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1 | <?php |
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2 | |||
3 | declare(strict_types=1); |
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4 | |||
5 | namespace Phpml\Helper\Optimizer; |
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6 | |||
7 | use Closure; |
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8 | |||
9 | /** |
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10 | * Batch version of Gradient Descent to optimize the weights |
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11 | * of a classifier given samples, targets and the objective function to minimize |
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12 | */ |
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13 | class GD extends StochasticGD |
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14 | { |
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15 | /** |
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16 | * Number of samples given |
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17 | * |
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18 | * @var int|null |
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19 | */ |
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20 | protected $sampleCount; |
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21 | |||
22 | public function runOptimization(array $samples, array $targets, Closure $gradientCb): array |
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23 | { |
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24 | $this->samples = $samples; |
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25 | $this->targets = $targets; |
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26 | $this->gradientCb = $gradientCb; |
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27 | $this->sampleCount = count($this->samples); |
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28 | |||
29 | // Batch learning is executed: |
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30 | $currIter = 0; |
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31 | $this->costValues = []; |
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32 | while ($this->maxIterations > $currIter++) { |
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33 | $theta = $this->theta; |
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34 | |||
35 | // Calculate update terms for each sample |
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36 | [$errors, $updates, $totalPenalty] = $this->gradient($theta); |
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0 ignored issues
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The variable
$totalPenalty does not exist. Did you forget to declare it?
This check marks access to variables or properties that have not been declared yet. While PHP has no explicit notion of declaring a variable, accessing it before a value is assigned to it is most likely a bug.
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37 | |||
38 | $this->updateWeightsWithUpdates($updates, $totalPenalty); |
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39 | |||
40 | $this->costValues[] = array_sum($errors) / $this->sampleCount; |
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41 | |||
42 | if ($this->earlyStop($theta)) { |
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43 | break; |
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44 | } |
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45 | } |
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46 | |||
47 | $this->clear(); |
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48 | |||
49 | return $this->theta; |
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50 | } |
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51 | |||
52 | /** |
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53 | * Calculates gradient, cost function and penalty term for each sample |
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54 | * then returns them as an array of values |
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55 | */ |
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56 | protected function gradient(array $theta): array |
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57 | { |
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58 | $costs = []; |
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59 | $gradient = []; |
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60 | $totalPenalty = 0; |
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61 | |||
62 | foreach ($this->samples as $index => $sample) { |
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63 | $target = $this->targets[$index]; |
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64 | |||
65 | $result = ($this->gradientCb)($theta, $sample, $target); |
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66 | [$cost, $grad, $penalty] = array_pad($result, 3, 0); |
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0 ignored issues
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The variable
$penalty does not exist. Did you mean $totalPenalty ?
This check looks for variables that are accessed but have not been defined. It raises an issue if it finds another variable that has a similar name. The variable may have been renamed without also renaming all references.
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67 | |||
68 | $costs[] = $cost; |
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69 | $gradient[] = $grad; |
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70 | $totalPenalty += $penalty; |
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71 | } |
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72 | |||
73 | $totalPenalty /= $this->sampleCount; |
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74 | |||
75 | return [$costs, $gradient, $totalPenalty]; |
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76 | } |
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77 | |||
78 | protected function updateWeightsWithUpdates(array $updates, float $penalty): void |
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79 | { |
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80 | // Updates all weights at once |
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81 | for ($i = 0; $i <= $this->dimensions; ++$i) { |
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82 | if ($i === 0) { |
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83 | $this->theta[0] -= $this->learningRate * array_sum($updates); |
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84 | } else { |
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85 | $col = array_column($this->samples, $i - 1); |
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86 | |||
87 | $error = 0; |
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88 | foreach ($col as $index => $val) { |
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89 | $error += $val * $updates[$index]; |
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90 | } |
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91 | |||
92 | $this->theta[$i] -= $this->learningRate * |
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93 | ($error + $penalty * $this->theta[$i]); |
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94 | } |
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95 | } |
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96 | } |
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97 | |||
98 | /** |
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99 | * Clears the optimizer internal vars after the optimization process. |
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100 | */ |
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101 | protected function clear(): void |
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102 | { |
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103 | $this->sampleCount = null; |
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104 | parent::clear(); |
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105 | } |
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106 | } |
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107 |
This check marks access to variables or properties that have not been declared yet. While PHP has no explicit notion of declaring a variable, accessing it before a value is assigned to it is most likely a bug.