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