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| <div class="section" id="customized-loss-function"> |
| <span id="customized-loss-function"></span><h1>Customized loss function<a class="headerlink" href="#customized-loss-function" title="Permalink to this headline">¶</a></h1> |
| <p>This tutorial provides guidelines for using customized loss function in network construction.</p> |
| <div class="section" id="model-training-example"> |
| <span id="model-training-example"></span><h2>Model Training Example<a class="headerlink" href="#model-training-example" title="Permalink to this headline">¶</a></h2> |
| <p>Let’s begin with a small regression example. We can build and train a regression model with the following code:</p> |
| <div class="highlight-r"><div class="highlight"><pre><span></span> <span class="kn">library</span><span class="p">(</span>mxnet<span class="p">)</span> |
| data<span class="p">(</span>BostonHousing<span class="p">,</span> package<span class="o">=</span><span class="s">"mlbench"</span><span class="p">)</span> |
| train.ind <span class="o">=</span> <span class="kp">seq</span><span class="p">(</span><span class="m">1</span><span class="p">,</span> <span class="m">506</span><span class="p">,</span> <span class="m">3</span><span class="p">)</span> |
| train.x <span class="o">=</span> <span class="kp">data.matrix</span><span class="p">(</span>BostonHousing<span class="p">[</span>train.ind<span class="p">,</span> <span class="m">-14</span><span class="p">])</span> |
| train.y <span class="o">=</span> BostonHousing<span class="p">[</span>train.ind<span class="p">,</span> <span class="m">14</span><span class="p">]</span> |
| test.x <span class="o">=</span> <span class="kp">data.matrix</span><span class="p">(</span>BostonHousing<span class="p">[</span><span class="o">-</span>train.ind<span class="p">,</span> <span class="m">-14</span><span class="p">])</span> |
| test.y <span class="o">=</span> BostonHousing<span class="p">[</span><span class="o">-</span>train.ind<span class="p">,</span> <span class="m">14</span><span class="p">]</span> |
| data <span class="o"><-</span> mx.symbol.Variable<span class="p">(</span><span class="s">"data"</span><span class="p">)</span> |
| fc1 <span class="o"><-</span> mx.symbol.FullyConnected<span class="p">(</span>data<span class="p">,</span> num_hidden<span class="o">=</span><span class="m">1</span><span class="p">)</span> |
| lro <span class="o"><-</span> mx.symbol.LinearRegressionOutput<span class="p">(</span>fc1<span class="p">)</span> |
| mx.set.seed<span class="p">(</span><span class="m">0</span><span class="p">)</span> |
| model <span class="o"><-</span> mx.model.FeedForward.create<span class="p">(</span> |
| lro<span class="p">,</span> X<span class="o">=</span>train.x<span class="p">,</span> y<span class="o">=</span>train.y<span class="p">,</span> |
| eval.data<span class="o">=</span><span class="kt">list</span><span class="p">(</span>data<span class="o">=</span>test.x<span class="p">,</span> label<span class="o">=</span>test.y<span class="p">),</span> |
| ctx<span class="o">=</span>mx.cpu<span class="p">(),</span> num.round<span class="o">=</span><span class="m">10</span><span class="p">,</span> array.batch.size<span class="o">=</span><span class="m">20</span><span class="p">,</span> |
| learning.rate<span class="o">=</span><span class="m">2e-6</span><span class="p">,</span> momentum<span class="o">=</span><span class="m">0.9</span><span class="p">,</span> eval.metric<span class="o">=</span>mx.metric.rmse<span class="p">)</span> |
| </pre></div> |
| </div> |
| <p>Besides the <code class="docutils literal"><span class="pre">LinearRegressionOutput</span></code>, we also provide <code class="docutils literal"><span class="pre">LogisticRegressionOutput</span></code> and <code class="docutils literal"><span class="pre">MAERegressionOutput</span></code>. |
| However, this might not be enough for real-world models. You can provide your own loss function |
| by using <code class="docutils literal"><span class="pre">mx.symbol.MakeLoss</span></code> when constructing the network.</p> |
| </div> |
| <div class="section" id="how-to-use-your-own-loss-function"> |
| <span id="how-to-use-your-own-loss-function"></span><h2>How to Use Your Own Loss Function<a class="headerlink" href="#how-to-use-your-own-loss-function" title="Permalink to this headline">¶</a></h2> |
| <p>We still use our previous example.</p> |
| <div class="highlight-r"><div class="highlight"><pre><span></span> <span class="kn">library</span><span class="p">(</span>mxnet<span class="p">)</span> |
| data <span class="o"><-</span> mx.symbol.Variable<span class="p">(</span><span class="s">"data"</span><span class="p">)</span> |
| fc1 <span class="o"><-</span> mx.symbol.FullyConnected<span class="p">(</span>data<span class="p">,</span> num_hidden<span class="o">=</span><span class="m">1</span><span class="p">)</span> |
| lro <span class="o"><-</span> mx.symbol.MakeLoss<span class="p">(</span>mx.symbol.square<span class="p">(</span>mx.symbol.Reshape<span class="p">(</span>fc1<span class="p">,</span> shape <span class="o">=</span> <span class="m">0</span><span class="p">)</span> <span class="o">-</span> label<span class="p">))</span> |
| </pre></div> |
| </div> |
| <p>In the last line of network definition, we do not use the predefined loss function. We define the loss |
| by ourselves, which is <code class="docutils literal"><span class="pre">(pred-label)^2</span></code>.</p> |
| <p>We have provided many operations on the symbols, so you can also define <code class="docutils literal"><span class="pre">|pred-label|</span></code> using the line below.</p> |
| <div class="highlight-r"><div class="highlight"><pre><span></span> lro <span class="o"><-</span> mx.symbol.MakeLoss<span class="p">(</span>mx.symbol.abs<span class="p">(</span>mx.symbol.Reshape<span class="p">(</span>fc1<span class="p">,</span> shape <span class="o">=</span> <span class="m">0</span><span class="p">)</span> <span class="o">-</span> label<span class="p">))</span> |
| </pre></div> |
| </div> |
| </div> |
| <div class="section" id="next-steps"> |
| <span id="next-steps"></span><h2>Next Steps<a class="headerlink" href="#next-steps" title="Permalink to this headline">¶</a></h2> |
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| <li class="toctree-l1"><a class="reference external" href="http://mxnet.io/tutorials/r/fiveMinutesNeuralNetwork.html">Neural Networks with MXNet in Five Minutes</a></li> |
| <li class="toctree-l1"><a class="reference external" href="http://mxnet.io/tutorials/r/classifyRealImageWithPretrainedModel.html">Classify Real-World Images with a PreTrained Model</a></li> |
| <li class="toctree-l1"><a class="reference external" href="http://mxnet.io/tutorials/r/mnistCompetition.html">Handwritten Digits Classification Competition</a></li> |
| <li class="toctree-l1"><a class="reference external" href="http://mxnet.io/tutorials/r/charRnnModel.html">Character Language Model Using RNN</a></li> |
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| <h3><a href="../../index.html">Table Of Contents</a></h3> |
| <ul> |
| <li><a class="reference internal" href="#">Customized loss function</a><ul> |
| <li><a class="reference internal" href="#model-training-example">Model Training Example</a></li> |
| <li><a class="reference internal" href="#how-to-use-your-own-loss-function">How to Use Your Own Loss Function</a></li> |
| <li><a class="reference internal" href="#next-steps">Next Steps</a></li> |
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