Merge pull request #204 from nouiz/rop_doc

doc/cifarSC2011/extending_theano.txt

@@ -133,6 +133,15 @@ Op example
         def grad(self, inputs, output_grads):
             return [output_grads[0] * 2]
 
+	def R_op(self, inputs, eval_points):
+            # R_op can receive None as eval_points.
+            # That mean there is no diferientiable path through that input
+            # If this imply that you cannot compute some outputs,
+            # return None for those.
+            if eval_points[0] is None:
+                return eval_points
+            return self.grad(inputs, eval_points)
+
 Test it!
 
 .. code-block:: python
@@ -165,6 +174,34 @@ To verify the grad method of the DoubleOp, you can use this:
 If nothing happens, then it works! If you want to see it fail, you can
 implement a wrong gradient (for instance removing the multiplication by 2).
 
+Testing the Rop
+---------------
+
+The functions :func:`RopLop_checker.check_mat_rop_lop`,
+:func:`RopLop_checker.check_rop_lop` and :func:`RopLop_checker.check_nondiff_rop` allow to test the implemntation of the Rop of one function.
+
+To verify the Rop method of the DoubleOp, you can use this:
+
+.. code-block:: python
+
+   import numpy
+   import theano.tests
+   from theano.tensor.tests.test_rop import RopLop_checker
+   class test_Double(RopLop_checker):
+       def setUp(self):
+           super(test_Double, self).setUp()
+       def test_double_rop(self):
+           self.check_rop_lop(DoubleOp()(self.x), self.in_shape)
+	   assert False
+
+You can use `nosetests` to run it as all other test in Theano or you can run it like that in a python shell:
+
+.. code-block:: python
+
+   t = test_Double("test_double_rop")
+   t.setUp()
+   t.test_double_rop()
+
 Exercises 8
 -----------