Fix bug of gradient interface

python/paddle/fluid/framework.py

@@ -408,7 +408,8 @@ class Variable(object):
         self._ivar._run_backward()
 
     def _gradient(self):
-        return np.array(self._ivar._grad_value())
+        new_ivar = self._ivar._grad_ivar._copy_to(core.CPUPlace(), True)
+        return np.array(new_ivar.value().get_tensor())
 
     def _clear_gradient(self):
         self._ivar._clear_gradient()