use absolute reference for abs_

theano/tensor/tests/test_basic.py

@@ -6449,6 +6449,10 @@ class TestTensorInstanceMethods(unittest.TestCase):
         # Test equivalent advanced indexing
         assert_array_equal(X[:,indices].eval({X: x}), x[:,indices])
 
+def test_norm():
+    x = theano.tensor.vector('x')
+    x.norm(2)
+
 if __name__ == '__main__':
 
     t = TestInferShape('setUp')

theano/tensor/var.py

@@ -462,7 +462,8 @@ class _tensor_py_operators:
             raise NotImplementedError()
         # optimizations will/should catch cases like L=1, L=2
         return theano.tensor.basic.pow(
-            theano.tensor.basic.pow(abs_(self), L).sum(axis=axis), 1.0 / L)
+            theano.tensor.basic.pow(
+                theano.tensor.basic.abs_(self), L).sum(axis=axis), 1.0 / L)
 
     def mean(self, axis=None, dtype=None, keepdims=False, acc_dtype=None):
         """See `theano.tensor.mean`"""