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  <div class="section" id="operator">
<span id="operator"></span><h1>如何写新的Operator<a class="headerlink" href="#operator" title="永久链接至标题">¶</a></h1>
<ul class="simple">
<li><a class="reference external" href="#概念简介">概念简介</a></li>
<li><a class="reference external" href="#实现c类">实现C++类</a><ul>
<li><a class="reference external" href="#定义protomaker类">定义ProtoMaker类</a></li>
<li><a class="reference external" href="#定义operator类">定义Operator类</a></li>
<li><a class="reference external" href="#定义opkernel类">定义OpKernel类</a></li>
<li><a class="reference external" href="#注册operator">注册Operator</a></li>
<li><a class="reference external" href="#编译">编译</a></li>
</ul>
</li>
<li><a class="reference external" href="#绑定python">绑定Python</a></li>
<li><a class="reference external" href="#实现单元测试">实现单元测试</a><ul>
<li><a class="reference external" href="#前向operator单测">前向Operator单测</a></li>
<li><a class="reference external" href="#反向operator单测">反向Operator单测</a></li>
<li><a class="reference external" href="#编译和执行">编译和执行</a></li>
</ul>
</li>
<li><a class="reference external" href="#注意事项">注意事项</a></li>
</ul>
<div class="section" id="">
<span id="id1"></span><h2>概念简介<a class="headerlink" href="#" title="永久链接至标题">¶</a></h2>
<p>简单介绍需要用到基类，详细介绍请参考设计文档。</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">framework::OperatorBase</span></code>: Operator(简写，Op)基类。</li>
<li><code class="docutils literal"><span class="pre">framework::OpKernel</span></code>: Op计算函数的基类，称作Kernel。</li>
<li><code class="docutils literal"><span class="pre">framework::OperatorWithKernel</span></code>：继承自OperatorBase，Op有计算函数，称作有Kernel。</li>
<li><code class="docutils literal"><span class="pre">class</span> <span class="pre">OpProtoAndCheckerMaker</span></code>：描述该Op的输入、输出、属性、注释,主要用于Python API接口生成</li>
</ul>
<p>依据是否包含kernel，可以将Op分为两种：包含Kernel的Op和不包含kernel的Op，前者Op的定义继承自<code class="docutils literal"><span class="pre">OperatorWithKernel</span></code>，后者继承自<code class="docutils literal"><span class="pre">OperatorBase</span></code>。本教程主要介绍带Kernel的Op如何写，简单总结Op需要包含的内容如下：</p>
<p>内容            | 定义位置
&#8212;&#8212;&#8212;&#8212;&#8211;  | :&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;-
OpProtoMake定义  | <code class="docutils literal"><span class="pre">.cc</span></code>文件，Backward Op不需要定义OpProtoMake
Op定义           | <code class="docutils literal"><span class="pre">.cc</span></code>文件
Kernel实现       | CPU、CUDA共享Kernel实现在<code class="docutils literal"><span class="pre">.h</span></code>文件中，否则，CPU 实现在<code class="docutils literal"><span class="pre">.cc</span></code>文件中，CUDA 实现在<code class="docutils literal"><span class="pre">.cu</span></code>文件中。
注册Op           | Op注册实现在<code class="docutils literal"><span class="pre">.cc</span></code>文件；Kernel注册CPU实现在<code class="docutils literal"><span class="pre">.cc</span></code>文件中，CUDA实现在<code class="docutils literal"><span class="pre">.cu</span></code>文件中</p>
<p>实现新的op都添加至目录<a class="reference external" href="https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/operators">paddle/operators</a>下，文件命名以<code class="docutils literal"><span class="pre">*_op.h</span></code>（如有） 、 <code class="docutils literal"><span class="pre">*_op.cc</span></code> 、<code class="docutils literal"><span class="pre">*_op.cu</span></code>（如有）结尾。<strong>系统会根据文件名自动构建op和其对应的Python扩展。</strong></p>
<p>下面以矩阵乘操作，即<a class="reference external" href="https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/operators/mul_op.cc">MulOp</a>为例来介绍如何写带Kernel的Operator。</p>
</div>
<div class="section" id="c">
<span id="c"></span><h2>实现C++类<a class="headerlink" href="#c" title="永久链接至标题">¶</a></h2>
<div class="section" id="protomaker">
<span id="protomaker"></span><h3>定义ProtoMaker类<a class="headerlink" href="#protomaker" title="永久链接至标题">¶</a></h3>
<p>矩阵乘法的公式：$Out = X * Y$, 可见该计算由两个输入，一个输出组成。</p>
<p>首先定义<code class="docutils literal"><span class="pre">ProtoMaker</span></code>来描述该Op的输入、输出，并添加注释：</p>
<div class="highlight-cpp"><div class="highlight"><pre><span></span><span class="k">class</span> <span class="nc">MulOpMaker</span> <span class="o">:</span> <span class="k">public</span> <span class="n">framework</span><span class="o">::</span><span class="n">OpProtoAndCheckerMaker</span> <span class="p">{</span>
 <span class="k">public</span><span class="o">:</span>
  <span class="n">MulOpMaker</span><span class="p">(</span><span class="n">OpProto</span> <span class="o">*</span><span class="n">proto</span><span class="p">,</span> <span class="n">OpAttrChecker</span> <span class="o">*</span><span class="n">op_checker</span><span class="p">)</span>
      <span class="o">:</span> <span class="n">OpProtoAndCheckerMaker</span><span class="p">(</span><span class="n">proto</span><span class="p">,</span> <span class="n">op_checker</span><span class="p">)</span> <span class="p">{</span>
    <span class="n">AddInput</span><span class="p">(</span><span class="s">&quot;X&quot;</span><span class="p">,</span> <span class="s">&quot;(Tensor), 2D tensor of size (M x K)&quot;</span><span class="p">);</span>
    <span class="n">AddInput</span><span class="p">(</span><span class="s">&quot;Y&quot;</span><span class="p">,</span> <span class="s">&quot;(Tensor), 2D tensor of size (K x N)&quot;</span><span class="p">);</span>
    <span class="n">AddOutput</span><span class="p">(</span><span class="s">&quot;Out&quot;</span><span class="p">,</span> <span class="s">&quot;(Tensor), 2D tensor of size (M x N)&quot;</span><span class="p">);</span>
    <span class="n">AddComment</span><span class="p">(</span><span class="sa">R</span><span class="s">&quot;</span><span class="dl">DOC(</span><span class="s"></span>
<span class="s">Two Element Mul Operator.</span>
<span class="s">The equation is: Out = X * Y</span>
<span class="dl">)DOC</span><span class="s">&quot;</span><span class="p">);</span>
  <span class="p">}</span>
<span class="p">};</span>
</pre></div>
</div>
<p><a class="reference external" href="https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/operators/mul_op.cc#L43"><code class="docutils literal"><span class="pre">MulOpMaker</span></code></a>继承自<code class="docutils literal"><span class="pre">framework::OpProtoAndCheckerMaker</span></code>，构造函数含有2个参数：</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">framework::OpProto</span></code> ： 前者存储Op的输入输出和参数属性，将用于Python API接口的生成。</li>
<li><code class="docutils literal"><span class="pre">framework::OpAttrChecker</span></code> ：后者用于检查参数属性的合法性。</li>
</ul>
<p>构造函数里通过<code class="docutils literal"><span class="pre">AddInput</span></code>添加输入参数，通过<code class="docutils literal"><span class="pre">AddOutput</span></code>添加输出参数，通过<code class="docutils literal"><span class="pre">AddComment</span></code>添加Op的注释。这些函数会将对应内容添加到<code class="docutils literal"><span class="pre">OpProto</span></code>中。</p>
<p>上面的代码在<code class="docutils literal"><span class="pre">MulOp</span></code>中添加两个输入<code class="docutils literal"><span class="pre">X</span></code>和<code class="docutils literal"><span class="pre">Y</span></code>，添加了一个输出<code class="docutils literal"><span class="pre">Out</span></code>，并解释了各自含义，命名请遵守<a class="reference external" href="https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/operators/name_convention.md">命名规范</a>。</p>
<p>再以<a class="reference external" href="https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/operators/scale_op.cc#L37"><code class="docutils literal"><span class="pre">ScaleOp</span></code></a>为例：</p>
<div class="highlight-cpp"><div class="highlight"><pre><span></span><span class="k">template</span> <span class="o">&lt;</span><span class="k">typename</span> <span class="n">AttrType</span><span class="o">&gt;</span>
<span class="k">class</span> <span class="nc">ScaleOpMaker</span> <span class="o">:</span> <span class="k">public</span> <span class="n">framework</span><span class="o">::</span><span class="n">OpProtoAndCheckerMaker</span> <span class="p">{</span>
 <span class="k">public</span><span class="o">:</span>
  <span class="n">ScaleOpMaker</span><span class="p">(</span><span class="n">OpProto</span> <span class="o">*</span><span class="n">proto</span><span class="p">,</span> <span class="n">OpAttrChecker</span> <span class="o">*</span><span class="n">op_checker</span><span class="p">)</span>
      <span class="o">:</span> <span class="n">OpProtoAndCheckerMaker</span><span class="p">(</span><span class="n">proto</span><span class="p">,</span> <span class="n">op_checker</span><span class="p">)</span> <span class="p">{</span>
    <span class="n">AddInput</span><span class="p">(</span><span class="s">&quot;X&quot;</span><span class="p">,</span> <span class="s">&quot;The input tensor of scale operator.&quot;</span><span class="p">).</span><span class="n">NotInGradient</span><span class="p">();</span>
    <span class="n">AddOutput</span><span class="p">(</span><span class="s">&quot;Out&quot;</span><span class="p">,</span> <span class="s">&quot;The output tensor of scale operator.&quot;</span><span class="p">).</span><span class="n">NotInGradient</span><span class="p">();</span>
    <span class="n">AddComment</span><span class="p">(</span><span class="sa">R</span><span class="s">&quot;</span><span class="dl">DOC(</span><span class="s">Scale operator</span>
<span class="s">The equation is: Out = scale*X</span>
<span class="dl">)DOC</span><span class="s">&quot;</span><span class="p">);</span>
    <span class="n">AddAttr</span><span class="o">&lt;</span><span class="n">AttrType</span><span class="o">&gt;</span><span class="p">(</span><span class="s">&quot;scale&quot;</span><span class="p">,</span> <span class="s">&quot;scale of scale operator.&quot;</span><span class="p">).</span><span class="n">SetDefault</span><span class="p">(</span><span class="mf">1.0</span><span class="p">);</span>
  <span class="p">}</span>
<span class="p">};</span>
</pre></div>
</div>
<p>这个例子有两处不同：</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">AddInput(&quot;X&quot;,&quot;...&quot;).NotInGradient()</span></code> : 表示<code class="docutils literal"><span class="pre">X</span></code>这个输入不参与<code class="docutils literal"><span class="pre">ScaleOp</span></code>对应的梯度Op计算之中，如果Op的某个输入不参与反向梯度的计算，请显示地调用<code class="docutils literal"><span class="pre">.NotInGradient()</span></code>进行设置。</li>
<li><code class="docutils literal"><span class="pre">AddAttr&lt;AttrType&gt;(&quot;scale&quot;,</span> <span class="pre">&quot;...&quot;).SetDefault(1.0);</span></code> : 增加<code class="docutils literal"><span class="pre">scale</span></code>系数，作为参数属性，并且设置默认值为1.0。</li>
</ul>
</div>
<div class="section" id="operator">
<span id="id2"></span><h3>定义Operator类<a class="headerlink" href="#operator" title="永久链接至标题">¶</a></h3>
<p>下面的点实现了MulOp的定义：</p>
<div class="highlight-cpp"><div class="highlight"><pre><span></span><span class="k">class</span> <span class="nc">MulOp</span> <span class="o">:</span> <span class="k">public</span> <span class="n">framework</span><span class="o">::</span><span class="n">OperatorWithKernel</span> <span class="p">{</span>
 <span class="k">public</span><span class="o">:</span>
  <span class="k">using</span> <span class="n">framework</span><span class="o">::</span><span class="n">OperatorWithKernel</span><span class="o">::</span><span class="n">OperatorWithKernel</span><span class="p">;</span>

 <span class="k">protected</span><span class="o">:</span>
  <span class="kt">void</span> <span class="n">InferShape</span><span class="p">(</span><span class="k">const</span> <span class="n">framework</span><span class="o">::</span><span class="n">InferShapeContext</span> <span class="o">&amp;</span><span class="n">ctx</span><span class="p">)</span> <span class="k">const</span> <span class="k">override</span> <span class="p">{</span>
    <span class="k">auto</span> <span class="n">dim0</span> <span class="o">=</span> <span class="n">ctx</span><span class="p">.</span><span class="n">Input</span><span class="o">&lt;</span><span class="n">Tensor</span><span class="o">&gt;</span><span class="p">(</span><span class="s">&quot;X&quot;</span><span class="p">)</span><span class="o">-&gt;</span><span class="n">dims</span><span class="p">();</span>
    <span class="k">auto</span> <span class="n">dim1</span> <span class="o">=</span> <span class="n">ctx</span><span class="p">.</span><span class="n">Input</span><span class="o">&lt;</span><span class="n">Tensor</span><span class="o">&gt;</span><span class="p">(</span><span class="s">&quot;Y&quot;</span><span class="p">)</span><span class="o">-&gt;</span><span class="n">dims</span><span class="p">();</span>
    <span class="n">PADDLE_ENFORCE_EQ</span><span class="p">(</span><span class="n">dim0</span><span class="p">.</span><span class="n">size</span><span class="p">(),</span> <span class="mi">2</span><span class="p">,</span>
                      <span class="s">&quot;input X(%s) should be a tensor with 2 dims, a matrix&quot;</span><span class="p">,</span>
                      <span class="n">ctx</span><span class="p">.</span><span class="n">op_</span><span class="p">.</span><span class="n">Input</span><span class="p">(</span><span class="s">&quot;X&quot;</span><span class="p">));</span>
    <span class="n">PADDLE_ENFORCE_EQ</span><span class="p">(</span><span class="n">dim1</span><span class="p">.</span><span class="n">size</span><span class="p">(),</span> <span class="mi">2</span><span class="p">,</span>
                      <span class="s">&quot;input Y(%s) should be a tensor with 2 dims, a matrix&quot;</span><span class="p">,</span>
                      <span class="n">ctx</span><span class="p">.</span><span class="n">op_</span><span class="p">.</span><span class="n">Input</span><span class="p">(</span><span class="s">&quot;Y&quot;</span><span class="p">));</span>
    <span class="n">PADDLE_ENFORCE_EQ</span><span class="p">(</span>
        <span class="n">dim0</span><span class="p">[</span><span class="mi">1</span><span class="p">],</span> <span class="n">dim1</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span>
        <span class="s">&quot;First matrix&#39;s width must be equal with second matrix&#39;s height.&quot;</span><span class="p">);</span>
    <span class="n">ctx</span><span class="p">.</span><span class="n">Output</span><span class="o">&lt;</span><span class="n">Tensor</span><span class="o">&gt;</span><span class="p">(</span><span class="s">&quot;Out&quot;</span><span class="p">)</span><span class="o">-&gt;</span><span class="n">Resize</span><span class="p">({</span><span class="n">dim0</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="n">dim1</span><span class="p">[</span><span class="mi">1</span><span class="p">]});</span>
  <span class="p">}</span>
<span class="p">};</span>
</pre></div>
</div>
<p><a class="reference external" href="https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/operators/mul_op.cc#L22"><code class="docutils literal"><span class="pre">MulOp</span></code></a>继承自<code class="docutils literal"><span class="pre">OperatorWithKernel</span></code>。<code class="docutils literal"><span class="pre">public</span></code>成员：</p>
<div class="highlight-cpp"><div class="highlight"><pre><span></span><span class="k">using</span> <span class="n">framework</span><span class="o">::</span><span class="n">OperatorWithKernel</span><span class="o">::</span><span class="n">OperatorWithKernel</span><span class="p">;</span>
</pre></div>
</div>
<p>这句表示使用基类<code class="docutils literal"><span class="pre">OperatorWithKernel</span></code>的构造函数，也可写成：</p>
<div class="highlight-cpp"><div class="highlight"><pre><span></span><span class="n">MulOp</span><span class="p">(</span><span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="o">&amp;</span><span class="n">type</span><span class="p">,</span> <span class="k">const</span> <span class="n">framework</span><span class="o">::</span><span class="n">VariableNameMap</span> <span class="o">&amp;</span><span class="n">inputs</span><span class="p">,</span>
      <span class="k">const</span> <span class="n">framework</span><span class="o">::</span><span class="n">VariableNameMap</span> <span class="o">&amp;</span><span class="n">outputs</span><span class="p">,</span>
      <span class="k">const</span> <span class="n">framework</span><span class="o">::</span><span class="n">AttributeMap</span> <span class="o">&amp;</span><span class="n">attrs</span><span class="p">)</span>
  <span class="o">:</span> <span class="n">OperatorWithKernel</span><span class="p">(</span><span class="n">type</span><span class="p">,</span> <span class="n">inputs</span><span class="p">,</span> <span class="n">outputs</span><span class="p">,</span> <span class="n">attrs</span><span class="p">)</span> <span class="p">{}</span>
</pre></div>
</div>
<p>还需要重写<code class="docutils literal"><span class="pre">InferShape</span></code>接口。<code class="docutils literal"><span class="pre">InferShape</span></code>为const函数，不能修改Op的成员变量，参数为<code class="docutils literal"><span class="pre">const</span> <span class="pre">framework::InferShapeContext</span> <span class="pre">&amp;ctx</span></code>，通过该参数可获取到输入输出以及属性。它的功能是：</p>
<ul class="simple">
<li>1). 做检查， 尽早报错：检查输入数据维度、类型等是否合法。</li>
<li>2). 设置输出Tensor的形状。</li>
</ul>
<p>通常<code class="docutils literal"><span class="pre">OpProtoMaker</span></code>和<code class="docutils literal"><span class="pre">Op</span></code>类的定义写在<code class="docutils literal"><span class="pre">.cc</span></code>文件中，和下面将要介绍的注册函数一起放在<code class="docutils literal"><span class="pre">.cc</span></code>中</p>
</div>
<div class="section" id="opkernel">
<span id="opkernel"></span><h3>定义OpKernel类<a class="headerlink" href="#opkernel" title="永久链接至标题">¶</a></h3>
<p><code class="docutils literal"><span class="pre">MulKernel</span></code>继承自<code class="docutils literal"><span class="pre">framework::OpKernel</span></code>，带有下面两个模板参数:</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">typename</span> <span class="pre">DeviceContext</span></code>: 表示设备类型，不同设备(CPU、CUDA)共享同一个Kernel时，需加该模板参数，不共享则不加，一个不共享的例子是<a class="reference external" href="https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/operators/cross_entropy_op.h#L43"><code class="docutils literal"><span class="pre">OnehotCrossEntropyOpKernel</span></code></a>。</li>
<li><code class="docutils literal"><span class="pre">typename</span> <span class="pre">T</span></code> : 表示数据类型，如<code class="docutils literal"><span class="pre">float</span></code>, <code class="docutils literal"><span class="pre">double</span></code>等。</li>
</ul>
<p>需要为<code class="docutils literal"><span class="pre">MulKernel</span></code>类重写<code class="docutils literal"><span class="pre">Compute</span></code>接口。</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">Compute</span></code>接受一个输入参数：<code class="docutils literal"><span class="pre">const</span> <span class="pre">framework::ExecutionContext&amp;</span> <span class="pre">context</span></code>。</li>
<li>与<code class="docutils literal"><span class="pre">InferShapeContext</span></code>相比，<code class="docutils literal"><span class="pre">ExecutionContext</span></code>增加了设备类型，同样可获取到输入输出和属性参数。</li>
<li><code class="docutils literal"><span class="pre">Compute</span></code>函数里实现<code class="docutils literal"><span class="pre">OpKernel</span></code>的具体计算逻辑。</li>
</ul>
<p>下面是 <code class="docutils literal"><span class="pre">MulKernel</span></code> <code class="docutils literal"><span class="pre">Compute</span></code>的实现：</p>
<div class="highlight-cpp"><div class="highlight"><pre><span></span><span class="k">template</span> <span class="o">&lt;</span><span class="k">typename</span> <span class="n">DeviceContext</span><span class="p">,</span> <span class="k">typename</span> <span class="n">T</span><span class="o">&gt;</span>
<span class="k">class</span> <span class="nc">MulKernel</span> <span class="o">:</span> <span class="k">public</span> <span class="n">framework</span><span class="o">::</span><span class="n">OpKernel</span> <span class="p">{</span>
<span class="k">public</span><span class="o">:</span>
<span class="kt">void</span> <span class="n">Compute</span><span class="p">(</span><span class="k">const</span> <span class="n">framework</span><span class="o">::</span><span class="n">ExecutionContext</span><span class="o">&amp;</span> <span class="n">context</span><span class="p">)</span> <span class="k">const</span> <span class="k">override</span> <span class="p">{</span>
  <span class="k">auto</span><span class="o">*</span> <span class="n">X</span> <span class="o">=</span> <span class="n">context</span><span class="p">.</span><span class="n">Input</span><span class="o">&lt;</span><span class="n">Tensor</span><span class="o">&gt;</span><span class="p">(</span><span class="s">&quot;X&quot;</span><span class="p">);</span>
  <span class="k">auto</span><span class="o">*</span> <span class="n">Y</span> <span class="o">=</span> <span class="n">context</span><span class="p">.</span><span class="n">Input</span><span class="o">&lt;</span><span class="n">Tensor</span><span class="o">&gt;</span><span class="p">(</span><span class="s">&quot;Y&quot;</span><span class="p">);</span>
  <span class="k">auto</span><span class="o">*</span> <span class="n">Z</span> <span class="o">=</span> <span class="n">context</span><span class="p">.</span><span class="n">Output</span><span class="o">&lt;</span><span class="n">Tensor</span><span class="o">&gt;</span><span class="p">(</span><span class="s">&quot;Out&quot;</span><span class="p">);</span>
  <span class="n">Z</span><span class="o">-&gt;</span><span class="n">mutable_data</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="p">(</span><span class="n">context</span><span class="p">.</span><span class="n">GetPlace</span><span class="p">());</span>
  <span class="k">auto</span><span class="o">&amp;</span> <span class="n">device_context</span> <span class="o">=</span> <span class="n">context</span><span class="p">.</span><span class="k">template</span> <span class="n">device_context</span><span class="o">&lt;</span><span class="n">DeviceContext</span><span class="o">&gt;</span><span class="p">();</span>
  <span class="n">math</span><span class="o">::</span><span class="n">matmul</span><span class="o">&lt;</span><span class="n">DeviceContext</span><span class="p">,</span> <span class="n">T</span><span class="o">&gt;</span><span class="p">(</span><span class="o">*</span><span class="n">X</span><span class="p">,</span> <span class="nb">false</span><span class="p">,</span> <span class="o">*</span><span class="n">Y</span><span class="p">,</span> <span class="nb">false</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">Z</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">device_context</span><span class="p">);</span>
<span class="p">}</span>
<span class="p">};</span>
</pre></div>
</div>
<p>需要注意：<strong>不同设备(CPU、CUDA)共享一个Op定义，是否则共享同一个<code class="docutils literal"><span class="pre">OpKernel</span></code>，取决于<code class="docutils literal"><span class="pre">Compute</span></code>调用的函数是否支持不同设备。</strong></p>
<p><code class="docutils literal"><span class="pre">MulOp</span></code>的CPU、CUDA实现共享同一个<code class="docutils literal"><span class="pre">Kernel</span></code>。<code class="docutils literal"><span class="pre">OpKernel</span></code>不共享的例子可以参考：<a class="reference external" href="https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/operators/cross_entropy_op.h#L43"><code class="docutils literal"><span class="pre">OnehotCrossEntropyOpKernel</span></code></a>。</p>
<p>为了使<code class="docutils literal"><span class="pre">OpKernel</span></code>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<code class="docutils literal"><span class="pre">Compute</span></code>接口。关于在PaddlePaddle中如何使用Eigen库，请参考<a class="reference external" href="https://github.com/PaddlePaddle/Paddle/blob/develop/doc/howto/dev/use_eigen_cn.md">使用文档</a>。</p>
<p>到此，前向Op实现完成。接下来，需要在<code class="docutils literal"><span class="pre">.cc</span></code>文件中注册该op和kernel。
反向Op类的定义，反向OpKernel的定义与前向Op类似，这里不再赘述。<strong>但需注意反向Op没有<code class="docutils literal"><span class="pre">ProtoMaker</span></code></strong>。</p>
</div>
<div class="section" id="operator">
<span id="id3"></span><h3>注册Operator<a class="headerlink" href="#operator" title="永久链接至标题">¶</a></h3>
<ul>
<li><p class="first">在<code class="docutils literal"><span class="pre">.cc</span></code>文件中注册前向、反向Op类，注册CPU Kernel。</p>
<div class="highlight-cpp"><div class="highlight"><pre><span></span><span class="k">namespace</span> <span class="n">ops</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">::</span><span class="n">operators</span><span class="p">;</span>
<span class="n">REGISTER_OP</span><span class="p">(</span><span class="n">mul</span><span class="p">,</span> <span class="n">ops</span><span class="o">::</span><span class="n">MulOp</span><span class="p">,</span> <span class="n">ops</span><span class="o">::</span><span class="n">MulOpMaker</span><span class="p">,</span> <span class="n">mul_grad</span><span class="p">,</span> <span class="n">ops</span><span class="o">::</span><span class="n">MulOpGrad</span><span class="p">);</span>
<span class="n">REGISTER_OP_CPU_KERNEL</span><span class="p">(</span><span class="n">mul</span><span class="p">,</span> <span class="n">ops</span><span class="o">::</span><span class="n">MulKernel</span><span class="o">&lt;</span><span class="n">paddle</span><span class="o">::</span><span class="n">platform</span><span class="o">::</span><span class="n">CPUDeviceContext</span><span class="p">,</span> <span class="kt">float</span><span class="o">&gt;</span><span class="p">);</span>
<span class="n">REGISTER_OP_CPU_KERNEL</span><span class="p">(</span><span class="n">mul_grad</span><span class="p">,</span>
              <span class="n">ops</span><span class="o">::</span><span class="n">MulGradKernel</span><span class="o">&lt;</span><span class="n">paddle</span><span class="o">::</span><span class="n">platform</span><span class="o">::</span><span class="n">CPUDeviceContext</span><span class="p">,</span> <span class="kt">float</span><span class="o">&gt;</span><span class="p">);</span>
</pre></div>
</div>
<p>在上面的代码中：</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">REGISTER_OP</span></code> ： 注册<code class="docutils literal"><span class="pre">ops::MulOp</span></code>类，类型名为<code class="docutils literal"><span class="pre">mul</span></code>，该类的<code class="docutils literal"><span class="pre">ProtoMaker</span></code>为<code class="docutils literal"><span class="pre">ops::MulOpMaker</span></code>，注册<code class="docutils literal"><span class="pre">ops::MulOpGrad</span></code>，类型名为<code class="docutils literal"><span class="pre">mul_grad</span></code>。</li>
<li><code class="docutils literal"><span class="pre">REGISTER_OP_WITHOUT_GRADIENT</span></code> ： 用于注册没有反向的Op。</li>
<li><code class="docutils literal"><span class="pre">REGISTER_OP_CPU_KERNEL</span></code> ：注册<code class="docutils literal"><span class="pre">ops::MulKernel</span></code>类，并特化模板参数为<code class="docutils literal"><span class="pre">paddle::platform::CPUPlace</span></code>和<code class="docutils literal"><span class="pre">float</span></code>类型，同理，注册<code class="docutils literal"><span class="pre">ops::MulGradKernel</span></code>类。</li>
</ul>
</li>
</ul>
<ul>
<li><p class="first">在 <code class="docutils literal"><span class="pre">.cu</span></code>文件中注册CUDA Kernel。</p>
<ul class="simple">
<li>请注意，如果CUDA Kernel的实现基于Eigen unsupported模块，那么在 <code class="docutils literal"><span class="pre">.cu</span></code>的开始请加上宏定义 <code class="docutils literal"><span class="pre">#define</span> <span class="pre">EIGEN_USE_GPU</span></code>，代码示例如下：</li>
</ul>
<div class="highlight-cpp"><div class="highlight"><pre><span></span><span class="c1">// if use Eigen unsupported module before include head files</span>
<span class="cp">#define EIGEN_USE_GPU</span>

<span class="k">namespace</span> <span class="n">ops</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">::</span><span class="n">operators</span><span class="p">;</span>
<span class="n">REGISTER_OP_CUDA_KERNEL</span><span class="p">(</span><span class="n">mul</span><span class="p">,</span> <span class="n">ops</span><span class="o">::</span><span class="n">MulKernel</span><span class="o">&lt;</span><span class="n">paddle</span><span class="o">::</span><span class="n">platform</span><span class="o">::</span><span class="n">CUDADeviceContext</span><span class="p">,</span> <span class="kt">float</span><span class="o">&gt;</span><span class="p">);</span>
<span class="n">REGISTER_OP_CUDA_KERNEL</span><span class="p">(</span><span class="n">mul_grad</span><span class="p">,</span>
                       <span class="n">ops</span><span class="o">::</span><span class="n">MulGradKernel</span><span class="o">&lt;</span><span class="n">paddle</span><span class="o">::</span><span class="n">platform</span><span class="o">::</span><span class="n">CUDADeviceContext</span><span class="p">,</span> <span class="kt">float</span><span class="o">&gt;</span><span class="p">);</span>
</pre></div>
</div>
</li>
</ul>
</div>
<div class="section" id="">
<span id="id4"></span><h3>编译<a class="headerlink" href="#" title="永久链接至标题">¶</a></h3>
<p>运行下面命令可以进行编译：</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">make</span> <span class="n">mul_op</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="python">
<span id="python"></span><h2>绑定Python<a class="headerlink" href="#python" title="永久链接至标题">¶</a></h2>
<p>系统会对新增的op自动绑定Python，并链接到生成的lib库中。</p>
</div>
<div class="section" id="">
<span id="id5"></span><h2>实现单元测试<a class="headerlink" href="#" title="永久链接至标题">¶</a></h2>
<p>单测包括对比前向Op不同设备(CPU、CUDA)的实现、对比反向OP不同设备(CPU、CUDA)的实现、反向Op的梯度测试。下面介绍介绍<a class="reference external" href="https://github.com/PaddlePaddle/Paddle/blob/develop/python/paddle/v2/framework/tests/test_mul_op.py"><code class="docutils literal"><span class="pre">MulOp</span></code>的单元测试</a>。</p>
<div class="section" id="operator">
<span id="id6"></span><h3>前向Operator单测<a class="headerlink" href="#operator" title="永久链接至标题">¶</a></h3>
<p>Op单元测试继承自<code class="docutils literal"><span class="pre">OpTest</span></code>。各项更加具体的单元测试在<code class="docutils literal"><span class="pre">TestMulOp</span></code>里完成。测试Operator，需要：</p>
<ol class="simple">
<li>在<code class="docutils literal"><span class="pre">setUp</span></code>函数定义输入、输出，以及相关的属性参数。</li>
<li>生成随机的输入数据。</li>
<li>在Python脚本中实现与前向operator相同的计算逻辑，得到输出值，与operator前向计算的输出进行对比。</li>
<li>反向计算已经自动集成进测试框架，直接调用相应接口即可。</li>
</ol>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">unittest</span>
<span class="kn">import</span> <span class="nn">numpy</span> <span class="kn">as</span> <span class="nn">np</span>
<span class="kn">from</span> <span class="nn">op_test</span> <span class="kn">import</span> <span class="n">OpTest</span>


<span class="k">class</span> <span class="nc">TestMulOp</span><span class="p">(</span><span class="n">OpTest</span><span class="p">):</span>
    <span class="k">def</span> <span class="nf">setUp</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">op_type</span> <span class="o">=</span> <span class="s2">&quot;mul&quot;</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">inputs</span> <span class="o">=</span> <span class="p">{</span>
            <span class="s1">&#39;X&#39;</span><span class="p">:</span> <span class="n">np</span><span class="o">.</span><span class="n">random</span><span class="o">.</span><span class="n">random</span><span class="p">((</span><span class="mi">32</span><span class="p">,</span> <span class="mi">84</span><span class="p">))</span><span class="o">.</span><span class="n">astype</span><span class="p">(</span><span class="s2">&quot;float32&quot;</span><span class="p">),</span>
            <span class="s1">&#39;Y&#39;</span><span class="p">:</span> <span class="n">np</span><span class="o">.</span><span class="n">random</span><span class="o">.</span><span class="n">random</span><span class="p">((</span><span class="mi">84</span><span class="p">,</span> <span class="mi">100</span><span class="p">))</span><span class="o">.</span><span class="n">astype</span><span class="p">(</span><span class="s2">&quot;float32&quot;</span><span class="p">)</span>
        <span class="p">}</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">outputs</span> <span class="o">=</span> <span class="p">{</span><span class="s1">&#39;Out&#39;</span><span class="p">:</span> <span class="n">np</span><span class="o">.</span><span class="n">dot</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">inputs</span><span class="p">[</span><span class="s1">&#39;X&#39;</span><span class="p">],</span> <span class="bp">self</span><span class="o">.</span><span class="n">inputs</span><span class="p">[</span><span class="s1">&#39;Y&#39;</span><span class="p">])}</span>

    <span class="k">def</span> <span class="nf">test_check_output</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">check_output</span><span class="p">()</span>

    <span class="k">def</span> <span class="nf">test_check_grad_normal</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">check_grad</span><span class="p">([</span><span class="s1">&#39;X&#39;</span><span class="p">,</span> <span class="s1">&#39;Y&#39;</span><span class="p">],</span> <span class="s1">&#39;Out&#39;</span><span class="p">,</span> <span class="n">max_relative_error</span><span class="o">=</span><span class="mf">0.5</span><span class="p">)</span>

    <span class="k">def</span> <span class="nf">test_check_grad_ingore_x</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">check_grad</span><span class="p">(</span>
            <span class="p">[</span><span class="s1">&#39;Y&#39;</span><span class="p">],</span> <span class="s1">&#39;Out&#39;</span><span class="p">,</span> <span class="n">max_relative_error</span><span class="o">=</span><span class="mf">0.5</span><span class="p">,</span> <span class="n">no_grad_set</span><span class="o">=</span><span class="nb">set</span><span class="p">(</span><span class="s2">&quot;X&quot;</span><span class="p">))</span>

    <span class="k">def</span> <span class="nf">test_check_grad_ingore_y</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">check_grad</span><span class="p">(</span>
            <span class="p">[</span><span class="s1">&#39;X&#39;</span><span class="p">],</span> <span class="s1">&#39;Out&#39;</span><span class="p">,</span> <span class="n">max_relative_error</span><span class="o">=</span><span class="mf">0.5</span><span class="p">,</span> <span class="n">no_grad_set</span><span class="o">=</span><span class="nb">set</span><span class="p">(</span><span class="s1">&#39;Y&#39;</span><span class="p">))</span>
</pre></div>
</div>
<p>上面的代码首先导入依赖的包，下面是对<code class="docutils literal"><span class="pre">setUp</span></code>函数中操作的重要变量的详细解释：</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">self.op_type</span> <span class="pre">=</span> <span class="pre">&quot;mul&quot;</span></code> : 定义类型，与operator注册时注册的类型一致。</li>
<li><code class="docutils literal"><span class="pre">self.inputs</span></code> : 定义输入，类型为<code class="docutils literal"><span class="pre">numpy.array</span></code>，并初始化。</li>
<li><code class="docutils literal"><span class="pre">self.outputs</span></code> : 定义输出，并在Python脚本中完成与operator同样的计算逻辑，返回Python端的计算结果。</li>
</ul>
</div>
<div class="section" id="operator">
<span id="id7"></span><h3>反向operator单测<a class="headerlink" href="#operator" title="永久链接至标题">¶</a></h3>
<p>而反向测试中：</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">test_check_grad_normal</span></code>中调用<code class="docutils literal"><span class="pre">check_grad</span></code>使用数值法检测梯度正确性和稳定性。<ul>
<li>第一个参数<code class="docutils literal"><span class="pre">[&quot;X&quot;,</span> <span class="pre">&quot;Y&quot;]</span></code> : 指定对输入变量<code class="docutils literal"><span class="pre">X</span></code>、<code class="docutils literal"><span class="pre">Y</span></code>做梯度检测。</li>
<li>第二个参数<code class="docutils literal"><span class="pre">&quot;Out&quot;</span></code> : 指定前向网络最终的输出目标变量<code class="docutils literal"><span class="pre">Out</span></code>。</li>
<li>第三个参数<code class="docutils literal"><span class="pre">max_relative_error</span></code>：指定检测梯度时能容忍的最大错误值。</li>
</ul>
</li>
<li><code class="docutils literal"><span class="pre">test_check_grad_ingore_x</span></code>和<code class="docutils literal"><span class="pre">test_check_grad_ingore_y</span></code>分支用来测试只需要计算一个输入梯度的情况。</li>
</ul>
</div>
<div class="section" id="">
<span id="id8"></span><h3>编译和执行<a class="headerlink" href="#" title="永久链接至标题">¶</a></h3>
<p><code class="docutils literal"><span class="pre">python/paddle/v2/framework/tests</span></code> 目录下新增的 <code class="docutils literal"><span class="pre">test_*.py</span></code> 单元测试会被自动加入工程进行编译。</p>
<p>请注意，<strong>不同于Op的编译测试，运行单元测试测时需要编译整个工程</strong>，并且编译时需要打开<code class="docutils literal"><span class="pre">WITH_TESTING</span></code>, 即<code class="docutils literal"><span class="pre">cmake</span> <span class="pre">paddle_dir</span> <span class="pre">-DWITH_TESTING=ON</span></code>。编译成功后，执行下面的命令来运行单元测试：</p>
<div class="highlight-bash"><div class="highlight"><pre><span></span>make <span class="nb">test</span> <span class="nv">ARGS</span><span class="o">=</span><span class="s2">&quot;-R test_mul_op -V&quot;</span>
</pre></div>
</div>
<p>或者:</p>
<div class="highlight-bash"><div class="highlight"><pre><span></span>ctest -R test_mul_op
</pre></div>
</div>
</div>
</div>
<div class="section" id="">
<span id="id9"></span><h2>注意事项<a class="headerlink" href="#" title="永久链接至标题">¶</a></h2>
<ul class="simple">
<li>为每个Op创建单独的<code class="docutils literal"><span class="pre">*_op.h</span></code>（如有）、<code class="docutils literal"><span class="pre">*_op.cc</span></code>和<code class="docutils literal"><span class="pre">*_op.cu</span></code>（如有）。不允许一个文件中包含多个Op，这将会导致编译出错。</li>
<li>注册Op时的类型名，需要和该Op的名字一样。即不允许在<code class="docutils literal"><span class="pre">A_op.cc</span></code>里面，注册<code class="docutils literal"><span class="pre">REGISTER_OP(B,</span> <span class="pre">...)</span></code>等，这将会导致单元测试出错。</li>
<li>如果Op没有实现CUDA Kernel，请不要创建空的<code class="docutils literal"><span class="pre">*_op.cu</span></code>，这将会导致单元测试出错。</li>
<li>如果多个Op依赖一些共用的函数，可以创建非<code class="docutils literal"><span class="pre">*_op.*</span></code>格式的文件来存放，如<code class="docutils literal"><span class="pre">gather.h</span></code>文件。</li>
</ul>
</div>
</div>


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