Update threshold for float16.

theano/tensor/nnet/sigm.py

@@ -68,8 +68,9 @@ class ScalarSigmoid(scalar.UnaryScalarOp):
         #                   (theano._asarray(1.0, dtype=dt) +
         #                    numpy.exp(-theano._asarray([i,-i], dtype=dt))))
 
-        if (node.inputs[0].type == scalar.float32 or
-                node.inputs[0].type == scalar.float16):
+        if node.inputs[0].type == scalar.float16:
+            return """%(z)s = %(x)s < -11.0f ? 0.0 : %(x)s > 7.0f ? 1.0f : 1.0f /(1.0f + exp(-%(x)s));""" % locals()
+        elif node.inputs[0].type == scalar.float32:
             return """%(z)s = %(x)s < -88.0f ? 0.0 : %(x)s > 15.0f ? 1.0f : 1.0f /(1.0f + exp(-%(x)s));""" % locals()
         elif node.inputs[0].type == scalar.float64:
             return """%(z)s = %(x)s < -709.0 ? 0.0 : %(x)s > 19.0 ? 1.0 : 1.0 /(1.0+exp(-%(x)s));""" % locals()