README

Description

This project is a simple library that allows PHP developers to easily build their own applications by using Genetic Algorithms.

Installation

To install this library, you can use composer:

composer require sedatsevgili/charlie

Usage

To use this library for your own purposes as a PHP developer, you need to:

Define your own Gene class that will implement the Charlie\Gene\GeneInterface interface.
Define your own FitnessFunction class that will implement the Charlie\Fitness\CalculatorInterface interface.
Define your own Selection class that will implement the Charlie\Actions\Selection\SelectorInterface interface.
Build your populations by implementing the Charlie\Population\PopulationBuilderInterface interface.
Define your problem by using the Charlie\Problem\Problem class.
Run the solve method of the Charlie\Problem\Problem class.

Example

Let's say we want to find the best possible solution for the following knapsack problem:

We have a list of 10 items. Each item has a weight and a value. We want to find the best combination of items that will maximize the total value of the items, but the total weight of the items must not exceed 15.

First, we need to define our Gene class. In our example, a Gene will be an item from the list. Therefore, we need to create a class that will represent an item from the list. Let's call it Item. The Item class needs to implement the Charlie\Gene\GeneInterface interface. Here is how the Item class will look like:

<?php

class Item implements \Charlie\Gene\GeneInterface
{

    private bool $picked;

    public function __construct(private int $weight, private int $value)
    {
        $this->weight = $weight;
        $this->value = $value;
        $this->picked = false;
    }

    public function getWeight(): int
    {
        return $this->weight;
    }

    public function setWeight(int $weight): self
    {
        $this->weight = $weight;
        return $this;
    }

    public function getValue(): int
    {
        return $this->value;
    }

    public function setValue(int $value): self
    {
        $this->value = $value;
        return $this;
    }

    public function isPicked(): bool
    {
        return $this->picked;
    }

    public function set(mixed $data): \Charlie\Gene\GeneInterface
    {
        $this->setValue($data['value'] ?? 0);
        $this->setWeight($data['weight'] ?? 0);
        return $this;
    }

    public function get(): mixed
    {
        return [
            'value' => $this->getValue(),
            'weight' => $this->getWeight(),
        ];
    }

    public function mutate(): \Charlie\Gene\GeneInterface
    {
        $this->picked = !$this->picked;
        return $this;
    }

    public function __toString(): string
    {
        return sprintf('Value: %s, Weight: %s, Picked: %s', $this->getValue(), $this->getWeight(), $this->isPicked() ? 'Yes' : 'No');
    }

    public function isEqual(\Charlie\Gene\GeneInterface $gene): bool
    {
        return $this->getValue() === $gene->getValue() && $this->getWeight() === $gene->getWeight();
    }

}

Next, we need to define our FitnessFunction class. In our example, the FitnessFunction will calculate the total value of a combination of items. Therefore, we need to create a class that will calculate the total value of a combination of items. Let's call it KnapsackFitnessFunction. The KnapsackFitnessFunction class needs to implement the Charlie\Fitness\CalculatorInterface interface. Here is how the KnapsackFitnessFunction class will look like:

<?php

class KnapsackFitnessFunction implements \Charlie\Fitness\CalculatorInterface
{

    public function calculate(\Charlie\Chromosome\Chromosome $chromosome): int
    {
        $items = $chromosome->getData();
        $items = array_filter($items, function (Item $item) {
            return $item->isPicked();
        });
        $totalValue = array_reduce($items, function ($carry, $item) {
            return $carry + $item->getValue();
        }, 0);
        $totalWeight = array_reduce($items, function ($carry, $item) {
            return $carry + $item->getWeight();
        }, 0);
        if ($totalWeight > 15) {
            $totalValue = 0;
        }

        return $totalValue;
    }

}

Now, we can solve our problem. In our example, we will run the Problem class. Here is how we run it:

<?php
require_once __DIR__ . '/../../vendor/autoload.php';
require_once __DIR__ . '/KnapsackFitnessFunction.php';
require_once __DIR__ . '/Item.php';

$combination1 = [
    new Item(1, 1),
    new Item(2, 3),
    new Item(3, 5),
    new Item(4, 7),
    new Item(5, 9),
    new Item(6, 11),
    new Item(7, 13),
];
$combination2 = [
    new Item(1, 1),
    new Item(2, 3),
    new Item(3, 5),
    new Item(4, 7),
    new Item(4, 6),
    new Item(6, 11),
    new Item(7, 13),
];
$combination3 = [
    new Item(1, 1),
    new Item(2, 3),
    new Item(3, 5),
    new Item(4, 7),
    new Item(4, 7),
    new Item(6, 10),
    new Item(7, 13),
];
$combination4 = [
    new Item(1, 1),
    new Item(2, 3),
    new Item(4, 5),
    new Item(4, 7),
    new Item(5, 9),
    new Item(3, 1),
    new Item(7, 13),
];
$combination5 = [
    new Item(1, 1),
    new Item(2, 3),
    new Item(4, 5),
    new Item(6, 7),
    new Item(5, 9),
    new Item(3, 10),
    new Item(7, 13),
];

$population = new \Charlie\Population\Population([
    new \Charlie\Individual\Individual(new \Charlie\Chromosome\Chromosome($combination1)),
    new \Charlie\Individual\Individual(new \Charlie\Chromosome\Chromosome($combination2)),
    new \Charlie\Individual\Individual(new \Charlie\Chromosome\Chromosome($combination3)),
    new \Charlie\Individual\Individual(new \Charlie\Chromosome\Chromosome($combination4)),
    new \Charlie\Individual\Individual(new \Charlie\Chromosome\Chromosome($combination5)),
]);

$fitnessFunction = new KnapsackFitnessFunction();
$selection = new \Charlie\Actions\PairSelection();

$problem = new \Charlie\Actions\Problem\Problem();
$problem->setCalculator($fitnessFunction);
$problem->setCrossOver(new \Charlie\Actions\CrossOver(new \Charlie\Randomizer\MtRandomizer()));
$problem->setMutator(new \Charlie\Actions\Mutator(new \Charlie\Randomizer\MtRandomizer()));
$problem->setSelection($selection);
$problem->setMaxEvolveCount(100);
$problem->setPopulation($population);

$problem->solve();

echo "SOLUTION: " . PHP_EOL;
$bestParents = $selection->selectBest($population, $fitnessFunction);
echo (string) $bestParents->getIndividual1() . PHP_EOL;

License

This library is licensed under the MIT License - see the LICENSE.md file for details.

MIT License
===========

SPDX short identifier: MIT

Further resources on the MIT License
-----------------------------------

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 - [Wikipedia: MIT License](https://en.wikipedia.org/wiki/MIT_License)

sedatsevgili / charlie

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