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            <h1>U-Net model for <a href="index.html">Denoising Diffusion Probabilistic Models (DDPM)</a></h1>
<p>This is a <a href="../../unet/index.html">U-Net</a> based model to predict noise <span ><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" style="color:lightgreen"><span class="mord mathnormal" style="">ϵ</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.33610799999999996em;"><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" style=""><span class="mord mathnormal mtight" style="margin-right:0.02778em">θ</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 class="mopen">(</span><span class="mord"><span class="mord mathnormal">x</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.2805559999999999em;"><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 mtight coloredeq eqj" style=""><span class="mord mathnormal mtight" style="">t</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 class="mpunct">,</span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord coloredeq eqj" style=""><span class="mord mathnormal" style="">t</span></span><span class="mclose">)</span></span></span></span></span>.</p>
<p>U-Net is a gets it&#x27;s name from the U shape in the model diagram. It processes a given image by progressively lowering (halving) the feature map resolution and then increasing the resolution. There are pass-through connection at each resolution.</p>
<p><img alt="U-Net diagram from paper" src="../../unet/unet.png"></p>
<p>This implementation contains a bunch of modifications to original U-Net (residual blocks, multi-head attention)  and also adds time-step embeddings <span ><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.61508em;vertical-align:0em;"></span><span class="mord coloredeq eqj" style=""><span class="mord mathnormal" style="">t</span></span></span></span></span></span>.</p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">24</span><span></span><span class="kn">import</span> <span class="nn">math</span>
<span class="lineno">25</span><span class="kn">from</span> <span class="nn">typing</span> <span class="kn">import</span> <span class="n">Optional</span><span class="p">,</span> <span class="n">Tuple</span><span class="p">,</span> <span class="n">Union</span><span class="p">,</span> <span class="n">List</span>
<span class="lineno">26</span>
<span class="lineno">27</span><span class="kn">import</span> <span class="nn">torch</span>
<span class="lineno">28</span><span class="kn">from</span> <span class="nn">torch</span> <span class="kn">import</span> <span class="n">nn</span>
<span class="lineno">29</span>
<span class="lineno">30</span><span class="kn">from</span> <span class="nn">labml_helpers.module</span> <span class="kn">import</span> <span class="n">Module</span></pre></div>
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    <div class='section' id='section-1'>
        <div class='docs doc-strings'>
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                <a href='#section-1'>#</a>
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            <h3>Swish actiavation function</h3>
<p><span ><span class="katex-display"><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.44445em;vertical-align:0em;"></span><span class="mord mathnormal">x</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:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">σ</span><span class="mopen">(</span><span class="mord mathnormal">x</span><span class="mclose">)</span></span></span></span></span></span></p>

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            <div class="highlight"><pre><span class="lineno">33</span><span class="k">class</span> <span class="nc">Swish</span><span class="p">(</span><span class="n">Module</span><span class="p">):</span></pre></div>
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            <div class="highlight"><pre><span class="lineno">40</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">x</span><span class="p">):</span>
<span class="lineno">41</span>        <span class="k">return</span> <span class="n">x</span> <span class="o">*</span> <span class="n">torch</span><span class="o">.</span><span class="n">sigmoid</span><span class="p">(</span><span class="n">x</span><span class="p">)</span></pre></div>
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                <a href='#section-3'>#</a>
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            <h3>Embeddings for <span ><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.61508em;vertical-align:0em;"></span><span class="mord coloredeq eqj" style=""><span class="mord mathnormal" style="">t</span></span></span></span></span></span></h3>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">44</span><span class="k">class</span> <span class="nc">TimeEmbedding</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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                <a href='#section-4'>#</a>
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            <ul><li><code  class="highlight"><span></span><span class="n">n_channels</span></code>
 is the number of dimensions in the embedding</li></ul>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">49</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">n_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">):</span></pre></div>
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    <div class='section' id='section-5'>
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            <div class='section-link'>
                <a href='#section-5'>#</a>
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        </div>
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            <div class="highlight"><pre><span class="lineno">53</span>        <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span>
<span class="lineno">54</span>        <span class="bp">self</span><span class="o">.</span><span class="n">n_channels</span> <span class="o">=</span> <span class="n">n_channels</span></pre></div>
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            <p>First linear layer </p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">56</span>        <span class="bp">self</span><span class="o">.</span><span class="n">lin1</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="bp">self</span><span class="o">.</span><span class="n">n_channels</span> <span class="o">//</span> <span class="mi">4</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">n_channels</span><span class="p">)</span></pre></div>
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                <a href='#section-7'>#</a>
            </div>
            <p>Activation </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">58</span>        <span class="bp">self</span><span class="o">.</span><span class="n">act</span> <span class="o">=</span> <span class="n">Swish</span><span class="p">()</span></pre></div>
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            <p>Second linear layer </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">60</span>        <span class="bp">self</span><span class="o">.</span><span class="n">lin2</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="bp">self</span><span class="o">.</span><span class="n">n_channels</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">n_channels</span><span class="p">)</span></pre></div>
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    <div class='section' id='section-9'>
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                <a href='#section-9'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">62</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">t</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>
        </div>
    </div>
    <div class='section' id='section-10'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-10'>#</a>
            </div>
            <p>Create sinusoidal position embeddings <a href="../../transformers/positional_encoding.html">same as those from the transformer</a></p>
<span ><span class="katex-display"><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:6.600059999999999em;vertical-align:-3.0500299999999996em;"></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:3.5500299999999996em;"><span style="top:-5.55003em;"><span class="pstrut" style="height:3.75em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.13889em;">P</span><span class="mord"><span class="mord mathnormal" style="margin-right:0.05764em;">E</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.0448em;"><span style="top:-2.4231360000000004em;margin-left:-0.05764em;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 eqj" style=""><span class="mord mathnormal mtight" style="">t</span></span><span class="mpunct mtight">,</span><span class="mord mathnormal mtight">i</span></span></span></span><span style="top:-3.2198em;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="mopen mtight">(</span><span class="mord mtight">1</span><span class="mclose mtight">)</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.412972em;"><span></span></span></span></span></span></span></span></span><span style="top:-2.2500000000000004em;"><span class="pstrut" style="height:3.75em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.13889em;">P</span><span class="mord"><span class="mord mathnormal" style="margin-right:0.05764em;">E</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.0448em;"><span style="top:-2.4231360000000004em;margin-left:-0.05764em;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 eqj" style=""><span class="mord mathnormal mtight" style="">t</span></span><span class="mpunct mtight">,</span><span class="mord mathnormal mtight">i</span></span></span></span><span style="top:-3.2198em;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="mopen mtight">(</span><span class="mord mtight">2</span><span class="mclose mtight">)</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.412972em;"><span></span></span></span></span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:3.0500299999999996em;"><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:3.5500299999999996em;"><span style="top:-5.55003em;"><span class="pstrut" style="height:3.75em;"></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="mord mathnormal">in</span><span class="mord"><span class="delimsizing size4">(</span></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.29208em;"><span style="top:-2.121225em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">1000</span><span class="mord"><span class="mord">0</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.9887749999999998em;"><span style="top:-3.3902150000000004em;margin-right:0.05em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight"><span class="mopen nulldelimiter sizing reset-size3 size6"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8550857142857142em;"><span style="top:-2.656em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size3 size1 mtight"><span class="mord mtight"><span class="mord mtight coloredeq eqi" style=""><span class="mord mathnormal mtight" style="">d</span></span><span class="mbin mtight">−</span><span class="mord mtight">1</span></span></span></span><span style="top:-3.2255em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line mtight" style="border-bottom-width:0.049em;"></span></span><span style="top:-3.384em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size3 size1 mtight"><span class="mord mtight"><span class="mord mathnormal mtight">i</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.40352142857142853em;"><span></span></span></span></span></span><span class="mclose nulldelimiter sizing reset-size3 size6"></span></span></span></span></span></span></span></span></span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord coloredeq eqj" style=""><span class="mord mathnormal" style="">t</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.8787749999999999em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mord"><span class="delimsizing size4">)</span></span></span></span><span style="top:-2.2500000000000004em;"><span class="pstrut" style="height:3.75em;"></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">cos</span><span class="mord"><span class="delimsizing size4">(</span></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.29208em;"><span style="top:-2.121225em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">1000</span><span class="mord"><span class="mord">0</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.9887749999999998em;"><span style="top:-3.3902150000000004em;margin-right:0.05em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight"><span class="mopen nulldelimiter sizing reset-size3 size6"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8550857142857142em;"><span style="top:-2.656em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size3 size1 mtight"><span class="mord mtight"><span class="mord mtight coloredeq eqi" style=""><span class="mord mathnormal mtight" style="">d</span></span><span class="mbin mtight">−</span><span class="mord mtight">1</span></span></span></span><span style="top:-3.2255em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line mtight" style="border-bottom-width:0.049em;"></span></span><span style="top:-3.384em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size3 size1 mtight"><span class="mord mtight"><span class="mord mathnormal mtight">i</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.40352142857142853em;"><span></span></span></span></span></span><span class="mclose nulldelimiter sizing reset-size3 size6"></span></span></span></span></span></span></span></span></span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord coloredeq eqj" style=""><span class="mord mathnormal" style="">t</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.8787749999999999em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mord"><span class="delimsizing size4">)</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:3.0500299999999996em;"><span></span></span></span></span></span></span></span></span></span></span></span></span><p>where <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 coloredeq eqi" style=""><span class="mord mathnormal" style="">d</span></span></span></span></span></span> is <code  class="highlight"><span></span><span class="n">half_dim</span></code>
 </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">72</span>        <span class="n">half_dim</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">n_channels</span> <span class="o">//</span> <span class="mi">8</span>
<span class="lineno">73</span>        <span class="n">emb</span> <span class="o">=</span> <span class="n">math</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="mi">10_000</span><span class="p">)</span> <span class="o">/</span> <span class="p">(</span><span class="n">half_dim</span> <span class="o">-</span> <span class="mi">1</span><span class="p">)</span>
<span class="lineno">74</span>        <span class="n">emb</span> <span class="o">=</span> <span class="n">torch</span><span class="o">.</span><span class="n">exp</span><span class="p">(</span><span class="n">torch</span><span class="o">.</span><span class="n">arange</span><span class="p">(</span><span class="n">half_dim</span><span class="p">,</span> <span class="n">device</span><span class="o">=</span><span class="n">t</span><span class="o">.</span><span class="n">device</span><span class="p">)</span> <span class="o">*</span> <span class="o">-</span><span class="n">emb</span><span class="p">)</span>
<span class="lineno">75</span>        <span class="n">emb</span> <span class="o">=</span> <span class="n">t</span><span class="p">[:,</span> <span class="kc">None</span><span class="p">]</span> <span class="o">*</span> <span class="n">emb</span><span class="p">[</span><span class="kc">None</span><span class="p">,</span> <span class="p">:]</span>
<span class="lineno">76</span>        <span class="n">emb</span> <span class="o">=</span> <span class="n">torch</span><span class="o">.</span><span class="n">cat</span><span class="p">((</span><span class="n">emb</span><span class="o">.</span><span class="n">sin</span><span class="p">(),</span> <span class="n">emb</span><span class="o">.</span><span class="n">cos</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-11'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-11'>#</a>
            </div>
            <p>Transform with the MLP </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">79</span>        <span class="n">emb</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">act</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">lin1</span><span class="p">(</span><span class="n">emb</span><span class="p">))</span>
<span class="lineno">80</span>        <span class="n">emb</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">lin2</span><span class="p">(</span><span class="n">emb</span><span class="p">)</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> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">83</span>        <span class="k">return</span> <span class="n">emb</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-13'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-13'>#</a>
            </div>
            <h3>Residual block</h3>
<p>A residual block has two convolution layers with group normalization. Each resolution is processed with two residual blocks.</p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">86</span><span class="k">class</span> <span class="nc">ResidualBlock</span><span class="p">(</span><span class="n">Module</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-14'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-14'>#</a>
            </div>
            <ul><li><code  class="highlight"><span></span><span class="n">in_channels</span></code>
 is the number of input channels </li>
<li><code  class="highlight"><span></span><span class="n">out_channels</span></code>
 is the number of input channels </li>
<li><code  class="highlight"><span></span><span class="n">time_channels</span></code>
 is the number channels in the time step (<span ><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.61508em;vertical-align:0em;"></span><span class="mord coloredeq eqj" style=""><span class="mord mathnormal" style="">t</span></span></span></span></span></span>) embeddings </li>
<li><code  class="highlight"><span></span><span class="n">n_groups</span></code>
 is the number of groups for <a href="../../normalization/group_norm/index.html">group normalization</a> </li>
<li><code  class="highlight"><span></span><span class="n">dropout</span></code>
 is the dropout rate</li></ul>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">94</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">in_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">time_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span>
<span class="lineno">95</span>                 <span class="n">n_groups</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="mi">32</span><span class="p">,</span> <span class="n">dropout</span><span class="p">:</span> <span class="nb">float</span> <span class="o">=</span> <span class="mf">0.1</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>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">103</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-16'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-16'>#</a>
            </div>
            <p>Group normalization and the first convolution layer </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">105</span>        <span class="bp">self</span><span class="o">.</span><span class="n">norm1</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">GroupNorm</span><span class="p">(</span><span class="n">n_groups</span><span class="p">,</span> <span class="n">in_channels</span><span class="p">)</span>
<span class="lineno">106</span>        <span class="bp">self</span><span class="o">.</span><span class="n">act1</span> <span class="o">=</span> <span class="n">Swish</span><span class="p">()</span>
<span class="lineno">107</span>        <span class="bp">self</span><span class="o">.</span><span class="n">conv1</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Conv2d</span><span class="p">(</span><span class="n">in_channels</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">,</span> <span class="n">kernel_size</span><span class="o">=</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">),</span> <span class="n">padding</span><span class="o">=</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">))</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-17'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-17'>#</a>
            </div>
            <p>Group normalization and the second convolution layer </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">110</span>        <span class="bp">self</span><span class="o">.</span><span class="n">norm2</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">GroupNorm</span><span class="p">(</span><span class="n">n_groups</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">)</span>
<span class="lineno">111</span>        <span class="bp">self</span><span class="o">.</span><span class="n">act2</span> <span class="o">=</span> <span class="n">Swish</span><span class="p">()</span>
<span class="lineno">112</span>        <span class="bp">self</span><span class="o">.</span><span class="n">conv2</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Conv2d</span><span class="p">(</span><span class="n">out_channels</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">,</span> <span class="n">kernel_size</span><span class="o">=</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">),</span> <span class="n">padding</span><span class="o">=</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">))</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-18'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-18'>#</a>
            </div>
            <p>If the number of input channels is not equal to the number of output channels we have to project the shortcut connection </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">116</span>        <span class="k">if</span> <span class="n">in_channels</span> <span class="o">!=</span> <span class="n">out_channels</span><span class="p">:</span>
<span class="lineno">117</span>            <span class="bp">self</span><span class="o">.</span><span class="n">shortcut</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Conv2d</span><span class="p">(</span><span class="n">in_channels</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">,</span> <span class="n">kernel_size</span><span class="o">=</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">))</span>
<span class="lineno">118</span>        <span class="k">else</span><span class="p">:</span>
<span class="lineno">119</span>            <span class="bp">self</span><span class="o">.</span><span class="n">shortcut</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Identity</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>
            <p>Linear layer for time embeddings </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">122</span>        <span class="bp">self</span><span class="o">.</span><span class="n">time_emb</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">time_channels</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">)</span>
<span class="lineno">123</span>        <span class="bp">self</span><span class="o">.</span><span class="n">time_act</span> <span class="o">=</span> <span class="n">Swish</span><span class="p">()</span>
<span class="lineno">124</span>
<span class="lineno">125</span>        <span class="bp">self</span><span class="o">.</span><span class="n">dropout</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Dropout</span><span class="p">(</span><span class="n">dropout</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-20'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-20'>#</a>
            </div>
            <ul><li><code  class="highlight"><span></span><span class="n">x</span></code>
 has shape <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">in_channels</span><span class="p">,</span> <span class="n">height</span><span class="p">,</span> <span class="n">width</span><span class="p">]</span></code>
 </li>
<li><code  class="highlight"><span></span><span class="n">t</span></code>
 has shape <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">time_channels</span><span class="p">]</span></code>
</li></ul>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">127</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">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">t</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>
        </div>
    </div>
    <div class='section' id='section-21'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-21'>#</a>
            </div>
            <p>First convolution layer </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">133</span>        <span class="n">h</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">conv1</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">act1</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">norm1</span><span class="p">(</span><span class="n">x</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>Add time embeddings </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">135</span>        <span class="n">h</span> <span class="o">+=</span> <span class="bp">self</span><span class="o">.</span><span class="n">time_emb</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">time_act</span><span class="p">(</span><span class="n">t</span><span class="p">))[:,</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-23'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-23'>#</a>
            </div>
            <p>Second convolution layer </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">137</span>        <span class="n">h</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">conv2</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">dropout</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">act2</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">norm2</span><span class="p">(</span><span class="n">h</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>Add the shortcut connection and return </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">140</span>        <span class="k">return</span> <span class="n">h</span> <span class="o">+</span> <span class="bp">self</span><span class="o">.</span><span class="n">shortcut</span><span class="p">(</span><span class="n">x</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-25'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-25'>#</a>
            </div>
            <h3>Attention block</h3>
<p>This is similar to <a href="../../transformers/mha.html">transformer multi-head attention</a>.</p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">143</span><span class="k">class</span> <span class="nc">AttentionBlock</span><span class="p">(</span><span class="n">Module</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-26'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-26'>#</a>
            </div>
            <ul><li><code  class="highlight"><span></span><span class="n">n_channels</span></code>
 is the number of channels in the input </li>
<li><code  class="highlight"><span></span><span class="n">n_heads</span></code>
 is the number of heads in multi-head attention </li>
<li><code  class="highlight"><span></span><span class="n">d_k</span></code>
 is the number of dimensions in each head </li>
<li><code  class="highlight"><span></span><span class="n">n_groups</span></code>
 is the number of groups for <a href="../../normalization/group_norm/index.html">group normalization</a></li></ul>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">150</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">n_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">n_heads</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="mi">1</span><span class="p">,</span> <span class="n">d_k</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="kc">None</span><span class="p">,</span> <span class="n">n_groups</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="mi">32</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>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">157</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-28'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-28'>#</a>
            </div>
            <p>Default <code  class="highlight"><span></span><span class="n">d_k</span></code>
 </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">160</span>        <span class="k">if</span> <span class="n">d_k</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="lineno">161</span>            <span class="n">d_k</span> <span class="o">=</span> <span class="n">n_channels</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>Normalization layer </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">163</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">GroupNorm</span><span class="p">(</span><span class="n">n_groups</span><span class="p">,</span> <span class="n">n_channels</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>Projections for query, key and values </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">165</span>        <span class="bp">self</span><span class="o">.</span><span class="n">projection</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">n_channels</span><span class="p">,</span> <span class="n">n_heads</span> <span class="o">*</span> <span class="n">d_k</span> <span class="o">*</span> <span class="mi">3</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>Linear layer for final transformation </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">167</span>        <span class="bp">self</span><span class="o">.</span><span class="n">output</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">n_heads</span> <span class="o">*</span> <span class="n">d_k</span><span class="p">,</span> <span class="n">n_channels</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>Scale for dot-product attention </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">169</span>        <span class="bp">self</span><span class="o">.</span><span class="n">scale</span> <span class="o">=</span> <span class="n">d_k</span> <span class="o">**</span> <span class="o">-</span><span class="mf">0.5</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> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">171</span>        <span class="bp">self</span><span class="o">.</span><span class="n">n_heads</span> <span class="o">=</span> <span class="n">n_heads</span>
<span class="lineno">172</span>        <span class="bp">self</span><span class="o">.</span><span class="n">d_k</span> <span class="o">=</span> <span class="n">d_k</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-34'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-34'>#</a>
            </div>
            <ul><li><code  class="highlight"><span></span><span class="n">x</span></code>
 has shape <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">in_channels</span><span class="p">,</span> <span class="n">height</span><span class="p">,</span> <span class="n">width</span><span class="p">]</span></code>
 </li>
<li><code  class="highlight"><span></span><span class="n">t</span></code>
 has shape <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">time_channels</span><span class="p">]</span></code>
</li></ul>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">174</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">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">t</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-35'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-35'>#</a>
            </div>
            <p><code  class="highlight"><span></span><span class="n">t</span></code>
 is not used, but it&#x27;s kept in the arguments because for the attention layer function signature to match with <code  class="highlight"><span></span><span class="n">ResidualBlock</span></code>
. </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">181</span>        <span class="n">_</span> <span class="o">=</span> <span class="n">t</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-36'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-36'>#</a>
            </div>
            <p>Get shape </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">183</span>        <span class="n">batch_size</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">,</span> <span class="n">height</span><span class="p">,</span> <span class="n">width</span> <span class="o">=</span> <span class="n">x</span><span class="o">.</span><span class="n">shape</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-37'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-37'>#</a>
            </div>
            <p>Change <code  class="highlight"><span></span><span class="n">x</span></code>
 to shape <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">seq</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">]</span></code>
 </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">185</span>        <span class="n">x</span> <span class="o">=</span> <span class="n">x</span><span class="o">.</span><span class="n">view</span><span class="p">(</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">)</span><span class="o">.</span><span class="n">permute</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-38'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-38'>#</a>
            </div>
            <p>Get query, key, and values (concatenated) and shape it to <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">seq</span><span class="p">,</span> <span class="n">n_heads</span><span class="p">,</span> <span class="mi">3</span> <span class="o">*</span> <span class="n">d_k</span><span class="p">]</span></code>
 </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">187</span>        <span class="n">qkv</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">projection</span><span class="p">(</span><span class="n">x</span><span class="p">)</span><span class="o">.</span><span class="n">view</span><span class="p">(</span><span class="n">batch_size</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">n_heads</span><span class="p">,</span> <span class="mi">3</span> <span class="o">*</span> <span class="bp">self</span><span class="o">.</span><span class="n">d_k</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-39'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-39'>#</a>
            </div>
            <p>Split query, key, and values. Each of them will have shape <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">seq</span><span class="p">,</span> <span class="n">n_heads</span><span class="p">,</span> <span class="n">d_k</span><span class="p">]</span></code>
 </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">189</span>        <span class="n">q</span><span class="p">,</span> <span class="n">k</span><span class="p">,</span> <span class="n">v</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">qkv</span><span class="p">,</span> <span class="mi">3</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-40'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-40'>#</a>
            </div>
            <p>Calculate scaled dot-product <span ><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1.633028em;vertical-align:-0.538em;"></span><span class="mord coloredeq eqd" style=""><span class="mord" style=""><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.095028em;"><span style="top:-2.5864385em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style=""><span class="mord sqrt mtight" style=""><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8622307142857143em;"><span class="svg-align" style="top:-3em;"><span class="pstrut" style="height:3em;"></span><span class="mord mtight" style="padding-left:0.833em"><span class="mord mtight" style=""><span class="mord mtight" style=""><span class="mord mathnormal mtight coloredeq eqi" style="">d</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3448em;"><span style="top:-2.3487714285714287em;margin-right:0.07142857142857144em;"><span class="pstrut" style="height:2.5em;"></span><span class="sizing reset-size3 size1 mtight" style=""><span class="mord mathnormal mtight" style="margin-right:0.03148em">k</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15122857142857138em;"><span></span></span></span></span></span></span></span></span><span style="top:-2.8222307142857144em;"><span class="pstrut" style="height:3em;"></span><span class="hide-tail mtight" style="min-width:0.853em;height:1.08em"><svg height="1.08em" preserveaspectratio="xMinYMin slice" viewbox="0 0 400000 1080" width="400em" xmlns="http://www.w3.org/2000/svg"><path d="M95,702
c-2.7,0,-7.17,-2.7,-13.5,-8c-5.8,-5.3,-9.5,-10,-9.5,-14
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H400000v40H845.2724
s-225.272,467,-225.272,467s-235,486,-235,486c-2.7,4.7,-9,7,-19,7
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M834 80h400000v40h-400000z"></path></svg></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.17776928571428574em;"><span></span></span></span></span></span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em"></span></span><span style="top:-3.446108em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style=""><span class="mord mathnormal mtight" style="">Q</span><span class="mord mtight" style=""><span class="mord mathnormal mtight" style="margin-right:0.07153em">K</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.9270285714285713em;"><span style="top:-2.931em;margin-right:0.07142857142857144em;"><span class="pstrut" style="height:2.5em;"></span><span class="sizing reset-size3 size1 mtight" style=""><span class="mord mtight" style="">⊤</span></span></span></span></span></span></span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.538em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span></span></span></span></span></span> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">191</span>        <span class="n">attn</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;bihd,bjhd-&gt;bijh&#39;</span><span class="p">,</span> <span class="n">q</span><span class="p">,</span> <span class="n">k</span><span class="p">)</span> <span class="o">*</span> <span class="bp">self</span><span class="o">.</span><span class="n">scale</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-41'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-41'>#</a>
            </div>
            <p>Softmax along the sequence dimension <span ><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:3.0000299999999998em;vertical-align:-1.25003em;"></span><span class="mord"><span class="mop op-limits"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.6944399999999998em;"><span style="top:-2.20556em;margin-left:0em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mathnormal mtight">se</span><span class="mord mathnormal mtight" style="margin-right:0.03588em;">q</span></span></span></span><span style="top:-3em;"><span class="pstrut" style="height:3em;"></span><span><span class="mop"><span class="mord mathnormal">so</span><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="mord coloredeq eqj" style=""><span class="mord mathnormal" style="">t</span></span><span class="mord mathnormal">ma</span><span class="mord mathnormal">x</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:1.030548em;"><span></span></span></span></span></span></span><span class="mord"><span class="delimsizing size4">(</span></span><span class="mord coloredeq eqd" style=""><span class="mord" style=""><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.095028em;"><span style="top:-2.5864385em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style=""><span class="mord sqrt mtight" style=""><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8622307142857143em;"><span class="svg-align" style="top:-3em;"><span class="pstrut" style="height:3em;"></span><span class="mord mtight" style="padding-left:0.833em"><span class="mord mtight" style=""><span class="mord mtight" style=""><span class="mord mathnormal mtight coloredeq eqi" style="">d</span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3448em;"><span style="top:-2.3487714285714287em;margin-right:0.07142857142857144em;"><span class="pstrut" style="height:2.5em;"></span><span class="sizing reset-size3 size1 mtight" style=""><span class="mord mathnormal mtight" style="margin-right:0.03148em">k</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15122857142857138em;"><span></span></span></span></span></span></span></span></span><span style="top:-2.8222307142857144em;"><span class="pstrut" style="height:3em;"></span><span class="hide-tail mtight" style="min-width:0.853em;height:1.08em"><svg height="1.08em" preserveaspectratio="xMinYMin slice" viewbox="0 0 400000 1080" width="400em" xmlns="http://www.w3.org/2000/svg"><path d="M95,702
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M834 80h400000v40h-400000z"></path></svg></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.17776928571428574em;"><span></span></span></span></span></span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em"></span></span><span style="top:-3.446108em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight" style=""><span class="mord mtight" style=""><span class="mord mathnormal mtight" style="">Q</span><span class="mord mtight" style=""><span class="mord mathnormal mtight" style="margin-right:0.07153em">K</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.9270285714285713em;"><span style="top:-2.931em;margin-right:0.07142857142857144em;"><span class="pstrut" style="height:2.5em;"></span><span class="sizing reset-size3 size1 mtight" style=""><span class="mord mtight" style="">⊤</span></span></span></span></span></span></span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.538em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span></span><span class="mord"><span class="delimsizing size4">)</span></span></span></span></span></span> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">193</span>        <span class="n">attn</span> <span class="o">=</span> <span class="n">attn</span><span class="o">.</span><span class="n">softmax</span><span class="p">(</span><span class="n">dim</span><span class="o">=</span><span class="mi">2</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-42'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-42'>#</a>
            </div>
            <p>Multiply by values </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">195</span>        <span class="n">res</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;bijh,bjhd-&gt;bihd&#39;</span><span class="p">,</span> <span class="n">attn</span><span class="p">,</span> <span class="n">v</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-43'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-43'>#</a>
            </div>
            <p>Reshape to <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">seq</span><span class="p">,</span> <span class="n">n_heads</span> <span class="o">*</span> <span class="n">d_k</span><span class="p">]</span></code>
 </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">197</span>        <span class="n">res</span> <span class="o">=</span> <span class="n">res</span><span class="o">.</span><span class="n">view</span><span class="p">(</span><span class="n">batch_size</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">n_heads</span> <span class="o">*</span> <span class="bp">self</span><span class="o">.</span><span class="n">d_k</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-44'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-44'>#</a>
            </div>
            <p>Transform to <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">seq</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">]</span></code>
 </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">199</span>        <span class="n">res</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">output</span><span class="p">(</span><span class="n">res</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-45'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-45'>#</a>
            </div>
            <p>Add skip connection </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">202</span>        <span class="n">res</span> <span class="o">+=</span> <span class="n">x</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-46'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-46'>#</a>
            </div>
            <p>Change to shape <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">in_channels</span><span class="p">,</span> <span class="n">height</span><span class="p">,</span> <span class="n">width</span><span class="p">]</span></code>
 </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">205</span>        <span class="n">res</span> <span class="o">=</span> <span class="n">res</span><span class="o">.</span><span class="n">permute</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span><span class="o">.</span><span class="n">view</span><span class="p">(</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">,</span> <span class="n">height</span><span class="p">,</span> <span class="n">width</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-47'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-47'>#</a>
            </div>
            <p> </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">208</span>        <span class="k">return</span> <span class="n">res</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-48'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-48'>#</a>
            </div>
            <h3>Down block</h3>
<p>This combines <code  class="highlight"><span></span><span class="n">ResidualBlock</span></code>
 and <code  class="highlight"><span></span><span class="n">AttentionBlock</span></code>
. These are used in the first half of U-Net at each resolution.</p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">211</span><span class="k">class</span> <span class="nc">DownBlock</span><span class="p">(</span><span class="n">Module</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-49'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-49'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">218</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">in_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">time_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">has_attn</span><span class="p">:</span> <span class="nb">bool</span><span class="p">):</span>
<span class="lineno">219</span>        <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span>
<span class="lineno">220</span>        <span class="bp">self</span><span class="o">.</span><span class="n">res</span> <span class="o">=</span> <span class="n">ResidualBlock</span><span class="p">(</span><span class="n">in_channels</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">,</span> <span class="n">time_channels</span><span class="p">)</span>
<span class="lineno">221</span>        <span class="k">if</span> <span class="n">has_attn</span><span class="p">:</span>
<span class="lineno">222</span>            <span class="bp">self</span><span class="o">.</span><span class="n">attn</span> <span class="o">=</span> <span class="n">AttentionBlock</span><span class="p">(</span><span class="n">out_channels</span><span class="p">)</span>
<span class="lineno">223</span>        <span class="k">else</span><span class="p">:</span>
<span class="lineno">224</span>            <span class="bp">self</span><span class="o">.</span><span class="n">attn</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Identity</span><span class="p">()</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-50'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-50'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">226</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">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">t</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="lineno">227</span>        <span class="n">x</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">res</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">t</span><span class="p">)</span>
<span class="lineno">228</span>        <span class="n">x</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">attn</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>
<span class="lineno">229</span>        <span class="k">return</span> <span class="n">x</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-51'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-51'>#</a>
            </div>
            <h3>Up block</h3>
<p>This combines <code  class="highlight"><span></span><span class="n">ResidualBlock</span></code>
 and <code  class="highlight"><span></span><span class="n">AttentionBlock</span></code>
. These are used in the second half of U-Net at each resolution.</p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">232</span><span class="k">class</span> <span class="nc">UpBlock</span><span class="p">(</span><span class="n">Module</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-52'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-52'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">239</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">in_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">time_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">has_attn</span><span class="p">:</span> <span class="nb">bool</span><span class="p">):</span>
<span class="lineno">240</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-53'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-53'>#</a>
            </div>
            <p>The input has <code  class="highlight"><span></span><span class="n">in_channels</span> <span class="o">+</span> <span class="n">out_channels</span></code>
 because we concatenate the output of the same resolution from the first half of the U-Net </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">243</span>        <span class="bp">self</span><span class="o">.</span><span class="n">res</span> <span class="o">=</span> <span class="n">ResidualBlock</span><span class="p">(</span><span class="n">in_channels</span> <span class="o">+</span> <span class="n">out_channels</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">,</span> <span class="n">time_channels</span><span class="p">)</span>
<span class="lineno">244</span>        <span class="k">if</span> <span class="n">has_attn</span><span class="p">:</span>
<span class="lineno">245</span>            <span class="bp">self</span><span class="o">.</span><span class="n">attn</span> <span class="o">=</span> <span class="n">AttentionBlock</span><span class="p">(</span><span class="n">out_channels</span><span class="p">)</span>
<span class="lineno">246</span>        <span class="k">else</span><span class="p">:</span>
<span class="lineno">247</span>            <span class="bp">self</span><span class="o">.</span><span class="n">attn</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Identity</span><span class="p">()</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-54'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-54'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">249</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">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">t</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="lineno">250</span>        <span class="n">x</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">res</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">t</span><span class="p">)</span>
<span class="lineno">251</span>        <span class="n">x</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">attn</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>
<span class="lineno">252</span>        <span class="k">return</span> <span class="n">x</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-55'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-55'>#</a>
            </div>
            <h3>Middle block</h3>
<p>It combines a <code  class="highlight"><span></span><span class="n">ResidualBlock</span></code>
, <code  class="highlight"><span></span><span class="n">AttentionBlock</span></code>
, followed by another <code  class="highlight"><span></span><span class="n">ResidualBlock</span></code>
. This block is applied at the lowest resolution of the U-Net.</p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">255</span><span class="k">class</span> <span class="nc">MiddleBlock</span><span class="p">(</span><span class="n">Module</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-56'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-56'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">263</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">n_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">time_channels</span><span class="p">:</span> <span class="nb">int</span><span class="p">):</span>
<span class="lineno">264</span>        <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span>
<span class="lineno">265</span>        <span class="bp">self</span><span class="o">.</span><span class="n">res1</span> <span class="o">=</span> <span class="n">ResidualBlock</span><span class="p">(</span><span class="n">n_channels</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">,</span> <span class="n">time_channels</span><span class="p">)</span>
<span class="lineno">266</span>        <span class="bp">self</span><span class="o">.</span><span class="n">attn</span> <span class="o">=</span> <span class="n">AttentionBlock</span><span class="p">(</span><span class="n">n_channels</span><span class="p">)</span>
<span class="lineno">267</span>        <span class="bp">self</span><span class="o">.</span><span class="n">res2</span> <span class="o">=</span> <span class="n">ResidualBlock</span><span class="p">(</span><span class="n">n_channels</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">,</span> <span class="n">time_channels</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-57'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-57'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">269</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">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">t</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="lineno">270</span>        <span class="n">x</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">res1</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">t</span><span class="p">)</span>
<span class="lineno">271</span>        <span class="n">x</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">attn</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>
<span class="lineno">272</span>        <span class="n">x</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">res2</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">t</span><span class="p">)</span>
<span class="lineno">273</span>        <span class="k">return</span> <span class="n">x</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-58'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-58'>#</a>
            </div>
            <h3>Scale up the feature map by <span ><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:0.72777em;vertical-align:-0.08333em;"></span><span class="mord">2</span><span class="mord">×</span></span></span></span></span></h3>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">276</span><span class="k">class</span> <span class="nc">Upsample</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-59'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-59'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">281</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">n_channels</span><span class="p">):</span>
<span class="lineno">282</span>        <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span>
<span class="lineno">283</span>        <span class="bp">self</span><span class="o">.</span><span class="n">conv</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">ConvTranspose2d</span><span class="p">(</span><span class="n">n_channels</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">,</span> <span class="p">(</span><span class="mi">4</span><span class="p">,</span> <span class="mi">4</span><span class="p">),</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span> <span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">))</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-60'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-60'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">285</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">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">t</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>
        </div>
    </div>
    <div class='section' id='section-61'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-61'>#</a>
            </div>
            <p><code  class="highlight"><span></span><span class="n">t</span></code>
 is not used, but it&#x27;s kept in the arguments because for the attention layer function signature to match with <code  class="highlight"><span></span><span class="n">ResidualBlock</span></code>
. </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">288</span>        <span class="n">_</span> <span class="o">=</span> <span class="n">t</span>
<span class="lineno">289</span>        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">conv</span><span class="p">(</span><span class="n">x</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-62'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-62'>#</a>
            </div>
            <h3>Scale down the feature map by <span ><span class="katex"><span aria-hidden="true" class="katex-html"><span class="base"><span class="strut" style="height:1.190108em;vertical-align:-0.345em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.845108em;"><span style="top:-2.6550000000000002em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">2</span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.394em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">1</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.345em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mord">×</span></span></span></span></span></h3>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">292</span><span class="k">class</span> <span class="nc">Downsample</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-63'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-63'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">297</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">n_channels</span><span class="p">):</span>
<span class="lineno">298</span>        <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span>
<span class="lineno">299</span>        <span class="bp">self</span><span class="o">.</span><span class="n">conv</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Conv2d</span><span class="p">(</span><span class="n">n_channels</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">,</span> <span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">),</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span> <span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">))</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-64'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-64'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">301</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">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">t</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>
        </div>
    </div>
    <div class='section' id='section-65'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-65'>#</a>
            </div>
            <p><code  class="highlight"><span></span><span class="n">t</span></code>
 is not used, but it&#x27;s kept in the arguments because for the attention layer function signature to match with <code  class="highlight"><span></span><span class="n">ResidualBlock</span></code>
. </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">304</span>        <span class="n">_</span> <span class="o">=</span> <span class="n">t</span>
<span class="lineno">305</span>        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">conv</span><span class="p">(</span><span class="n">x</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-66'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-66'>#</a>
            </div>
            <h2>U-Net</h2>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">308</span><span class="k">class</span> <span class="nc">UNet</span><span class="p">(</span><span class="n">Module</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-67'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-67'>#</a>
            </div>
            <ul><li><code  class="highlight"><span></span><span class="n">image_channels</span></code>
 is the number of channels in the image. <span ><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">3</span></span></span></span></span> for RGB. </li>
<li><code  class="highlight"><span></span><span class="n">n_channels</span></code>
 is number of channels in the initial feature map that we transform the image into </li>
<li><code  class="highlight"><span></span><span class="n">ch_mults</span></code>
 is the list of channel numbers at each resolution. The number of channels is <code  class="highlight"><span></span><span class="n">ch_mults</span><span class="p">[</span><span class="n">i</span><span class="p">]</span> <span class="o">*</span> <span class="n">n_channels</span></code>
 </li>
<li><code  class="highlight"><span></span><span class="n">is_attn</span></code>
 is a list of booleans that indicate whether to use attention at each resolution </li>
<li><code  class="highlight"><span></span><span class="n">n_blocks</span></code>
 is the number of <code  class="highlight"><span></span><span class="n">UpDownBlocks</span></code>
 at each resolution</li></ul>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">313</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">image_channels</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="mi">3</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="mi">64</span><span class="p">,</span>
<span class="lineno">314</span>                 <span class="n">ch_mults</span><span class="p">:</span> <span class="n">Union</span><span class="p">[</span><span class="n">Tuple</span><span class="p">[</span><span class="nb">int</span><span class="p">,</span> <span class="o">...</span><span class="p">],</span> <span class="n">List</span><span class="p">[</span><span class="nb">int</span><span class="p">]]</span> <span class="o">=</span> <span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">4</span><span class="p">),</span>
<span class="lineno">315</span>                 <span class="n">is_attn</span><span class="p">:</span> <span class="n">Union</span><span class="p">[</span><span class="n">Tuple</span><span class="p">[</span><span class="nb">bool</span><span class="p">,</span> <span class="o">...</span><span class="p">],</span> <span class="n">List</span><span class="p">[</span><span class="nb">int</span><span class="p">]]</span> <span class="o">=</span> <span class="p">(</span><span class="kc">False</span><span class="p">,</span> <span class="kc">False</span><span class="p">,</span> <span class="kc">True</span><span class="p">,</span> <span class="kc">True</span><span class="p">),</span>
<span class="lineno">316</span>                 <span class="n">n_blocks</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="mi">2</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-68'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-68'>#</a>
            </div>
            
        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">324</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-69'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-69'>#</a>
            </div>
            <p>Number of resolutions </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">327</span>        <span class="n">n_resolutions</span> <span class="o">=</span> <span class="nb">len</span><span class="p">(</span><span class="n">ch_mults</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-70'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-70'>#</a>
            </div>
            <p>Project image into feature map </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">330</span>        <span class="bp">self</span><span class="o">.</span><span class="n">image_proj</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Conv2d</span><span class="p">(</span><span class="n">image_channels</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">,</span> <span class="n">kernel_size</span><span class="o">=</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">),</span> <span class="n">padding</span><span class="o">=</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">))</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-71'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-71'>#</a>
            </div>
            <p>Time embedding layer. Time embedding has <code  class="highlight"><span></span><span class="n">n_channels</span> <span class="o">*</span> <span class="mi">4</span></code>
 channels </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">333</span>        <span class="bp">self</span><span class="o">.</span><span class="n">time_emb</span> <span class="o">=</span> <span class="n">TimeEmbedding</span><span class="p">(</span><span class="n">n_channels</span> <span class="o">*</span> <span class="mi">4</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-72'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-72'>#</a>
            </div>
            <h4>First half of U-Net - decreasing resolution</h4>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">336</span>        <span class="n">down</span> <span class="o">=</span> <span class="p">[]</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-73'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-73'>#</a>
            </div>
            <p>Number of channels </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">338</span>        <span class="n">out_channels</span> <span class="o">=</span> <span class="n">in_channels</span> <span class="o">=</span> <span class="n">n_channels</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-74'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-74'>#</a>
            </div>
            <p>For each resolution </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">340</span>        <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">n_resolutions</span><span class="p">):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-75'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-75'>#</a>
            </div>
            <p>Number of output channels at this resolution </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">342</span>            <span class="n">out_channels</span> <span class="o">=</span> <span class="n">in_channels</span> <span class="o">*</span> <span class="n">ch_mults</span><span class="p">[</span><span class="n">i</span><span class="p">]</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-76'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-76'>#</a>
            </div>
            <p>Add <code  class="highlight"><span></span><span class="n">n_blocks</span></code>
 </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">344</span>            <span class="k">for</span> <span class="n">_</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">n_blocks</span><span class="p">):</span>
<span class="lineno">345</span>                <span class="n">down</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">DownBlock</span><span class="p">(</span><span class="n">in_channels</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">,</span> <span class="n">n_channels</span> <span class="o">*</span> <span class="mi">4</span><span class="p">,</span> <span class="n">is_attn</span><span class="p">[</span><span class="n">i</span><span class="p">]))</span>
<span class="lineno">346</span>                <span class="n">in_channels</span> <span class="o">=</span> <span class="n">out_channels</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-77'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-77'>#</a>
            </div>
            <p>Down sample at all resolutions except the last </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">348</span>            <span class="k">if</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="n">n_resolutions</span> <span class="o">-</span> <span class="mi">1</span><span class="p">:</span>
<span class="lineno">349</span>                <span class="n">down</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Downsample</span><span class="p">(</span><span class="n">in_channels</span><span class="p">))</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-78'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-78'>#</a>
            </div>
            <p>Combine the set of modules </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">352</span>        <span class="bp">self</span><span class="o">.</span><span class="n">down</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">ModuleList</span><span class="p">(</span><span class="n">down</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-79'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-79'>#</a>
            </div>
            <p>Middle block </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">355</span>        <span class="bp">self</span><span class="o">.</span><span class="n">middle</span> <span class="o">=</span> <span class="n">MiddleBlock</span><span class="p">(</span><span class="n">out_channels</span><span class="p">,</span> <span class="n">n_channels</span> <span class="o">*</span> <span class="mi">4</span><span class="p">,</span> <span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-80'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-80'>#</a>
            </div>
            <h4>Second half of U-Net - increasing resolution</h4>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">358</span>        <span class="n">up</span> <span class="o">=</span> <span class="p">[]</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-81'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-81'>#</a>
            </div>
            <p>Number of channels </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">360</span>        <span class="n">in_channels</span> <span class="o">=</span> <span class="n">out_channels</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-82'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-82'>#</a>
            </div>
            <p>For each resolution </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">362</span>        <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">reversed</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="n">n_resolutions</span><span class="p">)):</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-83'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-83'>#</a>
            </div>
            <p><code  class="highlight"><span></span><span class="n">n_blocks</span></code>
 at the same resolution </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">364</span>            <span class="n">out_channels</span> <span class="o">=</span> <span class="n">in_channels</span>
<span class="lineno">365</span>            <span class="k">for</span> <span class="n">_</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">n_blocks</span><span class="p">):</span>
<span class="lineno">366</span>                <span class="n">up</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">UpBlock</span><span class="p">(</span><span class="n">in_channels</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">,</span> <span class="n">n_channels</span> <span class="o">*</span> <span class="mi">4</span><span class="p">,</span> <span class="n">is_attn</span><span class="p">[</span><span class="n">i</span><span class="p">]))</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-84'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-84'>#</a>
            </div>
            <p>Final block to reduce the number of channels </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">368</span>            <span class="n">out_channels</span> <span class="o">=</span> <span class="n">in_channels</span> <span class="o">//</span> <span class="n">ch_mults</span><span class="p">[</span><span class="n">i</span><span class="p">]</span>
<span class="lineno">369</span>            <span class="n">up</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">UpBlock</span><span class="p">(</span><span class="n">in_channels</span><span class="p">,</span> <span class="n">out_channels</span><span class="p">,</span> <span class="n">n_channels</span> <span class="o">*</span> <span class="mi">4</span><span class="p">,</span> <span class="n">is_attn</span><span class="p">[</span><span class="n">i</span><span class="p">]))</span>
<span class="lineno">370</span>            <span class="n">in_channels</span> <span class="o">=</span> <span class="n">out_channels</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-85'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-85'>#</a>
            </div>
            <p>Up sample at all resolutions except last </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">372</span>            <span class="k">if</span> <span class="n">i</span> <span class="o">&gt;</span> <span class="mi">0</span><span class="p">:</span>
<span class="lineno">373</span>                <span class="n">up</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Upsample</span><span class="p">(</span><span class="n">in_channels</span><span class="p">))</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-86'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-86'>#</a>
            </div>
            <p>Combine the set of modules </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">376</span>        <span class="bp">self</span><span class="o">.</span><span class="n">up</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">ModuleList</span><span class="p">(</span><span class="n">up</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-87'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-87'>#</a>
            </div>
            <p>Final normalization and convolution layer </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">379</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">GroupNorm</span><span class="p">(</span><span class="mi">8</span><span class="p">,</span> <span class="n">n_channels</span><span class="p">)</span>
<span class="lineno">380</span>        <span class="bp">self</span><span class="o">.</span><span class="n">act</span> <span class="o">=</span> <span class="n">Swish</span><span class="p">()</span>
<span class="lineno">381</span>        <span class="bp">self</span><span class="o">.</span><span class="n">final</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">Conv2d</span><span class="p">(</span><span class="n">in_channels</span><span class="p">,</span> <span class="n">image_channels</span><span class="p">,</span> <span class="n">kernel_size</span><span class="o">=</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">),</span> <span class="n">padding</span><span class="o">=</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">))</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-88'>
        <div class='docs doc-strings'>
            <div class='section-link'>
                <a href='#section-88'>#</a>
            </div>
            <ul><li><code  class="highlight"><span></span><span class="n">x</span></code>
 has shape <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">,</span> <span class="n">in_channels</span><span class="p">,</span> <span class="n">height</span><span class="p">,</span> <span class="n">width</span><span class="p">]</span></code>
 </li>
<li><code  class="highlight"><span></span><span class="n">t</span></code>
 has shape <code  class="highlight"><span></span><span class="p">[</span><span class="n">batch_size</span><span class="p">]</span></code>
</li></ul>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">383</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">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">t</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>
        </div>
    </div>
    <div class='section' id='section-89'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-89'>#</a>
            </div>
            <p>Get time-step embeddings </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">390</span>        <span class="n">t</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">time_emb</span><span class="p">(</span><span class="n">t</span><span class="p">)</span></pre></div>
        </div>
    </div>
    <div class='section' id='section-90'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-90'>#</a>
            </div>
            <p>Get image projection </p>

        </div>
        <div class='code'>
            <div class="highlight"><pre><span class="lineno">393</span>        <span class="n">x</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">image_proj</span><span class="p">(</span><span class="n">x</span><span class="p">)</span></pre></div>
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    <div class='section' id='section-91'>
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            <div class='section-link'>
                <a href='#section-91'>#</a>
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            <p><code  class="highlight"><span></span><span class="n">h</span></code>
 will store outputs at each resolution for skip connection </p>

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            <div class="highlight"><pre><span class="lineno">396</span>        <span class="n">h</span> <span class="o">=</span> <span class="p">[</span><span class="n">x</span><span class="p">]</span></pre></div>
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    <div class='section' id='section-92'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-92'>#</a>
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            <p>First half of U-Net </p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">398</span>        <span class="k">for</span> <span class="n">m</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">down</span><span class="p">:</span>
<span class="lineno">399</span>            <span class="n">x</span> <span class="o">=</span> <span class="n">m</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">t</span><span class="p">)</span>
<span class="lineno">400</span>            <span class="n">h</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">x</span><span class="p">)</span></pre></div>
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    </div>
    <div class='section' id='section-93'>
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                <a href='#section-93'>#</a>
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            <p>Middle (bottom) </p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">403</span>        <span class="n">x</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">middle</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">t</span><span class="p">)</span></pre></div>
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    </div>
    <div class='section' id='section-94'>
        <div class='docs'>
            <div class='section-link'>
                <a href='#section-94'>#</a>
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            <p>Second half of U-Net </p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">406</span>        <span class="k">for</span> <span class="n">m</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">up</span><span class="p">:</span>
<span class="lineno">407</span>            <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">m</span><span class="p">,</span> <span class="n">Upsample</span><span class="p">):</span>
<span class="lineno">408</span>                <span class="n">x</span> <span class="o">=</span> <span class="n">m</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">t</span><span class="p">)</span>
<span class="lineno">409</span>            <span class="k">else</span><span class="p">:</span></pre></div>
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    <div class='section' id='section-95'>
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                <a href='#section-95'>#</a>
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            <p>Get the skip connection from first half of U-Net and concatenate </p>

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            <div class="highlight"><pre><span class="lineno">411</span>                <span class="n">s</span> <span class="o">=</span> <span class="n">h</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span>
<span class="lineno">412</span>                <span class="n">x</span> <span class="o">=</span> <span class="n">torch</span><span class="o">.</span><span class="n">cat</span><span class="p">((</span><span class="n">x</span><span class="p">,</span> <span class="n">s</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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    <div class='section' id='section-96'>
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                <a href='#section-96'>#</a>
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            <p> </p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">414</span>                <span class="n">x</span> <span class="o">=</span> <span class="n">m</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">t</span><span class="p">)</span></pre></div>
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    <div class='section' id='section-97'>
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            <div class='section-link'>
                <a href='#section-97'>#</a>
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            <p>Final normalization and convolution </p>

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        <div class='code'>
            <div class="highlight"><pre><span class="lineno">417</span>        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">final</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">act</span><span class="p">(</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>
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