a tensor3, y is a matrix, grad is a matrix
         elif xdim == 3 and ydim == 2:
             xgrad = gz.dimshuffle(0, 1, 'x') * y.dimshuffle(0, 'x', 1)
             ygrad = batched_dot(x.dimshuffle(0, 2, 1), gz)
 
-        # x is a batch of matrices, y is a batch of matrices, grad is a batch of matrices
+        # x is a tensor3, y is a tensor3, grad is a tensor3
         elif xdim == ydim == 3:
             xgrad = batched_dot(gz, y.dimshuffle(0, 2, 1))
             ygrad = batched_dot(x.dimshuffle(0, 2, 1), gz)
 
-        else:
-            assert False
-
         # If x or y contain broadcastable dimensions but only one of
         # them know that a matching dimensions is broadcastable, the
         # above code don't always return the right broadcast pattern.