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<h1>前 k 个采样</h1>
<p>在这里我们首先从logits分布中挑选top-k代币然后从中采样。</p>
<p>这是一个使用这些采样技术的<a href="experiment.html">实验</a></p>
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<div class="highlight"><pre><span class="lineno">15</span><span></span><span class="kn">import</span> <span class="nn">torch</span>
<span class="lineno">16</span>
<span class="lineno">17</span><span class="kn">from</span> <span class="nn">labml_nn.sampling</span> <span class="kn">import</span> <span class="n">Sampler</span></pre></div>
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<h2>Top-k 采样器</h2>
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<div class="highlight"><pre><span class="lineno">20</span><span class="k">class</span> <span class="nc">TopKSampler</span><span class="p">(</span><span class="n">Sampler</span><span class="p">):</span></pre></div>
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<ul><li><code class="highlight"><span></span><span class="n">k</span></code>
是要挑选的代币数量</li>
<li><code class="highlight"><span></span><span class="n">sampler</span></code>
是用于前 k 个代币的采样器</li></ul>
<p><code class="highlight"><span></span><span class="n">sampler</span></code>
可以是任何以 logits 张量作为输入并返回令牌张量的采样器;例如 <a href="temperature.html">“TemperatureSample”</a></p>
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<div class="highlight"><pre><span class="lineno">24</span> <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">k</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">sampler</span><span class="p">:</span> <span class="n">Sampler</span><span class="p">):</span></pre></div>
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<div class="highlight"><pre><span class="lineno">32</span> <span class="bp">self</span><span class="o">.</span><span class="n">k</span> <span class="o">=</span> <span class="n">k</span>
<span class="lineno">33</span> <span class="bp">self</span><span class="o">.</span><span class="n">sampler</span> <span class="o">=</span> <span class="n">sampler</span></pre></div>
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<p>来自 logits 的样本</p>
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<div class="highlight"><pre><span class="lineno">35</span> <span class="k">def</span> <span class="fm">__call__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">logits</span><span class="p">:</span> <span class="n">torch</span><span class="o">.</span><span class="n">Tensor</span><span class="p">):</span></pre></div>
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<p>新的 logit 填充了<span ><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.66666em;vertical-align:-0.08333em;"></span><span class="mord coloredeq eqa" style=""><span class="mord" style=""></span><span class="mord" style=""></span></span></span></span></span></span>;即零概率</p>
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<div class="highlight"><pre><span class="lineno">40</span> <span class="n">zeros</span> <span class="o">=</span> <span class="n">logits</span><span class="o">.</span><span class="n">new_ones</span><span class="p">(</span><span class="n">logits</span><span class="o">.</span><span class="n">shape</span><span class="p">)</span> <span class="o">*</span> <span class="nb">float</span><span class="p">(</span><span class="s1">&#39;-inf&#39;</span><span class="p">)</span></pre></div>
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<p>选择最大的对<span ><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.69444em;vertical-align:0em;"></span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span></span></span></span></span>数及其指数</p>
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<div class="highlight"><pre><span class="lineno">42</span> <span class="n">values</span><span class="p">,</span> <span class="n">indices</span> <span class="o">=</span> <span class="n">torch</span><span class="o">.</span><span class="n">topk</span><span class="p">(</span><span class="n">logits</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">k</span><span class="p">,</span> <span class="n">dim</span><span class="o">=-</span><span class="mi">1</span><span class="p">)</span></pre></div>
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<p>将选定前 k 个索引的值设置为实际对数。其他代币的记录仍然存在<span ><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.66666em;vertical-align:-0.08333em;"></span><span class="mord coloredeq eqa" style=""><span class="mord" style=""></span><span class="mord" style=""></span></span></span></span></span></span></p>
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<div class="highlight"><pre><span class="lineno">45</span> <span class="n">zeros</span><span class="o">.</span><span class="n">scatter_</span><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="n">indices</span><span class="p">,</span> <span class="n">values</span><span class="p">)</span></pre></div>
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<p>使用指定采样器从 top-k logits 中抽样。</p>
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<div class="highlight"><pre><span class="lineno">48</span> <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">sampler</span><span class="p">(</span><span class="n">zeros</span><span class="p">)</span></pre></div>
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