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            <h1>Pay Attention to MLPs (gMLP)</h1>
<p>This is a <a href="https://pytorch.org">PyTorch</a> implementation of the paper <a href="https://papers.labml.ai/paper/2105.08050">Pay Attention to MLPs</a>.</p>
<p>This paper introduces a Multilayer Perceptron (MLP) based architecture with gating, which they name <strong>gMLP</strong>. It consists of a stack of <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord mathnormal">L</span></span></span></span> <em>gMLP</em> blocks.</p>
<p>Here is <a href="experiment.html">the training code</a> for a gMLP model based autoregressive model.</p>
<p><a href="https://app.labml.ai/run/01bd941ac74c11eb890c1d9196651a4a"><img alt="View Run" src="https://img.shields.io/badge/labml-experiment-brightgreen"></a></p>

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            <div class="highlight"><pre><span class="lineno">21</span><span></span><span class="kn">from</span> <span class="nn">typing</span> <span class="kn">import</span> <span class="n">Optional</span>
<span class="lineno">22</span>
<span class="lineno">23</span><span class="kn">import</span> <span class="nn">torch</span>
<span class="lineno">24</span><span class="kn">from</span> <span class="nn">torch</span> <span class="kn">import</span> <span class="n">nn</span></pre></div>
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            <h2>gMLP Block</h2>
<p>Each block does the following transformations to input embeddings <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.72243em;vertical-align:-0.0391em;"></span><span class="mord coloredeq eqx" style=""><span class="mord mathnormal" style="margin-right:0.07847em">X</span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">∈</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.8491079999999999em;vertical-align:0em;"></span><span class="mord"><span class="mord mathbb">R</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8491079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight coloredeq eqbc" style=""><span class="mord mathnormal mtight" style="">n</span></span><span class="mbin mtight">×</span><span class="mord mtight coloredeq eqba" style=""><span class="mord mathnormal mtight" style="">d</span></span></span></span></span></span></span></span></span></span></span></span></span> where <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.43056em;vertical-align:0em;"></span><span class="mord coloredeq eqbc" style=""><span class="mord mathnormal" style="">n</span></span></span></span></span> is the sequence length and <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 coloredeq eqba" style=""><span class="mord mathnormal" style="">d</span></span></span></span></span> is the dimensionality of the embeddings:</p>
<span class="katex-display"><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:4.66038em;vertical-align:-2.08019em;"></span><span class="mord"><span class="mtable"><span class="col-align-r"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:2.58019em;"><span style="top:-4.74019em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span></span><span style="top:-3.16em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord accent"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.9201899999999998em;"><span style="top:-3em;"><span class="pstrut" style="height:3em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span><span style="top:-3.6023300000000003em;"><span class="pstrut" style="height:3em;"></span><span class="accent-body" style="left:-0.16666em;"><span class="mord">~</span></span></span></span></span></span></span></span></span><span style="top:-1.5798100000000002em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.22222em;">Y</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:2.08019em;"><span></span></span></span></span></span><span class="col-align-l"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:2.58019em;"><span style="top:-4.74019em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord"></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mord coloredeq eqn" style=""><span class="mord mathnormal" style="margin-right:0.03588em">σ</span></span><span class="mopen">(</span><span class="mord coloredeq eqx" style=""><span class="mord mathnormal" style="margin-right:0.07847em">X</span></span><span class="mord coloredeq equ" style=""><span class="mord mathnormal" style="margin-right:0.10903em">U</span></span><span class="mclose">)</span></span></span><span style="top:-3.16em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord"></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mord mathnormal">s</span><span class="mopen">(</span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="mclose">)</span></span></span><span style="top:-1.5798100000000002em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord"></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mord accent"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.9201899999999998em;"><span style="top:-3em;"><span class="pstrut" style="height:3em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span><span style="top:-3.6023300000000003em;"><span class="pstrut" style="height:3em;"></span><span class="accent-body" style="left:-0.16666em;"><span class="mord">~</span></span></span></span></span></span></span><span class="mord coloredeq eqv" style=""><span class="mord mathnormal" style="margin-right:0.22222em">V</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:2.08019em;"><span></span></span></span></span></span></span></span></span></span></span></span><p>where <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqv" style=""><span class="mord mathnormal" style="margin-right:0.22222em">V</span></span></span></span></span> and <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq equ" style=""><span class="mord mathnormal" style="margin-right:0.10903em">U</span></span></span></span></span> are learnable projection weights. <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">s</span><span class="mopen">(</span><span class="mord">⋅</span><span class="mclose">)</span></span></span></span> is the Spacial Gating Unit defined below. Output dimensionality of <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">s</span><span class="mopen">(</span><span class="mord">⋅</span><span class="mclose">)</span></span></span></span> will be half of <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span></span></span>. <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.43056em;vertical-align:0em;"></span><span class="mord coloredeq eqn" style=""><span class="mord mathnormal" style="margin-right:0.03588em">σ</span></span></span></span></span> is an activation function such as <a href="https://pytorch.org/docs/stable/generated/torch.nn.GELU.html">GeLU</a>.</p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">27</span><span class="k">class</span> <span class="nc">GMLPBlock</span><span class="p">(</span><span class="n">nn</span><span class="o">.</span><span class="n">Module</span><span class="p">):</span></pre></div>
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            <ul><li><code class="highlight"><span></span><span class="n">d_model</span></code>
 is the dimensionality (<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 coloredeq eqba" style=""><span class="mord mathnormal" style="">d</span></span></span></span></span>) of <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqx" style=""><span class="mord mathnormal" style="margin-right:0.07847em">X</span></span></span></span></span> </li>
<li><code class="highlight"><span></span><span class="n">d_ffn</span></code>
 is the dimensionality of <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span></span></span> </li>
<li><code class="highlight"><span></span><span class="n">seq_len</span></code>
 is the length of the token sequence (<span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.43056em;vertical-align:0em;"></span><span class="mord coloredeq eqbc" style=""><span class="mord mathnormal" style="">n</span></span></span></span></span>)</li></ul>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">48</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">d_model</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">d_ffn</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">seq_len</span><span class="p">:</span> <span class="nb">int</span><span class="p">):</span></pre></div>
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            <div class="highlight"><pre><span class="lineno">54</span>        <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span></pre></div>
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            <p>Normalization layer fro Pre-Norm </p>

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            <div class="highlight"><pre><span class="lineno">56</span>        <span class="bp">self</span><span class="o">.</span><span class="n">norm</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">LayerNorm</span><span class="p">([</span><span class="n">d_model</span><span class="p">])</span></pre></div>
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            <p>Activation function <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.43056em;vertical-align:0em;"></span><span class="mord coloredeq eqn" style=""><span class="mord mathnormal" style="margin-right:0.03588em">σ</span></span></span></span></span> </p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">58</span>        <span class="bp">self</span><span class="o">.</span><span class="n">activation</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">GELU</span><span class="p">()</span></pre></div>
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            <p>Projection layer for <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord coloredeq eqn" style=""><span class="mord mathnormal" style="margin-right:0.03588em">σ</span></span><span class="mopen">(</span><span class="mord coloredeq eqx" style=""><span class="mord mathnormal" style="margin-right:0.07847em">X</span></span><span class="mord coloredeq equ" style=""><span class="mord mathnormal" style="margin-right:0.10903em">U</span></span><span class="mclose">)</span></span></span></span> </p>

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            <div class="highlight"><pre><span class="lineno">60</span>        <span class="bp">self</span><span class="o">.</span><span class="n">proj1</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Linear</span><span class="p">(</span><span class="n">d_model</span><span class="p">,</span> <span class="n">d_ffn</span><span class="p">)</span></pre></div>
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            <p>Spacial Gating Unit <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">s</span><span class="mopen">(</span><span class="mord">⋅</span><span class="mclose">)</span></span></span></span> </p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">62</span>        <span class="bp">self</span><span class="o">.</span><span class="n">sgu</span> <span class="o">=</span> <span class="n">SpacialGatingUnit</span><span class="p">(</span><span class="n">d_ffn</span><span class="p">,</span> <span class="n">seq_len</span><span class="p">)</span></pre></div>
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            <p>Projection layer for <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord mathnormal" style="margin-right:0.22222em;">Y</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.9201899999999998em;vertical-align:0em;"></span><span class="mord accent"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.9201899999999998em;"><span style="top:-3em;"><span class="pstrut" style="height:3em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span><span style="top:-3.6023300000000003em;"><span class="pstrut" style="height:3em;"></span><span class="accent-body" style="left:-0.16666em;"><span class="mord">~</span></span></span></span></span></span></span><span class="mord coloredeq eqv" style=""><span class="mord mathnormal" style="margin-right:0.22222em">V</span></span></span></span></span> </p>

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            <div class="highlight"><pre><span class="lineno">64</span>        <span class="bp">self</span><span class="o">.</span><span class="n">proj2</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Linear</span><span class="p">(</span><span class="n">d_ffn</span> <span class="o">//</span> <span class="mi">2</span><span class="p">,</span> <span class="n">d_model</span><span class="p">)</span></pre></div>
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            <p>Embedding size (required by <a href="../models.html#Encoder">Encoder</a>. We use the encoder module from transformer architecture and plug <em>gMLP</em> block as a replacement for the <a href="../models.html#Encoder">Transformer Layer</a>. </p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">68</span>        <span class="bp">self</span><span class="o">.</span><span class="n">size</span> <span class="o">=</span> <span class="n">d_model</span></pre></div>
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            <ul><li><code class="highlight"><span></span><span class="n">x</span></code>
 is the input embedding tensor <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqx" style=""><span class="mord mathnormal" style="margin-right:0.07847em">X</span></span></span></span></span> of shape <code class="highlight"><span></span><span class="p">[</span><span class="n">seq_len</span><span class="p">,</span> <span class="n">batch_size</span><span class="p">,</span> <span class="n">d_model</span><span class="p">]</span></code>
 </li>
<li><code class="highlight"><span></span><span class="n">mask</span></code>
 is a boolean mask of shape <code class="highlight"><span></span><span class="p">[</span><span class="n">seq_len</span><span class="p">,</span> <span class="n">seq_len</span><span class="p">,</span> <span class="mi">1</span><span class="p">]</span></code>
 that controls the visibility of tokens  among each other.</li></ul>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">70</span>    <span class="k">def</span> <span class="nf">forward</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">x</span><span class="p">:</span> <span class="n">torch</span><span class="o">.</span><span class="n">Tensor</span><span class="p">,</span> <span class="n">mask</span><span class="p">:</span> <span class="n">Optional</span><span class="p">[</span><span class="n">torch</span><span class="o">.</span><span class="n">Tensor</span><span class="p">]</span> <span class="o">=</span> <span class="kc">None</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-11'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-11'>#</a>
            </div>
            <p>Keep a copy for shortcut connection </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">77</span>        <span class="n">shortcut</span> <span class="o">=</span> <span class="n">x</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-12'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-12'>#</a>
            </div>
            <p>Normalize <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqx" style=""><span class="mord mathnormal" style="margin-right:0.07847em">X</span></span></span></span></span> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">79</span>        <span class="n">x</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">norm</span><span class="p">(</span><span class="n">x</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-13'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-13'>#</a>
            </div>
            <p>Projection and activation <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord coloredeq eqn" style=""><span class="mord mathnormal" style="margin-right:0.03588em">σ</span></span><span class="mopen">(</span><span class="mord coloredeq eqx" style=""><span class="mord mathnormal" style="margin-right:0.07847em">X</span></span><span class="mord coloredeq equ" style=""><span class="mord mathnormal" style="margin-right:0.10903em">U</span></span><span class="mclose">)</span></span></span></span> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">81</span>        <span class="n">z</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">activation</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">proj1</span><span class="p">(</span><span class="n">x</span><span class="p">))</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-14'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-14'>#</a>
            </div>
            <p>Spacial Gating Unit <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.9201899999999998em;vertical-align:0em;"></span><span class="mord accent"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.9201899999999998em;"><span style="top:-3em;"><span class="pstrut" style="height:3em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span><span style="top:-3.6023300000000003em;"><span class="pstrut" style="height:3em;"></span><span class="accent-body" style="left:-0.16666em;"><span class="mord">~</span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">s</span><span class="mopen">(</span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="mclose">)</span></span></span></span> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">83</span>        <span class="n">z</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">sgu</span><span class="p">(</span><span class="n">z</span><span class="p">,</span> <span class="n">mask</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-15'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-15'>#</a>
            </div>
            <p>Final projection <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord mathnormal" style="margin-right:0.22222em;">Y</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.9201899999999998em;vertical-align:0em;"></span><span class="mord accent"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.9201899999999998em;"><span style="top:-3em;"><span class="pstrut" style="height:3em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span><span style="top:-3.6023300000000003em;"><span class="pstrut" style="height:3em;"></span><span class="accent-body" style="left:-0.16666em;"><span class="mord">~</span></span></span></span></span></span></span><span class="mord coloredeq eqv" style=""><span class="mord mathnormal" style="margin-right:0.22222em">V</span></span></span></span></span> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">85</span>        <span class="n">z</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">proj2</span><span class="p">(</span><span class="n">z</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-16'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-16'>#</a>
            </div>
            <p>Add the shortcut connection </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">88</span>        <span class="k">return</span> <span class="n">z</span> <span class="o">+</span> <span class="n">shortcut</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-17'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-17'>#</a>
            </div>
            <h2>Spatial Gating Unit</h2>
<p><span class="katex-display"><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">s</span><span class="mopen">(</span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1.036108em;vertical-align:-0.286108em;"></span><span class="mord coloredeq eqe" style=""><span class="mord coloredeq eqp" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight coloredeq eqs" style=""><span class="mord mtight" style="">1</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span><span class="mord coloredeq eqo" style=""><span class="mord" style="">⊙</span></span><span class="mord" style=""><span class="mord mathnormal" style="margin-right:0.10764em">f</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3361079999999999em;"><span style="top:-2.5500000000000003em;margin-left:-0.10764em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style=""><span class="mord mtight coloredeq eqw" style=""><span class="mord mathnormal mtight" style="margin-right:0.13889em">W</span></span><span class="mpunct mtight" style="">,</span><span class="mord mtight coloredeq eqz" style=""><span class="mord mathnormal mtight" style="">b</span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.286108em;"><span></span></span></span></span></span></span><span class="mopen" style="">(</span><span class="mord coloredeq eqq" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style="">2</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span><span class="mclose" style="">)</span></span></span></span></span></span></p>
<p>where <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1.036108em;vertical-align:-0.286108em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3361079999999999em;"><span style="top:-2.5500000000000003em;margin-left:-0.10764em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight coloredeq eqw" style=""><span class="mord mathnormal mtight" style="margin-right:0.13889em">W</span></span><span class="mpunct mtight">,</span><span class="mord mtight coloredeq eqz" style=""><span class="mord mathnormal mtight" style="">b</span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.286108em;"><span></span></span></span></span></span></span><span class="mopen">(</span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.76666em;vertical-align:-0.08333em;"></span><span class="mord coloredeq eqw" style=""><span class="mord mathnormal" style="margin-right:0.13889em">W</span></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.69444em;vertical-align:0em;"></span><span class="mord coloredeq eqz" style=""><span class="mord mathnormal" style="">b</span></span></span></span></span> is a linear transformation along the sequence dimension, and <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 eqo" style=""><span class="mord" style="">⊙</span></span></span></span></span> is element-wise multiplication. <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span></span></span> is split into to parts of equal size <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.83333em;vertical-align:-0.15em;"></span><span class="mord coloredeq eqp" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight coloredeq eqs" style=""><span class="mord mtight" style="">1</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span></span></span></span> and <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.83333em;vertical-align:-0.15em;"></span><span class="mord coloredeq eqq" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style="">2</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span></span></span></span> along the channel dimension (embedding dimension).</p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">91</span><span class="k">class</span> <span class="nc">SpacialGatingUnit</span><span class="p">(</span><span class="n">nn</span><span class="o">.</span><span class="n">Module</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-18'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-18'>#</a>
            </div>
            <ul><li><code class="highlight"><span></span><span class="n">d_z</span></code>
 is the dimensionality of <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span></span></span> </li>
<li><code class="highlight"><span></span><span class="n">seq_len</span></code>
 is the sequence length</li></ul>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">101</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">d_z</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">seq_len</span><span class="p">:</span> <span class="nb">int</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-19'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-19'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">106</span>        <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-20'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-20'>#</a>
            </div>
            <p>Normalization layer before applying <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1.036108em;vertical-align:-0.286108em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3361079999999999em;"><span style="top:-2.5500000000000003em;margin-left:-0.10764em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight coloredeq eqw" style=""><span class="mord mathnormal mtight" style="margin-right:0.13889em">W</span></span><span class="mpunct mtight">,</span><span class="mord mtight coloredeq eqz" style=""><span class="mord mathnormal mtight" style="">b</span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.286108em;"><span></span></span></span></span></span></span><span class="mopen">(</span><span class="mord">⋅</span><span class="mclose">)</span></span></span></span> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">108</span>        <span class="bp">self</span><span class="o">.</span><span class="n">norm</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">LayerNorm</span><span class="p">([</span><span class="n">d_z</span> <span class="o">//</span> <span class="mi">2</span><span class="p">])</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-21'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-21'>#</a>
            </div>
            <p>Weight <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqw" style=""><span class="mord mathnormal" style="margin-right:0.13889em">W</span></span></span></span></span> in <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1.036108em;vertical-align:-0.286108em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3361079999999999em;"><span style="top:-2.5500000000000003em;margin-left:-0.10764em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight coloredeq eqw" style=""><span class="mord mathnormal mtight" style="margin-right:0.13889em">W</span></span><span class="mpunct mtight">,</span><span class="mord mtight coloredeq eqz" style=""><span class="mord mathnormal mtight" style="">b</span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.286108em;"><span></span></span></span></span></span></span><span class="mopen">(</span><span class="mord">⋅</span><span class="mclose">)</span></span></span></span>.</p>
<p>The paper notes that it&#x27;s important to initialize weights to small values and the bias to <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.64444em;vertical-align:0em;"></span><span class="mord coloredeq eqs" style=""><span class="mord" style="">1</span></span></span></span></span>, so that during the initial training <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">s</span><span class="mopen">(</span><span class="mord">⋅</span><span class="mclose">)</span></span></span></span> is close to identity (apart from the split). </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">113</span>        <span class="bp">self</span><span class="o">.</span><span class="n">weight</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Parameter</span><span class="p">(</span><span class="n">torch</span><span class="o">.</span><span class="n">zeros</span><span class="p">(</span><span class="n">seq_len</span><span class="p">,</span> <span class="n">seq_len</span><span class="p">)</span><span class="o">.</span><span class="n">uniform_</span><span class="p">(</span><span class="o">-</span><span class="mf">0.01</span><span class="p">,</span> <span class="mf">0.01</span><span class="p">),</span> <span class="n">requires_grad</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-22'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-22'>#</a>
            </div>
            <p>Weight <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 coloredeq eqz" style=""><span class="mord mathnormal" style="">b</span></span></span></span></span> in <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1.036108em;vertical-align:-0.286108em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3361079999999999em;"><span style="top:-2.5500000000000003em;margin-left:-0.10764em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight coloredeq eqw" style=""><span class="mord mathnormal mtight" style="margin-right:0.13889em">W</span></span><span class="mpunct mtight">,</span><span class="mord mtight coloredeq eqz" style=""><span class="mord mathnormal mtight" style="">b</span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.286108em;"><span></span></span></span></span></span></span><span class="mopen">(</span><span class="mord">⋅</span><span class="mclose">)</span></span></span></span></p>
<p>The paper notes that it&#x27;s important to initialize bias to <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.64444em;vertical-align:0em;"></span><span class="mord coloredeq eqs" style=""><span class="mord" style="">1</span></span></span></span></span>. </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">117</span>        <span class="bp">self</span><span class="o">.</span><span class="n">bias</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Parameter</span><span class="p">(</span><span class="n">torch</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">seq_len</span><span class="p">),</span> <span class="n">requires_grad</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-23'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-23'>#</a>
            </div>
            <ul><li><code class="highlight"><span></span><span class="n">z</span></code>
 is the input <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span></span></span> of shape <code class="highlight"><span></span><span class="p">[</span><span class="n">seq_len</span><span class="p">,</span> <span class="n">batch_size</span><span class="p">,</span> <span class="n">d_z</span><span class="p">]</span></code>
 </li>
<li><code class="highlight"><span></span><span class="n">mask</span></code>
 is is a boolean mask of shape <code class="highlight"><span></span><span class="p">[</span><span class="n">seq_len</span><span class="p">,</span> <span class="n">seq_len</span><span class="p">,</span> <span class="mi">1</span><span class="p">]</span></code>
 that controls the visibility of tokens  among each other. The last dimension of size <code class="highlight"><span></span><span class="mi">1</span></code>
 is the batch, which we have in other transformer  implementations and was left for compatibility.</li></ul>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">119</span>    <span class="k">def</span> <span class="nf">forward</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">z</span><span class="p">:</span> <span class="n">torch</span><span class="o">.</span><span class="n">Tensor</span><span class="p">,</span> <span class="n">mask</span><span class="p">:</span> <span class="n">Optional</span><span class="p">[</span><span class="n">torch</span><span class="o">.</span><span class="n">Tensor</span><span class="p">]</span> <span class="o">=</span> <span class="kc">None</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-24'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-24'>#</a>
            </div>
            <p>Get sequence length </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">128</span>        <span class="n">seq_len</span> <span class="o">=</span> <span class="n">z</span><span class="o">.</span><span class="n">shape</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-25'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-25'>#</a>
            </div>
            <p>Split <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span></span></span></span> into <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.83333em;vertical-align:-0.15em;"></span><span class="mord coloredeq eqp" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight coloredeq eqs" style=""><span class="mord mtight" style="">1</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span></span></span></span> and <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.83333em;vertical-align:-0.15em;"></span><span class="mord coloredeq eqq" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style="">2</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span></span></span></span> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">130</span>        <span class="n">z1</span><span class="p">,</span> <span class="n">z2</span> <span class="o">=</span> <span class="n">torch</span><span class="o">.</span><span class="n">chunk</span><span class="p">(</span><span class="n">z</span><span class="p">,</span> <span class="mi">2</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>
        </div>
    </div>
    <div class='section' id='section-26'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-26'>#</a>
            </div>
            <p>Check mask </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">133</span>        <span class="k">if</span> <span class="n">mask</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-27'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-27'>#</a>
            </div>
            <p><code class="highlight"><span></span><span class="n">mask</span></code>
 has shape <code class="highlight"><span></span><span class="p">[</span><span class="n">seq_len_q</span><span class="p">,</span> <span class="n">seq_len_k</span><span class="p">,</span> <span class="n">batch_size</span><span class="p">]</span></code>
. The batch dimension should be of size <code class="highlight"><span></span><span class="mi">1</span></code>
 because this implementation supports only same mask for all samples in the batch. </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">137</span>            <span class="k">assert</span> <span class="n">mask</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="mi">1</span> <span class="ow">or</span> <span class="n">mask</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="n">seq_len</span>
<span class="lineno">138</span>            <span class="k">assert</span> <span class="n">mask</span><span class="o">.</span><span class="n">shape</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">==</span> <span class="n">seq_len</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-28'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-28'>#</a>
            </div>
            <p>Here we only support the same mask for all samples </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">140</span>            <span class="k">assert</span> <span class="n">mask</span><span class="o">.</span><span class="n">shape</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="o">==</span> <span class="mi">1</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-29'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-29'>#</a>
            </div>
            <p>Remove the batch dimension </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">142</span>            <span class="n">mask</span> <span class="o">=</span> <span class="n">mask</span><span class="p">[:,</span> <span class="p">:,</span> <span class="mi">0</span><span class="p">]</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-30'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-30'>#</a>
            </div>
            <p>Normalize <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.83333em;vertical-align:-0.15em;"></span><span class="mord coloredeq eqq" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style="">2</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span></span></span></span> before <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1.036108em;vertical-align:-0.286108em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3361079999999999em;"><span style="top:-2.5500000000000003em;margin-left:-0.10764em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight coloredeq eqw" style=""><span class="mord mathnormal mtight" style="margin-right:0.13889em">W</span></span><span class="mpunct mtight">,</span><span class="mord mtight coloredeq eqz" style=""><span class="mord mathnormal mtight" style="">b</span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.286108em;"><span></span></span></span></span></span></span><span class="mopen">(</span><span class="mord">⋅</span><span class="mclose">)</span></span></span></span> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">145</span>        <span class="n">z2</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">norm</span><span class="p">(</span><span class="n">z2</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-31'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-31'>#</a>
            </div>
            <p>Get the weight matrix; truncate if larger than <code class="highlight"><span></span><span class="n">seq_len</span></code>
 </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">147</span>        <span class="n">weight</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">weight</span><span class="p">[:</span><span class="n">seq_len</span><span class="p">,</span> <span class="p">:</span><span class="n">seq_len</span><span class="p">]</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-32'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-32'>#</a>
            </div>
            <p>Apply mask to the weights.</p>
<p>If <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.969438em;vertical-align:-0.286108em;"></span><span class="mord"><span class="mord coloredeq eqw" style=""><span class="mord mathnormal" style="margin-right:0.13889em">W</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.311664em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mathnormal mtight">i</span><span class="mpunct mtight">,</span><span class="mord mtight coloredeq eqbb" style=""><span class="mord mathnormal mtight" style="margin-right:0.05724em">j</span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.286108em;"><span></span></span></span></span></span></span></span></span></span> is <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.64444em;vertical-align:0em;"></span><span class="mord">0</span></span></span></span> then <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1.036108em;vertical-align:-0.286108em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3361079999999999em;"><span style="top:-2.5500000000000003em;margin-left:-0.10764em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight coloredeq eqw" style=""><span class="mord mathnormal mtight" style="margin-right:0.13889em">W</span></span><span class="mpunct mtight">,</span><span class="mord mtight coloredeq eqz" style=""><span class="mord mathnormal mtight" style="">b</span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.286108em;"><span></span></span></span></span></span></span><span class="mopen">(</span><span class="mord coloredeq eqq" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style="">2</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span><span class="mclose"><span class="mclose">)</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.31166399999999994em;"><span style="top:-2.5500000000000003em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">i</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span></span></span> will not get any information from token <span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.85396em;vertical-align:-0.19444em;"></span><span class="mord coloredeq eqbb" style=""><span class="mord mathnormal" style="margin-right:0.05724em">j</span></span></span></span></span>. </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">152</span>        <span class="k">if</span> <span class="n">mask</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
<span class="lineno">153</span>            <span class="n">weight</span> <span class="o">=</span> <span class="n">weight</span> <span class="o">*</span> <span class="n">mask</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-33'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-33'>#</a>
            </div>
            <p><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1.036108em;vertical-align:-0.286108em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3361079999999999em;"><span style="top:-2.5500000000000003em;margin-left:-0.10764em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight coloredeq eqw" style=""><span class="mord mathnormal mtight" style="margin-right:0.13889em">W</span></span><span class="mpunct mtight">,</span><span class="mord mtight coloredeq eqz" style=""><span class="mord mathnormal mtight" style="">b</span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.286108em;"><span></span></span></span></span></span></span><span class="mopen">(</span><span class="mord coloredeq eqq" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style="">2</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.83333em;vertical-align:-0.15em;"></span><span class="mord coloredeq eqw" style=""><span class="mord mathnormal" style="margin-right:0.13889em">W</span></span><span class="mord coloredeq eqq" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style="">2</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.69444em;vertical-align:0em;"></span><span class="mord coloredeq eqz" style=""><span class="mord mathnormal" style="">b</span></span></span></span></span> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">156</span>        <span class="n">z2</span> <span class="o">=</span> <span class="n">torch</span><span class="o">.</span><span class="n">einsum</span><span class="p">(</span><span class="s1">&#39;ij,jbd-&gt;ibd&#39;</span><span class="p">,</span> <span class="n">weight</span><span class="p">,</span> <span class="n">z2</span><span class="p">)</span> <span class="o">+</span> <span class="bp">self</span><span class="o">.</span><span class="n">bias</span><span class="p">[:</span><span class="n">seq_len</span><span class="p">,</span> <span class="kc">None</span><span class="p">,</span> <span class="kc">None</span><span class="p">]</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-34'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-34'>#</a>
            </div>
            <p><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1.036108em;vertical-align:-0.286108em;"></span><span class="mord coloredeq eqe" style=""><span class="mord coloredeq eqp" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight coloredeq eqs" style=""><span class="mord mtight" style="">1</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span><span class="mord coloredeq eqo" style=""><span class="mord" style="">⊙</span></span><span class="mord" style=""><span class="mord mathnormal" style="margin-right:0.10764em">f</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3361079999999999em;"><span style="top:-2.5500000000000003em;margin-left:-0.10764em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style=""><span class="mord mtight coloredeq eqw" style=""><span class="mord mathnormal mtight" style="margin-right:0.13889em">W</span></span><span class="mpunct mtight" style="">,</span><span class="mord mtight coloredeq eqz" style=""><span class="mord mathnormal mtight" style="">b</span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.286108em;"><span></span></span></span></span></span></span><span class="mopen" style="">(</span><span class="mord coloredeq eqq" style=""><span class="mord" style=""><span class="mord coloredeq eqy" style=""><span class="mord mathnormal" style="margin-right:0.07153em">Z</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style="">2</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span></span><span class="mclose" style="">)</span></span></span></span></span> </p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">159</span>        <span class="k">return</span> <span class="n">z1</span> <span class="o">*</span> <span class="n">z2</span></pre></div>
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