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<div class="section" id="module-neural-network-training-and-inference">
<span id="module-neural-network-training-and-inference"></span><h1>Module - Neural network training and inference<a class="headerlink" href="#module-neural-network-training-and-inference" title="Permalink to this headline"></a></h1>
<p>Training a neural network involves quite a few steps. One need to specify how
to feed input training data, initialize model parameters, perform forward and
backward passes through the network, update weights based on computed gradients, do
model checkpoints, etc. During prediction, one ends up repeating most of these
steps. All this can be quite daunting to both newcomers as well as experienced
developers.</p>
<p>Luckily, MXNet modularizes commonly used code for training and inference in
the <code class="docutils literal"><span class="pre">module</span></code> (<code class="docutils literal"><span class="pre">mod</span></code> for short) package. <code class="docutils literal"><span class="pre">Module</span></code> provides both high-level and
intermediate-level interfaces for executing predefined networks. One can use
both interfaces interchangeably. We will show the usage of both interfaces in
this tutorial.</p>
<div class="section" id="prerequisites">
<span id="prerequisites"></span><h2>Prerequisites<a class="headerlink" href="#prerequisites" title="Permalink to this headline"></a></h2>
<p>To complete this tutorial, we need:</p>
<ul class="simple">
<li>MXNet. See the instructions for your operating system in <a class="reference external" href="/versions/1.1.0/install/index.html">Setup and Installation</a>.</li>
<li><a class="reference external" href="http://jupyter.org/index.html">Jupyter Notebook</a> and <a class="reference external" href="http://docs.python-requests.org/en/master/">Python Requests</a> packages.</li>
</ul>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">pip</span> <span class="n">install</span> <span class="n">jupyter</span> <span class="n">requests</span>
</pre></div>
</div>
</div>
<div class="section" id="preliminary">
<span id="preliminary"></span><h2>Preliminary<a class="headerlink" href="#preliminary" title="Permalink to this headline"></a></h2>
<p>In this tutorial we will demonstrate <code class="docutils literal"><span class="pre">module</span></code> usage by training a
<a class="reference external" href="https://en.wikipedia.org/wiki/Multilayer_perceptron">Multilayer Perceptron</a> (MLP)
on the <a class="reference external" href="https://archive.ics.uci.edu/ml/datasets/letter+recognition">UCI letter recognition</a>
dataset.</p>
<p>The following code downloads the dataset and creates an 80:20 train:test
split. It also initializes a training data iterator to return a batch of 32
training examples each time. A separate iterator is also created for test data.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">logging</span>
<span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">()</span><span class="o">.</span><span class="n">setLevel</span><span class="p">(</span><span class="n">logging</span><span class="o">.</span><span class="n">INFO</span><span class="p">)</span>
<span class="kn">import</span> <span class="nn">mxnet</span> <span class="kn">as</span> <span class="nn">mx</span>
<span class="kn">import</span> <span class="nn">numpy</span> <span class="kn">as</span> <span class="nn">np</span>
<span class="n">fname</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">test_utils</span><span class="o">.</span><span class="n">download</span><span class="p">(</span><span class="s1">'http://archive.ics.uci.edu/ml/machine-learning-databases/letter-recognition/letter-recognition.data'</span><span class="p">)</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">genfromtxt</span><span class="p">(</span><span class="n">fname</span><span class="p">,</span> <span class="n">delimiter</span><span class="o">=</span><span class="s1">','</span><span class="p">)[:,</span><span class="mi">1</span><span class="p">:]</span>
<span class="n">label</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">array</span><span class="p">([</span><span class="nb">ord</span><span class="p">(</span><span class="n">l</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s1">','</span><span class="p">)[</span><span class="mi">0</span><span class="p">])</span><span class="o">-</span><span class="nb">ord</span><span class="p">(</span><span class="s1">'A'</span><span class="p">)</span> <span class="k">for</span> <span class="n">l</span> <span class="ow">in</span> <span class="nb">open</span><span class="p">(</span><span class="n">fname</span><span class="p">,</span> <span class="s1">'r'</span><span class="p">)])</span>
<span class="n">batch_size</span> <span class="o">=</span> <span class="mi">32</span>
<span class="n">ntrain</span> <span class="o">=</span> <span class="nb">int</span><span class="p">(</span><span class="n">data</span><span class="o">.</span><span class="n">shape</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">*</span><span class="mf">0.8</span><span class="p">)</span>
<span class="n">train_iter</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">io</span><span class="o">.</span><span class="n">NDArrayIter</span><span class="p">(</span><span class="n">data</span><span class="p">[:</span><span class="n">ntrain</span><span class="p">,</span> <span class="p">:],</span> <span class="n">label</span><span class="p">[:</span><span class="n">ntrain</span><span class="p">],</span> <span class="n">batch_size</span><span class="p">,</span> <span class="n">shuffle</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">val_iter</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">io</span><span class="o">.</span><span class="n">NDArrayIter</span><span class="p">(</span><span class="n">data</span><span class="p">[</span><span class="n">ntrain</span><span class="p">:,</span> <span class="p">:],</span> <span class="n">label</span><span class="p">[</span><span class="n">ntrain</span><span class="p">:],</span> <span class="n">batch_size</span><span class="p">)</span>
</pre></div>
</div>
<p>Next, we define the network.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">net</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">sym</span><span class="o">.</span><span class="n">Variable</span><span class="p">(</span><span class="s1">'data'</span><span class="p">)</span>
<span class="n">net</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">sym</span><span class="o">.</span><span class="n">FullyConnected</span><span class="p">(</span><span class="n">net</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s1">'fc1'</span><span class="p">,</span> <span class="n">num_hidden</span><span class="o">=</span><span class="mi">64</span><span class="p">)</span>
<span class="n">net</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">sym</span><span class="o">.</span><span class="n">Activation</span><span class="p">(</span><span class="n">net</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s1">'relu1'</span><span class="p">,</span> <span class="n">act_type</span><span class="o">=</span><span class="s2">"relu"</span><span class="p">)</span>
<span class="n">net</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">sym</span><span class="o">.</span><span class="n">FullyConnected</span><span class="p">(</span><span class="n">net</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s1">'fc2'</span><span class="p">,</span> <span class="n">num_hidden</span><span class="o">=</span><span class="mi">26</span><span class="p">)</span>
<span class="n">net</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">sym</span><span class="o">.</span><span class="n">SoftmaxOutput</span><span class="p">(</span><span class="n">net</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s1">'softmax'</span><span class="p">)</span>
<span class="n">mx</span><span class="o">.</span><span class="n">viz</span><span class="o">.</span><span class="n">plot_network</span><span class="p">(</span><span class="n">net</span><span class="p">)</span>
</pre></div>
</div>
<p><img alt="svg" src="https://raw.githubusercontent.com/dmlc/web-data/master/mxnet/doc/tutorials/basic/module/output_3_0.svg?sanitize=true"/></p>
</div>
<div class="section" id="creating-a-module">
<span id="creating-a-module"></span><h2>Creating a Module<a class="headerlink" href="#creating-a-module" title="Permalink to this headline"></a></h2>
<p>Now we are ready to introduce module. The commonly used module class is
<code class="docutils literal"><span class="pre">Module</span></code>. We can construct a module by specifying the following parameters:</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">symbol</span></code>: the network definition</li>
<li><code class="docutils literal"><span class="pre">context</span></code>: the device (or a list of devices) to use for execution</li>
<li><code class="docutils literal"><span class="pre">data_names</span></code> : the list of input data variable names</li>
<li><code class="docutils literal"><span class="pre">label_names</span></code> : the list of input label variable names</li>
</ul>
<p>For <code class="docutils literal"><span class="pre">net</span></code>, we have only one data named <code class="docutils literal"><span class="pre">data</span></code>, and one label named <code class="docutils literal"><span class="pre">softmax_label</span></code>,
which is automatically named for us following the name <code class="docutils literal"><span class="pre">softmax</span></code> we specified for the <code class="docutils literal"><span class="pre">SoftmaxOutput</span></code> operator.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">mod</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">mod</span><span class="o">.</span><span class="n">Module</span><span class="p">(</span><span class="n">symbol</span><span class="o">=</span><span class="n">net</span><span class="p">,</span>
<span class="n">context</span><span class="o">=</span><span class="n">mx</span><span class="o">.</span><span class="n">cpu</span><span class="p">(),</span>
<span class="n">data_names</span><span class="o">=</span><span class="p">[</span><span class="s1">'data'</span><span class="p">],</span>
<span class="n">label_names</span><span class="o">=</span><span class="p">[</span><span class="s1">'softmax_label'</span><span class="p">])</span>
</pre></div>
</div>
</div>
<div class="section" id="intermediate-level-interface">
<span id="intermediate-level-interface"></span><h2>Intermediate-level Interface<a class="headerlink" href="#intermediate-level-interface" title="Permalink to this headline"></a></h2>
<p>We have created module. Now let us see how to run training and inference using module’s intermediate-level APIs. These APIs give developers flexibility to do step-by-step
computation by running <code class="docutils literal"><span class="pre">forward</span></code> and <code class="docutils literal"><span class="pre">backward</span></code> passes. It’s also useful for debugging.</p>
<p>To train a module, we need to perform following steps:</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">bind</span></code> : Prepares environment for the computation by allocating memory.</li>
<li><code class="docutils literal"><span class="pre">init_params</span></code> : Assigns and initializes parameters.</li>
<li><code class="docutils literal"><span class="pre">init_optimizer</span></code> : Initializes optimizers. Defaults to <code class="docutils literal"><span class="pre">sgd</span></code>.</li>
<li><code class="docutils literal"><span class="pre">metric.create</span></code> : Creates evaluation metric from input metric name.</li>
<li><code class="docutils literal"><span class="pre">forward</span></code> : Forward computation.</li>
<li><code class="docutils literal"><span class="pre">update_metric</span></code> : Evaluates and accumulates evaluation metric on outputs of the last forward computation.</li>
<li><code class="docutils literal"><span class="pre">backward</span></code> : Backward computation.</li>
<li><code class="docutils literal"><span class="pre">update</span></code> : Updates parameters according to the installed optimizer and the gradients computed in the previous forward-backward batch.</li>
</ul>
<p>This can be used as follows:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="c1"># allocate memory given the input data and label shapes</span>
<span class="n">mod</span><span class="o">.</span><span class="n">bind</span><span class="p">(</span><span class="n">data_shapes</span><span class="o">=</span><span class="n">train_iter</span><span class="o">.</span><span class="n">provide_data</span><span class="p">,</span> <span class="n">label_shapes</span><span class="o">=</span><span class="n">train_iter</span><span class="o">.</span><span class="n">provide_label</span><span class="p">)</span>
<span class="c1"># initialize parameters by uniform random numbers</span>
<span class="n">mod</span><span class="o">.</span><span class="n">init_params</span><span class="p">(</span><span class="n">initializer</span><span class="o">=</span><span class="n">mx</span><span class="o">.</span><span class="n">init</span><span class="o">.</span><span class="n">Uniform</span><span class="p">(</span><span class="n">scale</span><span class="o">=.</span><span class="mi">1</span><span class="p">))</span>
<span class="c1"># use SGD with learning rate 0.1 to train</span>
<span class="n">mod</span><span class="o">.</span><span class="n">init_optimizer</span><span class="p">(</span><span class="n">optimizer</span><span class="o">=</span><span class="s1">'sgd'</span><span class="p">,</span> <span class="n">optimizer_params</span><span class="o">=</span><span class="p">((</span><span class="s1">'learning_rate'</span><span class="p">,</span> <span class="mf">0.1</span><span class="p">),</span> <span class="p">))</span>
<span class="c1"># use accuracy as the metric</span>
<span class="n">metric</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">metric</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="s1">'acc'</span><span class="p">)</span>
<span class="c1"># train 5 epochs, i.e. going over the data iter one pass</span>
<span class="k">for</span> <span class="n">epoch</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">5</span><span class="p">):</span>
<span class="n">train_iter</span><span class="o">.</span><span class="n">reset</span><span class="p">()</span>
<span class="n">metric</span><span class="o">.</span><span class="n">reset</span><span class="p">()</span>
<span class="k">for</span> <span class="n">batch</span> <span class="ow">in</span> <span class="n">train_iter</span><span class="p">:</span>
<span class="n">mod</span><span class="o">.</span><span class="n">forward</span><span class="p">(</span><span class="n">batch</span><span class="p">,</span> <span class="n">is_train</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span> <span class="c1"># compute predictions</span>
<span class="n">mod</span><span class="o">.</span><span class="n">update_metric</span><span class="p">(</span><span class="n">metric</span><span class="p">,</span> <span class="n">batch</span><span class="o">.</span><span class="n">label</span><span class="p">)</span> <span class="c1"># accumulate prediction accuracy</span>
<span class="n">mod</span><span class="o">.</span><span class="n">backward</span><span class="p">()</span> <span class="c1"># compute gradients</span>
<span class="n">mod</span><span class="o">.</span><span class="n">update</span><span class="p">()</span> <span class="c1"># update parameters</span>
<span class="k">print</span><span class="p">(</span><span class="s1">'Epoch </span><span class="si">%d</span><span class="s1">, Training </span><span class="si">%s</span><span class="s1">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">epoch</span><span class="p">,</span> <span class="n">metric</span><span class="o">.</span><span class="n">get</span><span class="p">()))</span>
</pre></div>
</div>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">Epoch</span> <span class="mi">0</span><span class="p">,</span> <span class="n">Training</span> <span class="p">(</span><span class="s1">'accuracy'</span><span class="p">,</span> <span class="mf">0.4554375</span><span class="p">)</span>
<span class="n">Epoch</span> <span class="mi">1</span><span class="p">,</span> <span class="n">Training</span> <span class="p">(</span><span class="s1">'accuracy'</span><span class="p">,</span> <span class="mf">0.6485625</span><span class="p">)</span>
<span class="n">Epoch</span> <span class="mi">2</span><span class="p">,</span> <span class="n">Training</span> <span class="p">(</span><span class="s1">'accuracy'</span><span class="p">,</span> <span class="mf">0.7055625</span><span class="p">)</span>
<span class="n">Epoch</span> <span class="mi">3</span><span class="p">,</span> <span class="n">Training</span> <span class="p">(</span><span class="s1">'accuracy'</span><span class="p">,</span> <span class="mf">0.7396875</span><span class="p">)</span>
<span class="n">Epoch</span> <span class="mi">4</span><span class="p">,</span> <span class="n">Training</span> <span class="p">(</span><span class="s1">'accuracy'</span><span class="p">,</span> <span class="mf">0.764375</span><span class="p">)</span>
</pre></div>
</div>
<p>To learn more about these APIs, visit <a class="reference external" href="/versions/1.1.0/api/python/module/module.html">Module API</a>.</p>
</div>
<div class="section" id="high-level-interface">
<span id="high-level-interface"></span><h2>High-level Interface<a class="headerlink" href="#high-level-interface" title="Permalink to this headline"></a></h2>
<div class="section" id="train">
<span id="train"></span><h3>Train<a class="headerlink" href="#train" title="Permalink to this headline"></a></h3>
<p>Module also provides high-level APIs for training, predicting and evaluating for
user convenience. Instead of doing all the steps mentioned in the above section,
one can simply call <a class="reference external" href="/versions/1.1.0/api/python/module/module.html#mxnet.module.BaseModule.fit">fit API</a>
and it internally executes the same steps.</p>
<p>To fit a module, call the <code class="docutils literal"><span class="pre">fit</span></code> function as follows:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="c1"># reset train_iter to the beginning</span>
<span class="n">train_iter</span><span class="o">.</span><span class="n">reset</span><span class="p">()</span>
<span class="c1"># create a module</span>
<span class="n">mod</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">mod</span><span class="o">.</span><span class="n">Module</span><span class="p">(</span><span class="n">symbol</span><span class="o">=</span><span class="n">net</span><span class="p">,</span>
<span class="n">context</span><span class="o">=</span><span class="n">mx</span><span class="o">.</span><span class="n">cpu</span><span class="p">(),</span>
<span class="n">data_names</span><span class="o">=</span><span class="p">[</span><span class="s1">'data'</span><span class="p">],</span>
<span class="n">label_names</span><span class="o">=</span><span class="p">[</span><span class="s1">'softmax_label'</span><span class="p">])</span>
<span class="c1"># fit the module</span>
<span class="n">mod</span><span class="o">.</span><span class="n">fit</span><span class="p">(</span><span class="n">train_iter</span><span class="p">,</span>
<span class="n">eval_data</span><span class="o">=</span><span class="n">val_iter</span><span class="p">,</span>
<span class="n">optimizer</span><span class="o">=</span><span class="s1">'sgd'</span><span class="p">,</span>
<span class="n">optimizer_params</span><span class="o">=</span><span class="p">{</span><span class="s1">'learning_rate'</span><span class="p">:</span><span class="mf">0.1</span><span class="p">},</span>
<span class="n">eval_metric</span><span class="o">=</span><span class="s1">'acc'</span><span class="p">,</span>
<span class="n">num_epoch</span><span class="o">=</span><span class="mi">8</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.364625</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.388</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="n">Validation</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.557250</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.633625</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.470</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="n">Validation</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.634750</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.697187</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.402</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="n">Validation</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.665500</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.735062</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.402</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="n">Validation</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.713000</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.762563</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.408</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="n">Validation</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.742000</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.782312</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.400</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span> <span class="n">Validation</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.778500</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">6</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.797188</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">6</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.392</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">6</span><span class="p">]</span> <span class="n">Validation</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.798250</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">7</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.807750</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">7</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.401</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">7</span><span class="p">]</span> <span class="n">Validation</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.789250</span>
</pre></div>
</div>
<p>By default, <code class="docutils literal"><span class="pre">fit</span></code> function has <code class="docutils literal"><span class="pre">eval_metric</span></code> set to <code class="docutils literal"><span class="pre">accuracy</span></code>, <code class="docutils literal"><span class="pre">optimizer</span></code> to <code class="docutils literal"><span class="pre">sgd</span></code>
and optimizer_params to <code class="docutils literal"><span class="pre">(('learning_rate',</span> <span class="pre">0.01),)</span></code>.</p>
</div>
<div class="section" id="predict-and-evaluate">
<span id="predict-and-evaluate"></span><h3>Predict and Evaluate<a class="headerlink" href="#predict-and-evaluate" title="Permalink to this headline"></a></h3>
<p>To predict with module, we can call <code class="docutils literal"><span class="pre">predict()</span></code>. It will collect and
return all the prediction results.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">y</span> <span class="o">=</span> <span class="n">mod</span><span class="o">.</span><span class="n">predict</span><span class="p">(</span><span class="n">val_iter</span><span class="p">)</span>
<span class="k">assert</span> <span class="n">y</span><span class="o">.</span><span class="n">shape</span> <span class="o">==</span> <span class="p">(</span><span class="mi">4000</span><span class="p">,</span> <span class="mi">26</span><span class="p">)</span>
</pre></div>
</div>
<p>If we do not need the prediction outputs, but just need to evaluate on a test
set, we can call the <code class="docutils literal"><span class="pre">score()</span></code> function. It runs prediction in the input validation
dataset and evaluates the performance according to the given input metric.</p>
<p>It can be used as follows:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">score</span> <span class="o">=</span> <span class="n">mod</span><span class="o">.</span><span class="n">score</span><span class="p">(</span><span class="n">val_iter</span><span class="p">,</span> <span class="p">[</span><span class="s1">'acc'</span><span class="p">])</span>
<span class="k">print</span><span class="p">(</span><span class="s2">"Accuracy score is </span><span class="si">%f</span><span class="s2">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">score</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="mi">1</span><span class="p">]))</span>
<span class="k">assert</span> <span class="n">score</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="mi">1</span><span class="p">]</span> <span class="o">></span> <span class="mf">0.77</span><span class="p">,</span> <span class="s2">"Achieved accuracy (</span><span class="si">%f</span><span class="s2">) is less than expected (0.77)"</span> <span class="o">%</span> <span class="n">score</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="mi">1</span><span class="p">]</span>
</pre></div>
</div>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">Accuracy</span> <span class="n">score</span> <span class="ow">is</span> <span class="mf">0.789250</span>
</pre></div>
</div>
<p>Some of the other metrics which can be used are <code class="docutils literal"><span class="pre">top_k_acc</span></code>(top-k-accuracy),
<code class="docutils literal"><span class="pre">F1</span></code>, <code class="docutils literal"><span class="pre">RMSE</span></code>, <code class="docutils literal"><span class="pre">MSE</span></code>, <code class="docutils literal"><span class="pre">MAE</span></code>, <code class="docutils literal"><span class="pre">ce</span></code>(CrossEntropy). To learn more about the metrics,
visit <a class="reference external" href="/versions/1.1.0/api/python/metric/metric.html">Evaluation metric</a>.</p>
<p>One can vary number of epochs, learning_rate, optimizer parameters to change the score
and tune these parameters to get best score.</p>
</div>
<div class="section" id="save-and-load">
<span id="save-and-load"></span><h3>Save and Load<a class="headerlink" href="#save-and-load" title="Permalink to this headline"></a></h3>
<p>We can save the module parameters after each training epoch by using a checkpoint callback.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="c1"># construct a callback function to save checkpoints</span>
<span class="n">model_prefix</span> <span class="o">=</span> <span class="s1">'mx_mlp'</span>
<span class="n">checkpoint</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">callback</span><span class="o">.</span><span class="n">do_checkpoint</span><span class="p">(</span><span class="n">model_prefix</span><span class="p">)</span>
<span class="n">mod</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">mod</span><span class="o">.</span><span class="n">Module</span><span class="p">(</span><span class="n">symbol</span><span class="o">=</span><span class="n">net</span><span class="p">)</span>
<span class="n">mod</span><span class="o">.</span><span class="n">fit</span><span class="p">(</span><span class="n">train_iter</span><span class="p">,</span> <span class="n">num_epoch</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span> <span class="n">epoch_end_callback</span><span class="o">=</span><span class="n">checkpoint</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.101062</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.422</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Saved</span> <span class="n">checkpoint</span> <span class="n">to</span> <span class="s2">"mx_mlp-0001.params"</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.263313</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.785</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Saved</span> <span class="n">checkpoint</span> <span class="n">to</span> <span class="s2">"mx_mlp-0002.params"</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.452188</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.624</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Saved</span> <span class="n">checkpoint</span> <span class="n">to</span> <span class="s2">"mx_mlp-0003.params"</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.544125</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.427</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Saved</span> <span class="n">checkpoint</span> <span class="n">to</span> <span class="s2">"mx_mlp-0004.params"</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.605250</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.399</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Saved</span> <span class="n">checkpoint</span> <span class="n">to</span> <span class="s2">"mx_mlp-0005.params"</span>
</pre></div>
</div>
<p>To load the saved module parameters, call the <code class="docutils literal"><span class="pre">load_checkpoint</span></code> function. It
loads the Symbol and the associated parameters. We can then set the loaded
parameters into the module.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">sym</span><span class="p">,</span> <span class="n">arg_params</span><span class="p">,</span> <span class="n">aux_params</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">model</span><span class="o">.</span><span class="n">load_checkpoint</span><span class="p">(</span><span class="n">model_prefix</span><span class="p">,</span> <span class="mi">3</span><span class="p">)</span>
<span class="k">assert</span> <span class="n">sym</span><span class="o">.</span><span class="n">tojson</span><span class="p">()</span> <span class="o">==</span> <span class="n">net</span><span class="o">.</span><span class="n">tojson</span><span class="p">()</span>
<span class="c1"># assign the loaded parameters to the module</span>
<span class="n">mod</span><span class="o">.</span><span class="n">set_params</span><span class="p">(</span><span class="n">arg_params</span><span class="p">,</span> <span class="n">aux_params</span><span class="p">)</span>
</pre></div>
</div>
<p>Or if we just want to resume training from a saved checkpoint, instead of
calling <code class="docutils literal"><span class="pre">set_params()</span></code>, we can directly call <code class="docutils literal"><span class="pre">fit()</span></code>, passing the loaded
parameters, so that <code class="docutils literal"><span class="pre">fit()</span></code> knows to start from those parameters instead of
initializing randomly from scratch. We also set the <code class="docutils literal"><span class="pre">begin_epoch</span></code> parameter so that
<code class="docutils literal"><span class="pre">fit()</span></code> knows we are resuming from a previously saved epoch.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">mod</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">mod</span><span class="o">.</span><span class="n">Module</span><span class="p">(</span><span class="n">symbol</span><span class="o">=</span><span class="n">sym</span><span class="p">)</span>
<span class="n">mod</span><span class="o">.</span><span class="n">fit</span><span class="p">(</span><span class="n">train_iter</span><span class="p">,</span>
<span class="n">num_epoch</span><span class="o">=</span><span class="mi">21</span><span class="p">,</span>
<span class="n">arg_params</span><span class="o">=</span><span class="n">arg_params</span><span class="p">,</span>
<span class="n">aux_params</span><span class="o">=</span><span class="n">aux_params</span><span class="p">,</span>
<span class="n">begin_epoch</span><span class="o">=</span><span class="mi">3</span><span class="p">)</span>
<span class="k">assert</span> <span class="n">score</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="mi">1</span><span class="p">]</span> <span class="o">></span> <span class="mf">0.77</span><span class="p">,</span> <span class="s2">"Achieved accuracy (</span><span class="si">%f</span><span class="s2">) is less than expected (0.77)"</span> <span class="o">%</span> <span class="n">score</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="mi">1</span><span class="p">]</span>
</pre></div>
</div>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.544125</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.398</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.605250</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.545</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.644312</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.592</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">6</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.675000</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">6</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.491</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">7</span><span class="p">]</span> <span class="n">Train</span><span class="o">-</span><span class="n">accuracy</span><span class="o">=</span><span class="mf">0.695812</span>
<span class="n">INFO</span><span class="p">:</span><span class="n">root</span><span class="p">:</span><span class="n">Epoch</span><span class="p">[</span><span class="mi">7</span><span class="p">]</span> <span class="n">Time</span> <span class="n">cost</span><span class="o">=</span><span class="mf">0.363</span>
</pre></div>
</div>
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<h3><a href="../../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Module - Neural network training and inference</a><ul>
<li><a class="reference internal" href="#prerequisites">Prerequisites</a></li>
<li><a class="reference internal" href="#preliminary">Preliminary</a></li>
<li><a class="reference internal" href="#creating-a-module">Creating a Module</a></li>
<li><a class="reference internal" href="#intermediate-level-interface">Intermediate-level Interface</a></li>
<li><a class="reference internal" href="#high-level-interface">High-level Interface</a><ul>
<li><a class="reference internal" href="#train">Train</a></li>
<li><a class="reference internal" href="#predict-and-evaluate">Predict and Evaluate</a></li>
<li><a class="reference internal" href="#save-and-load">Save and Load</a></li>
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