为了使`OpKernel`的计算过程书写更加简单，并且CPU、CUDA的代码可以复用，我们通常借助 Eigen unsupported Tensor模块来实现`Compute`接口。关于在PaddlePaddle中如何使用Eigen库，请参考[使用文档](https://github.com/PaddlePaddle/FluidDoc/blob/develop/doc/fluid/dev/use_eigen_cn.md)。
为了使`OpKernel`的计算过程书写更加简单，并且CPU、CUDA的代码可以复用，我们通常借助 Eigen unsupported Tensor模块来实现`Compute`接口。关于在PaddlePaddle中如何使用Eigen库，请参考[使用文档](https://github.com/PaddlePaddle/FluidDoc/blob/release/1.2/doc/fluid/dev/use_eigen_cn.md)。
The constructor utilizes `AddInput` to add input parameter, `AddOutput` to add output parameter, and `AddComment` to add comments for the Op, so that the corresponding information will be added to `OpProto`.
The code above adds two inputs `X` and `Y` to `MulOp`, an output `Out`, and their corresponding descriptions. Names are given in accordance to Paddle's [naming convention](https://github.com/PaddlePaddle/FluidDoc/blob/develop/doc/fluid/dev/name_convention.md).
The code above adds two inputs `X` and `Y` to `MulOp`, an output `Out`, and their corresponding descriptions. Names are given in accordance to Paddle's [naming convention](https://github.com/PaddlePaddle/FluidDoc/blob/release/1.2/doc/fluid/dev/name_convention.md).
An additional example [`ScaleOp`](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/fluid/operators/scale_op.cc#L38-L55) is implemented as follows:
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@@ -134,7 +134,7 @@ Note `AddAttr<AttrType>("scale", "...").SetDefault(1.0);` adds `scale`constant a
<aname="Defining the GradProtoMaker class"></a>
### Defining the GradProtoMaker class
Each Op must have a corresponding GraProtoMaker. If GradProtoMaker corresponding to the forward Op is not customized, Fluid provides DefaultGradProtoMaker. The default registration will use all input and output, including Input, Output, Output@Grad and so on. Using unnecessary variables will cause waste of memory.
Each Op must have a corresponding GradProtoMaker. If GradProtoMaker corresponding to the forward Op is not customized, Fluid provides DefaultGradProtoMaker. The default registration will use all input and output, including Input, Output, Output@Grad and so on. Using unnecessary variables will cause waste of memory.
The following example defines ScaleOp's GradProtoMaker.
```cpp
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@@ -244,7 +244,7 @@ Note that **different devices (CPU, CUDA)share one Op definition; whether or not
`MulOp`'s CPU and CUDA share the same `Kernel`. A non-sharing `OpKernel` example can be seen in [`OnehotCrossEntropyOpKernel`](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/fluid/operators/cross_entropy_op.cc).
To ease the writing of `OpKernel` compute, and for reusing code cross-device, [`Eigen-unsupported Tensor`](https://bitbucket.org/eigen/eigen/src/default/unsupported/Eigen/CXX11/src/Tensor/README.md?fileviewer=file-view-default) module is used to implement `Compute` interface. To learn about how the Eigen library is used in PaddlePaddle, please see [usage document](https://github.com/PaddlePaddle/FluidDoc/blob/develop/doc/fluid/dev/use_eigen_en.md).
To ease the writing of `OpKernel` compute, and for reusing code cross-device, [`Eigen-unsupported Tensor`](https://bitbucket.org/eigen/eigen/src/default/unsupported/Eigen/CXX11/src/Tensor/README.md?fileviewer=file-view-default) module is used to implement `Compute` interface. To learn about how the Eigen library is used in PaddlePaddle, please see [usage document](https://github.com/PaddlePaddle/FluidDoc/blob/release/1.2/doc/fluid/dev/use_eigen_cn.md).
This concludes the forward implementation of an operator. Next its operation and kernel need to be registered in a `.cc` file.
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@@ -460,7 +460,7 @@ If it is not necessary or concise description is enough to clearly express the a
2.Using developer-defined variable abbreviations in error messages is not easy to understand.
Example of the problem:
Example of the problem:
```
PADDLE_ENFORCE(forward_pd != nullptr,
"Fail to find eltwise_fwd_pd in device context"); //eltwise_fwd_pduser may not be understood
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@@ -481,7 +481,7 @@ If it is not necessary or concise description is enough to clearly express the a
<aname="Special instructions for OP InferShape check message"></a>
#### Special Instructions for OP InferShape Check Message
#### Special Instructions for OP InferShape Check Message
- Check input and output variables, please follow the following format
`Input(variable name) of OP name operator should not be null.`
