Merge pull request #5634 from bordesf/master

theano/tensor/nnet/nnet.py

@@ -14,13 +14,14 @@ revisited later when all the intermediate part are on the GPU.
 """
 from __future__ import absolute_import, print_function, division
 import logging
+import warnings
 import numpy
 from six.moves import xrange
 
 import theano
 from theano import gof
 from theano import scalar
-from theano.tensor import extra_ops
+from theano.tensor import extra_ops, as_tensor_variable
 from theano.gof.opt import copy_stack_trace
 from theano.tensor import basic as tensor, subtensor, opt, elemwise
 from theano.tensor.type import (values_eq_approx_remove_inf,
@@ -802,6 +803,9 @@ def softmax_graph(c):
 
 
 def softmax(c):
+    c = as_tensor_variable(c)
+    if c.broadcastable[-1]:
+        warnings.warn("The softmax is applied on a dimension of shape 1, which does not have a semantic meaning.")
     return softmax_op(c)