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<h1>Source code for torchreid.optim.lr_scheduler</h1><div class="highlight"><pre>
<span></span><span class="kn">from</span> <span class="nn">__future__</span> <span class="k">import</span> <span class="n">absolute_import</span>
<span class="kn">from</span> <span class="nn">__future__</span> <span class="k">import</span> <span class="n">print_function</span>
<span class="kn">import</span> <span class="nn">torch</span>
<span class="n">AVAI_SCH</span> <span class="o">=</span> <span class="p">[</span><span class="s1">&#39;single_step&#39;</span><span class="p">,</span> <span class="s1">&#39;multi_step&#39;</span><span class="p">]</span>
<div class="viewcode-block" id="build_lr_scheduler"><a class="viewcode-back" href="../../../pkg/optim.html#torchreid.optim.lr_scheduler.build_lr_scheduler">[docs]</a><span class="k">def</span> <span class="nf">build_lr_scheduler</span><span class="p">(</span><span class="n">optimizer</span><span class="p">,</span> <span class="n">lr_scheduler</span><span class="p">,</span> <span class="n">stepsize</span><span class="p">,</span> <span class="n">gamma</span><span class="o">=</span><span class="mf">0.1</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;A function wrapper for building a learning rate scheduler.</span>
<span class="sd"> Args:</span>
<span class="sd"> optimizer (Optimizer): an Optimizer.</span>
<span class="sd"> lr_scheduler (str): learning rate scheduler method. Currently supports</span>
<span class="sd"> &quot;single_step&quot; and &quot;multi_step&quot;.</span>
<span class="sd"> stepsize (int or list): step size to decay learning rate. When ``lr_scheduler`` is</span>
<span class="sd"> &quot;single_step&quot;, ``stepsize`` should be an integer. When ``lr_scheduler`` is</span>
<span class="sd"> &quot;multi_step&quot;, ``stepsize`` is a list.</span>
<span class="sd"> gamma (float, optional): decay rate. Default is 0.1.</span>
<span class="sd"> Examples::</span>
<span class="sd"> &gt;&gt;&gt; # Decay learning rate by every 20 epochs.</span>
<span class="sd"> &gt;&gt;&gt; scheduler = torchreid.optim.build_lr_scheduler(</span>
<span class="sd"> &gt;&gt;&gt; optimizer, lr_scheduler=&#39;single_step&#39;, stepsize=20</span>
<span class="sd"> &gt;&gt;&gt; )</span>
<span class="sd"> &gt;&gt;&gt; # Decay learning rate at 30, 50 and 55 epochs.</span>
<span class="sd"> &gt;&gt;&gt; scheduler = torchreid.optim.build_lr_scheduler(</span>
<span class="sd"> &gt;&gt;&gt; optimizer, lr_scheduler=&#39;multi_step&#39;, stepsize=[30, 50, 55]</span>
<span class="sd"> &gt;&gt;&gt; )</span>
<span class="sd"> &quot;&quot;&quot;</span>
<span class="k">if</span> <span class="n">lr_scheduler</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">AVAI_SCH</span><span class="p">:</span>
<span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span><span class="s1">&#39;Unsupported scheduler: </span><span class="si">{}</span><span class="s1">. Must be one of </span><span class="si">{}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">lr_scheduler</span><span class="p">,</span> <span class="n">AVAI_SCH</span><span class="p">))</span>
<span class="nb">print</span><span class="p">(</span><span class="s1">&#39;Initializing lr_scheduler: </span><span class="si">{}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">lr_scheduler</span><span class="p">))</span>
<span class="k">if</span> <span class="n">lr_scheduler</span> <span class="o">==</span> <span class="s1">&#39;single_step&#39;</span><span class="p">:</span>
<span class="k">if</span> <span class="ow">not</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">stepsize</span><span class="p">,</span> <span class="nb">int</span><span class="p">):</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span>
<span class="s1">&#39;For single_step lr_scheduler, stepsize must &#39;</span>
<span class="s1">&#39;be an integer, but got </span><span class="si">{}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="nb">type</span><span class="p">(</span><span class="n">stepsize</span><span class="p">))</span>
<span class="p">)</span>
<span class="n">scheduler</span> <span class="o">=</span> <span class="n">torch</span><span class="o">.</span><span class="n">optim</span><span class="o">.</span><span class="n">lr_scheduler</span><span class="o">.</span><span class="n">StepLR</span><span class="p">(</span>
<span class="n">optimizer</span><span class="p">,</span> <span class="n">step_size</span><span class="o">=</span><span class="n">stepsize</span><span class="p">,</span> <span class="n">gamma</span><span class="o">=</span><span class="n">gamma</span>
<span class="p">)</span>
<span class="k">elif</span> <span class="n">lr_scheduler</span> <span class="o">==</span> <span class="s1">&#39;multi_step&#39;</span><span class="p">:</span>
<span class="k">if</span> <span class="ow">not</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">stepsize</span><span class="p">,</span> <span class="nb">list</span><span class="p">):</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span>
<span class="s1">&#39;For multi_step lr_scheduler, stepsize must &#39;</span>
<span class="s1">&#39;be a list, but got </span><span class="si">{}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="nb">type</span><span class="p">(</span><span class="n">stepsize</span><span class="p">))</span>
<span class="p">)</span>
<span class="n">scheduler</span> <span class="o">=</span> <span class="n">torch</span><span class="o">.</span><span class="n">optim</span><span class="o">.</span><span class="n">lr_scheduler</span><span class="o">.</span><span class="n">MultiStepLR</span><span class="p">(</span>
<span class="n">optimizer</span><span class="p">,</span> <span class="n">milestones</span><span class="o">=</span><span class="n">stepsize</span><span class="p">,</span> <span class="n">gamma</span><span class="o">=</span><span class="n">gamma</span>
<span class="p">)</span>
<span class="k">return</span> <span class="n">scheduler</span></div>
</pre></div>
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