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<?php |
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declare(strict_types=1); |
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namespace lucidtaz\minimax\engine; |
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use BadMethodCallException; |
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use LogicException; |
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use lucidtaz\minimax\game\GameState; |
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use lucidtaz\minimax\game\Player; |
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use RuntimeException; |
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/** |
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* MiniMax game engine |
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* |
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* Construct an object of this class, give it the player to optimize for, and |
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* call decide() when it is time for the player to make a move, in order to get |
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* the Decision that the engine has taken for the player. |
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*/ |
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class Engine |
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{ |
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private $objectivePlayer; |
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private $maxDepth; |
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/** |
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* @var Analytics|null Only available after run, contains statistics about the |
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* execution. |
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*/ |
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private $analytics; |
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/** |
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* @param Player $objectivePlayer The player to play as. The engine will try |
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* to maximize this player's score. |
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* @param int $maxDepth How many turns ahead should the engine look? |
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*/ |
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public function __construct(Player $objectivePlayer, int $maxDepth = 3) |
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{ |
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$this->objectivePlayer = $objectivePlayer; |
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$this->maxDepth = $maxDepth; |
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} |
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/** |
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* Evaluate possible decisions and take the best one |
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* |
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* @param GameState $state Current state of the game for which there needs |
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* to be made a decision. This implicitly means that the objective player |
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* currently must have its turn in the GameState. |
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* @return GameState The state resulting after the engine made its decision. |
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*/ |
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public function decide(GameState $state): GameState |
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{ |
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if (!$state->getNextPlayer()->equals($this->objectivePlayer)) { |
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throw new BadMethodCallException('It is not this players turn'); |
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} |
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if (empty($state->getPossibleMoves())) { |
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throw new RuntimeException('There are no possible moves'); |
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} |
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$rootNode = new DecisionNode( |
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$this->objectivePlayer, |
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$state, |
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$this->maxDepth, |
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NodeType::MAX(), |
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AlphaBeta::initial() |
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); |
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$moveWithEvaluation = $rootNode->traverseGameTree(); |
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$this->analytics = $moveWithEvaluation->analytics; |
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if ($moveWithEvaluation->move === null) { |
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throw new LogicException('Could not find move even though there are moves. Is the maxDepth parameter correct?'); |
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} |
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return $moveWithEvaluation->move; |
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} |
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public function getAnalytics(): Analytics |
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{ |
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if ($this->analytics === null) { |
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throw new BadMethodCallException('Please run decide() first.'); |
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} |
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return $this->analytics; |
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} |
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} |
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LucidTaZ /
minimax
