401 lines
25 KiB
HTML
401 lines
25 KiB
HTML
<!--
|
|
Automatically generated HTML file from DocOnce source
|
|
(https://github.com/hplgit/doconce/)
|
|
-->
|
|
<html>
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<meta name="generator" content="DocOnce: https://github.com/hplgit/doconce/" />
|
|
<meta name="description" content="Data Analysis and Machine Learning: Neural networks, from the simple perceptron to deep learning">
|
|
|
|
<title>Data Analysis and Machine Learning: Neural networks, from the simple perceptron to deep learning</title>
|
|
|
|
<!-- Bootstrap style: bootstrap -->
|
|
<link href="https://netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css" rel="stylesheet">
|
|
<!-- not necessary
|
|
<link href="https://netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.css" rel="stylesheet">
|
|
-->
|
|
|
|
<style type="text/css">
|
|
|
|
/* Add scrollbar to dropdown menus in bootstrap navigation bar */
|
|
.dropdown-menu {
|
|
height: auto;
|
|
max-height: 400px;
|
|
overflow-x: hidden;
|
|
}
|
|
|
|
/* Adds an invisible element before each target to offset for the navigation
|
|
bar */
|
|
.anchor::before {
|
|
content:"";
|
|
display:block;
|
|
height:50px; /* fixed header height for style bootstrap */
|
|
margin:-50px 0 0; /* negative fixed header height */
|
|
}
|
|
</style>
|
|
|
|
|
|
</head>
|
|
|
|
<!-- tocinfo
|
|
{'highest level': 2,
|
|
'sections': [('Neural networks', 2, None, '___sec0'),
|
|
('Artificial neurons', 2, None, '___sec1'),
|
|
('Neural network types', 2, None, '___sec2'),
|
|
('Feed-forward neural networks', 2, None, '___sec3'),
|
|
('Convolutional Neural Network', 2, None, '___sec4'),
|
|
('Recurrent neural networks', 2, None, '___sec5'),
|
|
('Other types of networks', 2, None, '___sec6'),
|
|
('Multilayer perceptrons', 2, None, '___sec7'),
|
|
('Why multilayer perceptrons?', 2, None, '___sec8'),
|
|
('Mathematical model', 2, None, '___sec9'),
|
|
('Mathematical model', 2, None, '___sec10'),
|
|
('Mathematical model', 2, None, '___sec11'),
|
|
('Mathematical model', 2, None, '___sec12'),
|
|
('Mathematical model', 2, None, '___sec13'),
|
|
('Matrix-vector notation', 3, None, '___sec14'),
|
|
('Matrix-vector notation and activation', 3, None, '___sec15'),
|
|
('Activation functions', 3, None, '___sec16'),
|
|
('Activation functions, Logistic and Hyperbolic ones',
|
|
3,
|
|
None,
|
|
'___sec17'),
|
|
('Relevance', 3, None, '___sec18'),
|
|
('The multilayer perceptron (MLP)', 2, None, '___sec19'),
|
|
('From one to many layers, the universal approximation theorem',
|
|
2,
|
|
None,
|
|
'___sec20'),
|
|
('Deriving the back propagation code for a multilayer perceptron '
|
|
'model',
|
|
2,
|
|
None,
|
|
'___sec21'),
|
|
('Definitions', 2, None, '___sec22'),
|
|
('Derivatives and the chain rule', 2, None, '___sec23'),
|
|
('Derivative of the cost function', 2, None, '___sec24'),
|
|
('Bringing it together, first back propagation equation',
|
|
2,
|
|
None,
|
|
'___sec25'),
|
|
('Derivatives in terms of $z_j^L$', 2, None, '___sec26'),
|
|
('Bringing it together', 2, None, '___sec27'),
|
|
('Final back propagating equation', 2, None, '___sec28'),
|
|
('Setting up the Back propagation algorithm',
|
|
2,
|
|
None,
|
|
'___sec29'),
|
|
('Setting up a Multi-layer perceptron model for classification',
|
|
2,
|
|
None,
|
|
'___sec30'),
|
|
('Defining the cost function', 2, None, '___sec31'),
|
|
('Developing a code for doing neural networks with back '
|
|
'propagation',
|
|
2,
|
|
None,
|
|
'___sec32'),
|
|
('Collect and pre-process data', 2, None, '___sec33'),
|
|
('Train and test datasets', 2, None, '___sec34'),
|
|
('Define model and architecture', 2, None, '___sec35'),
|
|
('Layers', 2, None, '___sec36'),
|
|
('Weights and biases', 2, None, '___sec37'),
|
|
('Feed-forward pass', 2, None, '___sec38'),
|
|
('Matrix multiplication', 2, None, '___sec39'),
|
|
('Choose cost function and optimizer', 2, None, '___sec40'),
|
|
('Optimizing the cost function', 2, None, '___sec41'),
|
|
('Regularization', 2, None, '___sec42'),
|
|
('Matrix multiplication', 2, None, '___sec43'),
|
|
('Improving performance', 2, None, '___sec44'),
|
|
('Full object-oriented implementation', 2, None, '___sec45'),
|
|
('Evaluate model performance on test data', 2, None, '___sec46'),
|
|
('Adjust hyperparameters', 2, None, '___sec47'),
|
|
('Visualization', 2, None, '___sec48'),
|
|
('scikit-learn implementation', 2, None, '___sec49'),
|
|
('Visualization', 2, None, '___sec50'),
|
|
('Building neural networks in Tensorflow and Keras',
|
|
2,
|
|
None,
|
|
'___sec51'),
|
|
('Tensorflow', 2, None, '___sec52'),
|
|
('Collect and pre-process data', 2, None, '___sec53'),
|
|
('Using TensorFlow backend', 2, None, '___sec54'),
|
|
('Optimizing and using gradient descent', 2, None, '___sec55'),
|
|
('Using Keras', 2, None, '___sec56')]}
|
|
end of tocinfo -->
|
|
|
|
<body>
|
|
|
|
|
|
|
|
<script type="text/x-mathjax-config">
|
|
MathJax.Hub.Config({
|
|
TeX: {
|
|
equationNumbers: { autoNumber: "none" },
|
|
extensions: ["AMSmath.js", "AMSsymbols.js", "autobold.js", "color.js"]
|
|
}
|
|
});
|
|
</script>
|
|
<script type="text/javascript" async
|
|
src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
|
|
</script>
|
|
|
|
|
|
|
|
|
|
<!-- Bootstrap navigation bar -->
|
|
<div class="navbar navbar-default navbar-fixed-top">
|
|
<div class="navbar-header">
|
|
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-responsive-collapse">
|
|
<span class="icon-bar"></span>
|
|
<span class="icon-bar"></span>
|
|
<span class="icon-bar"></span>
|
|
</button>
|
|
<a class="navbar-brand" href="NeuralNet-bs.html">Data Analysis and Machine Learning: Neural networks, from the simple perceptron to deep learning</a>
|
|
</div>
|
|
|
|
<div class="navbar-collapse collapse navbar-responsive-collapse">
|
|
<ul class="nav navbar-nav navbar-right">
|
|
<li class="dropdown">
|
|
<a href="#" class="dropdown-toggle" data-toggle="dropdown">Contents <b class="caret"></b></a>
|
|
<ul class="dropdown-menu">
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs001.html#___sec0" style="font-size: 80%;"><b>Neural networks</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs002.html#___sec1" style="font-size: 80%;"><b>Artificial neurons</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs003.html#___sec2" style="font-size: 80%;"><b>Neural network types</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs004.html#___sec3" style="font-size: 80%;"><b>Feed-forward neural networks</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs005.html#___sec4" style="font-size: 80%;"><b>Convolutional Neural Network</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs006.html#___sec5" style="font-size: 80%;"><b>Recurrent neural networks</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs007.html#___sec6" style="font-size: 80%;"><b>Other types of networks</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs008.html#___sec7" style="font-size: 80%;"><b>Multilayer perceptrons</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs009.html#___sec8" style="font-size: 80%;"><b>Why multilayer perceptrons?</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs010.html#___sec9" style="font-size: 80%;"><b>Mathematical model</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs011.html#___sec10" style="font-size: 80%;"><b>Mathematical model</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs012.html#___sec11" style="font-size: 80%;"><b>Mathematical model</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs013.html#___sec12" style="font-size: 80%;"><b>Mathematical model</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs014.html#___sec13" style="font-size: 80%;"><b>Mathematical model</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs015.html#___sec14" style="font-size: 80%;"> Matrix-vector notation</a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs016.html#___sec15" style="font-size: 80%;"> Matrix-vector notation and activation</a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs017.html#___sec16" style="font-size: 80%;"> Activation functions</a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs018.html#___sec17" style="font-size: 80%;"> Activation functions, Logistic and Hyperbolic ones</a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs019.html#___sec18" style="font-size: 80%;"> Relevance</a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs020.html#___sec19" style="font-size: 80%;"><b>The multilayer perceptron (MLP)</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs021.html#___sec20" style="font-size: 80%;"><b>From one to many layers, the universal approximation theorem</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs022.html#___sec21" style="font-size: 80%;"><b>Deriving the back propagation code for a multilayer perceptron model</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs023.html#___sec22" style="font-size: 80%;"><b>Definitions</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs024.html#___sec23" style="font-size: 80%;"><b>Derivatives and the chain rule</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs025.html#___sec24" style="font-size: 80%;"><b>Derivative of the cost function</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs026.html#___sec25" style="font-size: 80%;"><b>Bringing it together, first back propagation equation</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs027.html#___sec26" style="font-size: 80%;"><b>Derivatives in terms of \( z_j^L \)</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs028.html#___sec27" style="font-size: 80%;"><b>Bringing it together</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs029.html#___sec28" style="font-size: 80%;"><b>Final back propagating equation</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs030.html#___sec29" style="font-size: 80%;"><b>Setting up the Back propagation algorithm</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs031.html#___sec30" style="font-size: 80%;"><b>Setting up a Multi-layer perceptron model for classification</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs032.html#___sec31" style="font-size: 80%;"><b>Defining the cost function</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs033.html#___sec32" style="font-size: 80%;"><b>Developing a code for doing neural networks with back propagation</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs034.html#___sec33" style="font-size: 80%;"><b>Collect and pre-process data</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs035.html#___sec34" style="font-size: 80%;"><b>Train and test datasets</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs036.html#___sec35" style="font-size: 80%;"><b>Define model and architecture</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs037.html#___sec36" style="font-size: 80%;"><b>Layers</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs038.html#___sec37" style="font-size: 80%;"><b>Weights and biases</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs039.html#___sec38" style="font-size: 80%;"><b>Feed-forward pass</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs040.html#___sec39" style="font-size: 80%;"><b>Matrix multiplication</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs041.html#___sec40" style="font-size: 80%;"><b>Choose cost function and optimizer</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs042.html#___sec41" style="font-size: 80%;"><b>Optimizing the cost function</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs043.html#___sec42" style="font-size: 80%;"><b>Regularization</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="#___sec43" style="font-size: 80%;"><b>Matrix multiplication</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs045.html#___sec44" style="font-size: 80%;"><b>Improving performance</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs046.html#___sec45" style="font-size: 80%;"><b>Full object-oriented implementation</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs047.html#___sec46" style="font-size: 80%;"><b>Evaluate model performance on test data</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs048.html#___sec47" style="font-size: 80%;"><b>Adjust hyperparameters</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs049.html#___sec48" style="font-size: 80%;"><b>Visualization</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs050.html#___sec49" style="font-size: 80%;"><b>scikit-learn implementation</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs051.html#___sec50" style="font-size: 80%;"><b>Visualization</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs052.html#___sec51" style="font-size: 80%;"><b>Building neural networks in Tensorflow and Keras</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs053.html#___sec52" style="font-size: 80%;"><b>Tensorflow</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs054.html#___sec53" style="font-size: 80%;"><b>Collect and pre-process data</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs055.html#___sec54" style="font-size: 80%;"><b>Using TensorFlow backend</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs056.html#___sec55" style="font-size: 80%;"><b>Optimizing and using gradient descent</b></a></li>
|
|
<!-- navigation toc: --> <li><a href="._NeuralNet-bs057.html#___sec56" style="font-size: 80%;"><b>Using Keras</b></a></li>
|
|
|
|
</ul>
|
|
</li>
|
|
</ul>
|
|
</div>
|
|
</div>
|
|
</div> <!-- end of navigation bar -->
|
|
|
|
<div class="container">
|
|
|
|
<p> </p><p> </p><p> </p> <!-- add vertical space -->
|
|
|
|
<a name="part0044"></a>
|
|
<!-- !split -->
|
|
|
|
<h2 id="___sec43" class="anchor">Matrix multiplication </h2>
|
|
|
|
<p>
|
|
To more efficently train our network these equations are implemented using matrix operations.
|
|
The error in the output layer is calculated simply as
|
|
|
|
$$ \delta_L = \hat{y} - y = (n_{inputs}, n_{categories}) .$$
|
|
|
|
<p>
|
|
The gradient for the output weights is calculated as
|
|
|
|
$$ \nabla W_{L} = \hat{a}^T \delta_L = (n_{hidden}, n_{categories}) ,$$
|
|
|
|
<p>
|
|
where \( \hat{a} = (n_{inputs}, n_{hidden}) \). This simply means that we are summing up the gradients for each input.
|
|
Since we are going backwards we have to transpose the activation matrix.
|
|
|
|
<p>
|
|
The gradient with respect to the output bias is then
|
|
|
|
$$ \nabla \hat{b}_{L} = \sum_{i=1}^{n_{inputs}} \delta_L = (n_{categories}) .$$
|
|
|
|
<p>
|
|
The error in the hidden layer is
|
|
|
|
$$ \Delta_h = \delta_L W_{L}^T \circ f'(z_{h}) = \delta_L W_{L}^T \circ a_{h} \circ (1 - a_{h}) = (n_{inputs}, n_{hidden}) ,$$
|
|
|
|
<p>
|
|
where \( f'(a_{h}) \) is the derivative of the activation in the hidden layer. The matrix products mean
|
|
that we are summing up the products for each neuron in the output layer. The symbol \( \circ \) denotes
|
|
the <em>Hadamard product</em>, meaning element-wise multiplication.
|
|
|
|
<p>
|
|
This again gives us the gradients in the hidden layer:
|
|
|
|
$$ \nabla W_{h} = X^T \delta_h = (n_{features}, n_{hidden}) ,$$
|
|
|
|
$$ \nabla b_{h} = \sum_{i=1}^{n_{inputs}} \delta_h = (n_{hidden}) .$$
|
|
|
|
<p>
|
|
|
|
<!-- code=python (!bc pycod) typeset with pygments style "default" -->
|
|
<div class="highlight" style="background: #f8f8f8"><pre style="line-height: 125%"><span></span><span style="color: #408080; font-style: italic"># to categorical turns our integer vector into a onehot representation</span>
|
|
<span style="color: #408080; font-style: italic">#from keras.utils import to_categorical</span>
|
|
|
|
<span style="color: #408080; font-style: italic"># calculate the accuracy score of our model</span>
|
|
<span style="color: #008000; font-weight: bold">from</span> <span style="color: #0000FF; font-weight: bold">sklearn.metrics</span> <span style="color: #008000; font-weight: bold">import</span> accuracy_score
|
|
|
|
<span style="color: #408080; font-style: italic"># one-hot in numpy</span>
|
|
<span style="color: #008000; font-weight: bold">def</span> <span style="color: #0000FF">to_categorical_numpy</span>(integer_vector):
|
|
n_inputs <span style="color: #666666">=</span> <span style="color: #008000">len</span>(integer_vector)
|
|
n_categories <span style="color: #666666">=</span> np<span style="color: #666666">.</span>max(integer_vector) <span style="color: #666666">+</span> <span style="color: #666666">1</span>
|
|
onehot_vector <span style="color: #666666">=</span> np<span style="color: #666666">.</span>zeros((n_inputs, n_categories))
|
|
onehot_vector[<span style="color: #008000">range</span>(n_inputs), integer_vector] <span style="color: #666666">=</span> <span style="color: #666666">1</span>
|
|
|
|
<span style="color: #008000; font-weight: bold">return</span> onehot_vector
|
|
|
|
<span style="color: #408080; font-style: italic">#Y_train_onehot, Y_test_onehot = to_categorical(Y_train), to_categorical(Y_test)</span>
|
|
Y_train_onehot, Y_test_onehot <span style="color: #666666">=</span> to_categorical_numpy(Y_train), to_categorical_numpy(Y_test)
|
|
|
|
<span style="color: #008000; font-weight: bold">def</span> <span style="color: #0000FF">feed_forward_train</span>(X):
|
|
<span style="color: #408080; font-style: italic"># weighted sum of inputs to the hidden layer</span>
|
|
z_h <span style="color: #666666">=</span> np<span style="color: #666666">.</span>matmul(X, hidden_weights) <span style="color: #666666">+</span> hidden_bias
|
|
<span style="color: #408080; font-style: italic"># activation in the hidden layer</span>
|
|
a_h <span style="color: #666666">=</span> sigmoid(z_h)
|
|
|
|
<span style="color: #408080; font-style: italic"># weighted sum of inputs to the output layer</span>
|
|
z_o <span style="color: #666666">=</span> np<span style="color: #666666">.</span>matmul(a_h, output_weights) <span style="color: #666666">+</span> output_bias
|
|
<span style="color: #408080; font-style: italic"># softmax output</span>
|
|
<span style="color: #408080; font-style: italic"># axis 0 holds each input and axis 1 the probabilities of each category</span>
|
|
exp_term <span style="color: #666666">=</span> np<span style="color: #666666">.</span>exp(z_o)
|
|
probabilities <span style="color: #666666">=</span> exp_term <span style="color: #666666">/</span> np<span style="color: #666666">.</span>sum(exp_term, axis<span style="color: #666666">=1</span>, keepdims<span style="color: #666666">=</span><span style="color: #008000">True</span>)
|
|
|
|
<span style="color: #408080; font-style: italic"># for backpropagation need activations in hidden and output layers</span>
|
|
<span style="color: #008000; font-weight: bold">return</span> a_h, probabilities
|
|
|
|
<span style="color: #008000; font-weight: bold">def</span> <span style="color: #0000FF">backpropagation</span>(X, Y):
|
|
a_h, probabilities <span style="color: #666666">=</span> feed_forward_train(X)
|
|
|
|
<span style="color: #408080; font-style: italic"># error in the output layer</span>
|
|
error_output <span style="color: #666666">=</span> probabilities <span style="color: #666666">-</span> Y
|
|
<span style="color: #408080; font-style: italic"># error in the hidden layer</span>
|
|
error_hidden <span style="color: #666666">=</span> np<span style="color: #666666">.</span>matmul(error_output, output_weights<span style="color: #666666">.</span>T) <span style="color: #666666">*</span> a_h <span style="color: #666666">*</span> (<span style="color: #666666">1</span> <span style="color: #666666">-</span> a_h)
|
|
|
|
<span style="color: #408080; font-style: italic"># gradients for the output layer</span>
|
|
output_weights_gradient <span style="color: #666666">=</span> np<span style="color: #666666">.</span>matmul(a_h<span style="color: #666666">.</span>T, error_output)
|
|
output_bias_gradient <span style="color: #666666">=</span> np<span style="color: #666666">.</span>sum(error_output, axis<span style="color: #666666">=0</span>)
|
|
|
|
<span style="color: #408080; font-style: italic"># gradient for the hidden layer</span>
|
|
hidden_weights_gradient <span style="color: #666666">=</span> np<span style="color: #666666">.</span>matmul(X<span style="color: #666666">.</span>T, error_hidden)
|
|
hidden_bias_gradient <span style="color: #666666">=</span> np<span style="color: #666666">.</span>sum(error_hidden, axis<span style="color: #666666">=0</span>)
|
|
|
|
<span style="color: #008000; font-weight: bold">return</span> output_weights_gradient, output_bias_gradient, hidden_weights_gradient, hidden_bias_gradient
|
|
|
|
<span style="color: #008000; font-weight: bold">print</span>(<span style="color: #BA2121">"Old accuracy on training data: "</span> <span style="color: #666666">+</span> <span style="color: #008000">str</span>(accuracy_score(predict(X_train), Y_train)))
|
|
|
|
eta <span style="color: #666666">=</span> <span style="color: #666666">0.01</span>
|
|
lmbd <span style="color: #666666">=</span> <span style="color: #666666">0.01</span>
|
|
<span style="color: #008000; font-weight: bold">for</span> i <span style="color: #AA22FF; font-weight: bold">in</span> <span style="color: #008000">range</span>(<span style="color: #666666">1000</span>):
|
|
<span style="color: #408080; font-style: italic"># calculate gradients</span>
|
|
dWo, dBo, dWh, dBh <span style="color: #666666">=</span> backpropagation(X_train, Y_train_onehot)
|
|
|
|
<span style="color: #408080; font-style: italic"># regularization term gradients</span>
|
|
dWo <span style="color: #666666">+=</span> lmbd <span style="color: #666666">*</span> output_weights
|
|
dWh <span style="color: #666666">+=</span> lmbd <span style="color: #666666">*</span> hidden_weights
|
|
|
|
<span style="color: #408080; font-style: italic"># update weights and biases</span>
|
|
output_weights <span style="color: #666666">-=</span> eta <span style="color: #666666">*</span> dWo
|
|
output_bias <span style="color: #666666">-=</span> eta <span style="color: #666666">*</span> dBo
|
|
hidden_weights <span style="color: #666666">-=</span> eta <span style="color: #666666">*</span> dWh
|
|
hidden_bias <span style="color: #666666">-=</span> eta <span style="color: #666666">*</span> dBh
|
|
|
|
<span style="color: #008000; font-weight: bold">print</span>(<span style="color: #BA2121">"New accuracy on training data: "</span> <span style="color: #666666">+</span> <span style="color: #008000">str</span>(accuracy_score(predict(X_train), Y_train)))
|
|
</pre></div>
|
|
<p>
|
|
<p>
|
|
<!-- navigation buttons at the bottom of the page -->
|
|
<ul class="pagination">
|
|
<li><a href="._NeuralNet-bs043.html">«</a></li>
|
|
<li><a href="._NeuralNet-bs000.html">1</a></li>
|
|
<li><a href="">...</a></li>
|
|
<li><a href="._NeuralNet-bs036.html">37</a></li>
|
|
<li><a href="._NeuralNet-bs037.html">38</a></li>
|
|
<li><a href="._NeuralNet-bs038.html">39</a></li>
|
|
<li><a href="._NeuralNet-bs039.html">40</a></li>
|
|
<li><a href="._NeuralNet-bs040.html">41</a></li>
|
|
<li><a href="._NeuralNet-bs041.html">42</a></li>
|
|
<li><a href="._NeuralNet-bs042.html">43</a></li>
|
|
<li><a href="._NeuralNet-bs043.html">44</a></li>
|
|
<li class="active"><a href="._NeuralNet-bs044.html">45</a></li>
|
|
<li><a href="._NeuralNet-bs045.html">46</a></li>
|
|
<li><a href="._NeuralNet-bs046.html">47</a></li>
|
|
<li><a href="._NeuralNet-bs047.html">48</a></li>
|
|
<li><a href="._NeuralNet-bs048.html">49</a></li>
|
|
<li><a href="._NeuralNet-bs049.html">50</a></li>
|
|
<li><a href="._NeuralNet-bs050.html">51</a></li>
|
|
<li><a href="._NeuralNet-bs051.html">52</a></li>
|
|
<li><a href="._NeuralNet-bs052.html">53</a></li>
|
|
<li><a href="._NeuralNet-bs053.html">54</a></li>
|
|
<li><a href="">...</a></li>
|
|
<li><a href="._NeuralNet-bs057.html">58</a></li>
|
|
<li><a href="._NeuralNet-bs045.html">»</a></li>
|
|
</ul>
|
|
<!-- ------------------- end of main content --------------- -->
|
|
|
|
</div> <!-- end container -->
|
|
<!-- include javascript, jQuery *first* -->
|
|
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
|
|
<script src="https://netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
|
|
|
|
<!-- Bootstrap footer
|
|
<footer>
|
|
<a href="http://..."><img width="250" align=right src="http://..."></a>
|
|
</footer>
|
|
-->
|
|
|
|
|
|
<center style="font-size:80%">
|
|
<!-- copyright only on the titlepage -->
|
|
</center>
|
|
|
|
|
|
</body>
|
|
</html>
|
|
|
|
|