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1 | <?php |
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2 | |||
3 | declare(strict_types=1); |
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4 | |||
5 | namespace Phpml\NeuralNetwork\Training; |
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6 | |||
7 | use Phpml\NeuralNetwork\Node\Neuron; |
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8 | use Phpml\NeuralNetwork\Training\Backpropagation\Sigma; |
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9 | |||
10 | class Backpropagation |
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11 | { |
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12 | /** |
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13 | * @var float |
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14 | */ |
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15 | private $learningRate; |
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16 | |||
17 | /** |
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18 | * @var array |
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19 | */ |
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20 | private $sigmas = null; |
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21 | |||
22 | /** |
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23 | * @var array |
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24 | */ |
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25 | private $prevSigmas = null; |
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26 | |||
27 | public function __construct(float $learningRate) |
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28 | { |
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29 | $this->setLearningRate($learningRate); |
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30 | } |
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31 | |||
32 | public function setLearningRate(float $learningRate): void |
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33 | { |
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34 | $this->learningRate = $learningRate; |
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35 | } |
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36 | |||
37 | /** |
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38 | * @param mixed $targetClass |
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39 | */ |
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40 | public function backpropagate(array $layers, $targetClass): void |
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41 | { |
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42 | $layersNumber = count($layers); |
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43 | |||
44 | // Backpropagation. |
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45 | for ($i = $layersNumber; $i > 1; --$i) { |
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46 | $this->sigmas = []; |
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47 | foreach ($layers[$i - 1]->getNodes() as $key => $neuron) { |
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48 | if ($neuron instanceof Neuron) { |
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49 | $sigma = $this->getSigma($neuron, $targetClass, $key, $i == $layersNumber); |
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50 | foreach ($neuron->getSynapses() as $synapse) { |
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51 | $synapse->changeWeight($this->learningRate * $sigma * $synapse->getNode()->getOutput()); |
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52 | } |
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53 | } |
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54 | } |
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55 | |||
56 | $this->prevSigmas = $this->sigmas; |
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57 | } |
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58 | |||
59 | // Clean some memory (also it helps make MLP persistency & children more maintainable). |
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60 | $this->sigmas = null; |
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61 | $this->prevSigmas = null; |
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62 | } |
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63 | |||
64 | private function getSigma(Neuron $neuron, int $targetClass, int $key, bool $lastLayer): float |
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65 | { |
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66 | $neuronOutput = $neuron->getOutput(); |
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67 | $sigma = $neuronOutput * (1 - $neuronOutput); |
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68 | |||
69 | if ($lastLayer) { |
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70 | $value = 0; |
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71 | if ($targetClass === $key) { |
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72 | $value = 1; |
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73 | } |
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74 | |||
75 | $sigma *= ($value - $neuronOutput); |
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76 | } else { |
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77 | $sigma *= $this->getPrevSigma($neuron); |
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78 | } |
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79 | |||
80 | $this->sigmas[] = new Sigma($neuron, $sigma); |
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81 | |||
82 | return $sigma; |
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83 | } |
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84 | |||
85 | private function getPrevSigma(Neuron $neuron): float |
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86 | { |
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87 | $sigma = 0.0; |
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88 | |||
89 | foreach ($this->prevSigmas as $neuronSigma) { |
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90 | $sigma += $neuronSigma->getSigmaForNeuron($neuron); |
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91 | } |
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92 | |||
93 | return $sigma; |
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94 | } |
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95 | } |
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96 |
Our type inference engine has found an assignment to a property that is incompatible with the declared type of that property.
Either this assignment is in error or the assigned type should be added to the documentation/type hint for that property..