Instructions on contributing to C++ gradients.

Change: 147892613

1 files changed, 52 insertions, 0 deletions

diff --git a/tensorflow/cc/gradients/README.md b/tensorflow/cc/gradients/README.md
new file mode 100644
index 0000000000..3253163cc7
--- /dev/null
+++ b/tensorflow/cc/gradients/README.md
@@ -0,0 +1,52 @@
+# C++ gradients
+
+Gradients are currently being ported from
+[python](https://github.com/tensorflow/tensorflow/tree/master/tensorflow/python/ops)
+to C++ (in this directory).
+
+Contributions are welcome and much appreciated; please follow the instructions
+below.
+
+1.  Create the op gradient function in `foo_grad.cc` corresponding to the
+    `foo_grad.py` file where the op originated (i.e. `array_grad.py` op
+    gradients should be written in `array_grad.cc`).
+
+2.  Write the op gradient with the following naming scheme:
+
+        Status OpNameGrad(const Scope& scope, const Operation& op,
+                          const std::vector<Output>& grad_inputs,
+                          std::vector<Output>* grad_outputs) {
+          ...
+          return scope.status();
+        }
+        REGISTER_GRADIENT_OP("OpName", OpNameGrad);
+
+3.  Ops gradients are implemented by using the [C++
+    API](https://www.tensorflow.org/api_docs/cc/).
+
+4.  Tests should be included in `foo_grad_test.cc`. Please see
+    [`array_grad_test.cc`](https://github.com/tensorflow/tensorflow/blob/master/tensorflow/cc/gradients/array_grad_test.cc)
+    for an many examples. Tests are as simple as, creating a placeholder input
+    for the op's inputs and calling `RunTest` (`RunTest` uses a [gradient
+    checker](https://github.com/tensorflow/tensorflow/blob/master/tensorflow/cc/framework/gradient_checker.cc)
+    to verify that the theoretical gradient matches the numeric gradient). For
+    example:
+
+        TEST_F(ArrayGradTest, IdentityGrad) {
+          TensorShape shape({5, 2});
+          auto x = Placeholder(scope_, DT_FLOAT, Placeholder::Shape(shape));
+          auto y = Identity(scope_, x);
+          RunTest(x, shape, y, shape);
+        }
+
+NOTE: There are some ops that require features from the C++ API that are not yet
+implemented.
+
+*   Ops that require PartialTensorShape information cannot yet be implemented.
+
+*   Ops that require SparseTensor or IndexSlices (currently only in python)
+    cannot yet be implemented.
+
+*   Maybe more.
+
+For questions: Please create an issue assigned to suharshs.