Files
Varuna Jayasiri efd2673735 cleanup
2021-06-02 21:40:05 +05:30

349 lines
24 KiB
HTML

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=utf-8"/>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<meta name="description" content="A simple PyTorch implementation/tutorial of Generative Adversarial Networks (GAN) loss functions."/>
<meta name="twitter:card" content="summary"/>
<meta name="twitter:image:src" content="https://avatars1.githubusercontent.com/u/64068543?s=400&amp;v=4"/>
<meta name="twitter:title" content="Generative Adversarial Networks (GAN)"/>
<meta name="twitter:description" content="A simple PyTorch implementation/tutorial of Generative Adversarial Networks (GAN) loss functions."/>
<meta name="twitter:site" content="@labmlai"/>
<meta name="twitter:creator" content="@labmlai"/>
<meta property="og:url" content="https://nn.labml.ai/gan/original/index.html"/>
<meta property="og:title" content="Generative Adversarial Networks (GAN)"/>
<meta property="og:image" content="https://avatars1.githubusercontent.com/u/64068543?s=400&amp;v=4"/>
<meta property="og:site_name" content="LabML Neural Networks"/>
<meta property="og:type" content="object"/>
<meta property="og:title" content="Generative Adversarial Networks (GAN)"/>
<meta property="og:description" content="A simple PyTorch implementation/tutorial of Generative Adversarial Networks (GAN) loss functions."/>
<title>Generative Adversarial Networks (GAN)</title>
<link rel="shortcut icon" href="/icon.png"/>
<link rel="stylesheet" href="../../pylit.css">
<link rel="canonical" href="https://nn.labml.ai/gan/original/index.html"/>
<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=G-4V3HC8HBLH"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag() {
dataLayer.push(arguments);
}
gtag('js', new Date());
gtag('config', 'G-4V3HC8HBLH');
</script>
</head>
<body>
<div id='container'>
<div id="background"></div>
<div class='section'>
<div class='docs'>
<p>
<a class="parent" href="/">home</a>
<a class="parent" href="../index.html">gan</a>
<a class="parent" href="index.html">original</a>
</p>
<p>
<a href="https://github.com/lab-ml/labml_nn/tree/master/labml_nn/gan/original/__init__.py">
<img alt="Github"
src="https://img.shields.io/github/stars/lab-ml/nn?style=social"
style="max-width:100%;"/></a>
<a href="https://twitter.com/labmlai"
rel="nofollow">
<img alt="Twitter"
src="https://img.shields.io/twitter/follow/labmlai?style=social"
style="max-width:100%;"/></a>
</p>
</div>
</div>
<div class='section' id='section-0'>
<div class='docs doc-strings'>
<div class='section-link'>
<a href='#section-0'>#</a>
</div>
<h1>Generative Adversarial Networks (GAN)</h1>
<p>This is an implementation of
<a href="https://arxiv.org/abs/1406.2661">Generative Adversarial Networks</a>.</p>
<p>The generator, $G(\pmb{z}; \theta_g)$ generates samples that match the
distribution of data, while the discriminator, $D(\pmb{x}; \theta_g)$
gives the probability that $\pmb{x}$ came from data rather than $G$.</p>
<p>We train $D$ and $G$ simultaneously on a two-player min-max game with value
function $V(G, D)$.</p>
<p>
<script type="math/tex; mode=display">\min_G \max_D V(D, G) =
\mathop{\mathbb{E}}_{\pmb{x} \sim p_{data}(\pmb{x})}
\big[\log D(\pmb{x})\big] +
\mathop{\mathbb{E}}_{\pmb{z} \sim p_{\pmb{z}}(\pmb{z})}
\big[\log (1 - D(G(\pmb{z}))\big]
</script>
</p>
<p>$p_{data}(\pmb{x})$ is the probability distribution over data,
whilst $p_{\pmb{z}}(\pmb{z})$ probability distribution of $\pmb{z}$, which is set to
gaussian noise.</p>
<p>This file defines the loss functions. <a href="../simple_mnist_experiment.html">Here</a> is an MNIST example
with two multilayer perceptron for the generator and discriminator.</p>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">34</span><span></span><span class="kn">import</span> <span class="nn">torch</span>
<span class="lineno">35</span><span class="kn">import</span> <span class="nn">torch.nn</span> <span class="k">as</span> <span class="nn">nn</span>
<span class="lineno">36</span><span class="kn">import</span> <span class="nn">torch.utils.data</span>
<span class="lineno">37</span><span class="kn">import</span> <span class="nn">torch.utils.data</span>
<span class="lineno">38</span>
<span class="lineno">39</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>
</div>
</div>
<div class='section' id='section-1'>
<div class='docs doc-strings'>
<div class='section-link'>
<a href='#section-1'>#</a>
</div>
<h2>Discriminator Loss</h2>
<p>Discriminator should <strong>ascend</strong> on the gradient,</p>
<p>
<script type="math/tex; mode=display">\nabla_{\theta_d} \frac{1}{m} \sum_{i=1}^m \Bigg[
\log D\Big(\pmb{x}^{(i)}\Big) +
\log \Big(1 - D\Big(G\Big(\pmb{z}^{(i)}\Big)\Big)\Big)
\Bigg]</script>
</p>
<p>$m$ is the mini-batch size and $(i)$ is used to index samples in the mini-batch.
$\pmb{x}$ are samples from $p_{data}$ and $\pmb{z}$ are samples from $p_z$.</p>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">42</span><span class="k">class</span> <span class="nc">DiscriminatorLogitsLoss</span><span class="p">(</span><span class="n">Module</span><span class="p">):</span></pre></div>
</div>
</div>
<div class='section' id='section-2'>
<div class='docs'>
<div class='section-link'>
<a href='#section-2'>#</a>
</div>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">57</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">smoothing</span><span class="p">:</span> <span class="nb">float</span> <span class="o">=</span> <span class="mf">0.2</span><span class="p">):</span>
<span class="lineno">58</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-3'>
<div class='docs'>
<div class='section-link'>
<a href='#section-3'>#</a>
</div>
<p>We use PyTorch Binary Cross Entropy Loss, which is
$-\sum\Big[y \log(\hat{y}) + (1 - y) \log(1 - \hat{y})\Big]$,
where $y$ are the labels and $\hat{y}$ are the predictions.
<em>Note the negative sign</em>.
We use labels equal to $1$ for $\pmb{x}$ from $p_{data}$
and labels equal to $0$ for $\pmb{x}$ from $p_{G}.$
Then descending on the sum of these is the same as ascending on
the above gradient.</p>
<p><code>BCEWithLogitsLoss</code> combines softmax and binary cross entropy loss.</p>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">69</span> <span class="bp">self</span><span class="o">.</span><span class="n">loss_true</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">BCEWithLogitsLoss</span><span class="p">()</span>
<span class="lineno">70</span> <span class="bp">self</span><span class="o">.</span><span class="n">loss_false</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">BCEWithLogitsLoss</span><span class="p">()</span></pre></div>
</div>
</div>
<div class='section' id='section-4'>
<div class='docs'>
<div class='section-link'>
<a href='#section-4'>#</a>
</div>
<p>We use label smoothing because it seems to work better in some cases</p>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">73</span> <span class="bp">self</span><span class="o">.</span><span class="n">smoothing</span> <span class="o">=</span> <span class="n">smoothing</span></pre></div>
</div>
</div>
<div class='section' id='section-5'>
<div class='docs'>
<div class='section-link'>
<a href='#section-5'>#</a>
</div>
<p>Labels are registered as buffered and persistence is set to <code>False</code>.</p>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">76</span> <span class="bp">self</span><span class="o">.</span><span class="n">register_buffer</span><span class="p">(</span><span class="s1">&#39;labels_true&#39;</span><span class="p">,</span> <span class="n">_create_labels</span><span class="p">(</span><span class="mi">256</span><span class="p">,</span> <span class="mf">1.0</span> <span class="o">-</span> <span class="n">smoothing</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">),</span> <span class="kc">False</span><span class="p">)</span>
<span class="lineno">77</span> <span class="bp">self</span><span class="o">.</span><span class="n">register_buffer</span><span class="p">(</span><span class="s1">&#39;labels_false&#39;</span><span class="p">,</span> <span class="n">_create_labels</span><span class="p">(</span><span class="mi">256</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="n">smoothing</span><span class="p">),</span> <span class="kc">False</span><span class="p">)</span></pre></div>
</div>
</div>
<div class='section' id='section-6'>
<div class='docs doc-strings'>
<div class='section-link'>
<a href='#section-6'>#</a>
</div>
<p><code>logits_true</code> are logits from $D(\pmb{x}^{(i)})$ and
<code>logits_false</code> are logits from $D(G(\pmb{z}^{(i)}))$</p>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">79</span> <span class="k">def</span> <span class="fm">__call__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">logits_true</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">logits_false</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-7'>
<div class='docs'>
<div class='section-link'>
<a href='#section-7'>#</a>
</div>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">84</span> <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">logits_true</span><span class="p">)</span> <span class="o">&gt;</span> <span class="nb">len</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">labels_true</span><span class="p">):</span>
<span class="lineno">85</span> <span class="bp">self</span><span class="o">.</span><span class="n">register_buffer</span><span class="p">(</span><span class="s2">&quot;labels_true&quot;</span><span class="p">,</span>
<span class="lineno">86</span> <span class="n">_create_labels</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">logits_true</span><span class="p">),</span> <span class="mf">1.0</span> <span class="o">-</span> <span class="bp">self</span><span class="o">.</span><span class="n">smoothing</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">,</span> <span class="n">logits_true</span><span class="o">.</span><span class="n">device</span><span class="p">),</span> <span class="kc">False</span><span class="p">)</span>
<span class="lineno">87</span> <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">logits_false</span><span class="p">)</span> <span class="o">&gt;</span> <span class="nb">len</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">labels_false</span><span class="p">):</span>
<span class="lineno">88</span> <span class="bp">self</span><span class="o">.</span><span class="n">register_buffer</span><span class="p">(</span><span class="s2">&quot;labels_false&quot;</span><span class="p">,</span>
<span class="lineno">89</span> <span class="n">_create_labels</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">logits_false</span><span class="p">),</span> <span class="mf">0.0</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">smoothing</span><span class="p">,</span> <span class="n">logits_false</span><span class="o">.</span><span class="n">device</span><span class="p">),</span> <span class="kc">False</span><span class="p">)</span>
<span class="lineno">90</span>
<span class="lineno">91</span> <span class="k">return</span> <span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">loss_true</span><span class="p">(</span><span class="n">logits_true</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">labels_true</span><span class="p">[:</span><span class="nb">len</span><span class="p">(</span><span class="n">logits_true</span><span class="p">)]),</span>
<span class="lineno">92</span> <span class="bp">self</span><span class="o">.</span><span class="n">loss_false</span><span class="p">(</span><span class="n">logits_false</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">labels_false</span><span class="p">[:</span><span class="nb">len</span><span class="p">(</span><span class="n">logits_false</span><span class="p">)]))</span></pre></div>
</div>
</div>
<div class='section' id='section-8'>
<div class='docs doc-strings'>
<div class='section-link'>
<a href='#section-8'>#</a>
</div>
<h2>Generator Loss</h2>
<p>Generator should <strong>descend</strong> on the gradient,</p>
<p>
<script type="math/tex; mode=display">\nabla_{\theta_g} \frac{1}{m} \sum_{i=1}^m \Bigg[
\log \Big(1 - D\Big(G\Big(\pmb{z}^{(i)}\Big)\Big)\Big)
\Bigg]</script>
</p>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">95</span><span class="k">class</span> <span class="nc">GeneratorLogitsLoss</span><span class="p">(</span><span class="n">Module</span><span class="p">):</span></pre></div>
</div>
</div>
<div class='section' id='section-9'>
<div class='docs'>
<div class='section-link'>
<a href='#section-9'>#</a>
</div>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">105</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">smoothing</span><span class="p">:</span> <span class="nb">float</span> <span class="o">=</span> <span class="mf">0.2</span><span class="p">):</span>
<span class="lineno">106</span> <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span>
<span class="lineno">107</span> <span class="bp">self</span><span class="o">.</span><span class="n">loss_true</span> <span class="o">=</span> <span class="n">nn</span><span class="o">.</span><span class="n">BCEWithLogitsLoss</span><span class="p">()</span>
<span class="lineno">108</span> <span class="bp">self</span><span class="o">.</span><span class="n">smoothing</span> <span class="o">=</span> <span class="n">smoothing</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>We use labels equal to $1$ for $\pmb{x}$ from $p_{G}.$
Then descending on this loss is the same as descending on
the above gradient.</p>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">112</span> <span class="bp">self</span><span class="o">.</span><span class="n">register_buffer</span><span class="p">(</span><span class="s1">&#39;fake_labels&#39;</span><span class="p">,</span> <span class="n">_create_labels</span><span class="p">(</span><span class="mi">256</span><span class="p">,</span> <span class="mf">1.0</span> <span class="o">-</span> <span class="n">smoothing</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">),</span> <span class="kc">False</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>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">114</span> <span class="k">def</span> <span class="fm">__call__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">logits</span><span class="p">:</span> <span class="n">torch</span><span class="o">.</span><span class="n">Tensor</span><span class="p">):</span>
<span class="lineno">115</span> <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">logits</span><span class="p">)</span> <span class="o">&gt;</span> <span class="nb">len</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">fake_labels</span><span class="p">):</span>
<span class="lineno">116</span> <span class="bp">self</span><span class="o">.</span><span class="n">register_buffer</span><span class="p">(</span><span class="s2">&quot;fake_labels&quot;</span><span class="p">,</span>
<span class="lineno">117</span> <span class="n">_create_labels</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">logits</span><span class="p">),</span> <span class="mf">1.0</span> <span class="o">-</span> <span class="bp">self</span><span class="o">.</span><span class="n">smoothing</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">,</span> <span class="n">logits</span><span class="o">.</span><span class="n">device</span><span class="p">),</span> <span class="kc">False</span><span class="p">)</span>
<span class="lineno">118</span>
<span class="lineno">119</span> <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">loss_true</span><span class="p">(</span><span class="n">logits</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">fake_labels</span><span class="p">[:</span><span class="nb">len</span><span class="p">(</span><span class="n">logits</span><span class="p">)])</span></pre></div>
</div>
</div>
<div class='section' id='section-12'>
<div class='docs doc-strings'>
<div class='section-link'>
<a href='#section-12'>#</a>
</div>
<p>Create smoothed labels</p>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">122</span><span class="k">def</span> <span class="nf">_create_labels</span><span class="p">(</span><span class="n">n</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">r1</span><span class="p">:</span> <span class="nb">float</span><span class="p">,</span> <span class="n">r2</span><span class="p">:</span> <span class="nb">float</span><span class="p">,</span> <span class="n">device</span><span class="p">:</span> <span class="n">torch</span><span class="o">.</span><span class="n">device</span> <span class="o">=</span> <span class="kc">None</span><span class="p">):</span></pre></div>
</div>
</div>
<div class='section' id='section-13'>
<div class='docs'>
<div class='section-link'>
<a href='#section-13'>#</a>
</div>
</div>
<div class='code'>
<div class="highlight"><pre><span class="lineno">126</span> <span class="k">return</span> <span class="n">torch</span><span class="o">.</span><span class="n">empty</span><span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">requires_grad</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="n">device</span><span class="o">=</span><span class="n">device</span><span class="p">)</span><span class="o">.</span><span class="n">uniform_</span><span class="p">(</span><span class="n">r1</span><span class="p">,</span> <span class="n">r2</span><span class="p">)</span></pre></div>
</div>
</div>
</div>
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.4/MathJax.js?config=TeX-AMS_HTML">
</script>
<!-- MathJax configuration -->
<script type="text/x-mathjax-config">
MathJax.Hub.Config({
tex2jax: {
inlineMath: [ ['$','$'] ],
displayMath: [ ['$$','$$'] ],
processEscapes: true,
processEnvironments: true
},
// Center justify equations in code and markdown cells. Elsewhere
// we use CSS to left justify single line equations in code cells.
displayAlign: 'center',
"HTML-CSS": { fonts: ["TeX"] }
});
</script>
<script>
function handleImages() {
var images = document.querySelectorAll('p>img')
console.log(images);
for (var i = 0; i < images.length; ++i) {
handleImage(images[i])
}
}
function handleImage(img) {
img.parentElement.style.textAlign = 'center'
var modal = document.createElement('div')
modal.id = 'modal'
var modalContent = document.createElement('div')
modal.appendChild(modalContent)
var modalImage = document.createElement('img')
modalContent.appendChild(modalImage)
var span = document.createElement('span')
span.classList.add('close')
span.textContent = 'x'
modal.appendChild(span)
img.onclick = function () {
console.log('clicked')
document.body.appendChild(modal)
modalImage.src = img.src
}
span.onclick = function () {
document.body.removeChild(modal)
}
}
handleImages()
</script>
</body>
</html>