sketch of grad for max

tensor.py

@@ -519,6 +519,10 @@ class MaxAndArgmax(Op):
     def perform(self, node, (x, axis), (max, max_idx)):
         max[0] = numpy.max(x, axis)
         max_idx[0] = numpy.argmax(x, axis)
+#     def grad(self, (x, axis), (g_max, g_max_idx)):
+#         # This only works if axis is 0, else the max is broadcasted wrong in the call to eq
+#         g_x = eq(max(x, axis), x) * g_max
+#         return g_x, None
 max_and_argmax = MaxAndArgmax()