Fix Sng handling of nan and fix related test

theano/scalar/basic.py

@@ -2104,7 +2104,7 @@ class Sgn(UnaryScalarOp):
         (z,) = outputs
         type = node.inputs[0].type
         if type in float_types:
-            return "%(z)s = (%(x)s >= 0) ? (%(x)s == 0) ? 0.0 : 1.0 : -1.0;" % locals()
+            return '%(z)s = (%(x)s > 0) ? 1. : ((%(x)s < 0) ? -1. : (isnan(%(x)s) ? NAN : 0.));' % locals()
         if type in int_types:
             return "%(z)s = (%(x)s >= 0) ? (%(x)s == 0) ? 0 : 1 : -1;" % locals()
         raise TypeError()  # complex has no sgn
@@ -2112,7 +2112,7 @@ class Sgn(UnaryScalarOp):
     def c_code_cache_version(self):
         s = super(Sgn, self).c_code_cache_version()
         if s:
-            return (3,) + s
+            return (4,) + s
         else:  # if parent is unversioned, we are too
             return s
 sgn = Sgn(same_out_nocomplex, name='sgn')

theano/tensor/tests/test_basic.py

@@ -4149,9 +4149,15 @@ class test_comparison(unittest.TestCase):
                 (shared(l.astype(dtype)), r, False),
                 (shared(l.astype(dtype)), constant(r), False),
             ]:
+                mode = get_default_mode()
+                mode.check_isfinite = False
                 try:
-                    fn1 = inplace_func([], isclose(x, y, equal_nan=False))
-                    fn2 = inplace_func([], isclose(x, y, equal_nan=True))
+                    o1 = isclose(x, y, equal_nan=False)
+                    fn1 = inplace_func([], o1, mode=mode)
+
+                    o2 = isclose(x, y, equal_nan=True)
+                    fn2 = inplace_func([], o2, mode=mode)
+
                     v1 = fn1()
                     v2 = fn2()
                     self.assertTrue(