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minimax.js
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minimax.js
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class Minimax {
constructor(board) {
this.maxDepth = 3;
this.maxPermutations = 5000000;
this.permutations = 0;
this.evaluation = 0;
this.movesPlayed = 0;
this.maximizingTeam = 0;
this.winSide = 1;
this.tree = new Tree();
}
playMove(board, move) {
this.movesPlayed++;
move.to.ball = move.from.ball;
move.to.ball.hole = move.to;
move.from.ball = null;
}
unplayMove(board, move) {
this.movesPlayed--;
move.from.ball = move.to.ball;
move.from.ball.hole = move.from;
move.to.ball = null;
}
getBallScore(board, ball) {
const SIGNED_SIDE = (ball.team * 2 - 1);
let score = 0;
// Target point for each team
let target = null;
switch (ball.team) {
case 0: target = [16, 0]; break;
case 1: target = [0, 0]; break;
}
let targetHole = board.cols[target[0]][target[1]];
// Calculate distance to target
// let d = dist(
// ball.hole.px, ball.hole.py,
// targetHole.px, targetHole.py
// );
let d = Math.abs(targetHole.px - ball.hole.px);
d += Math.abs(targetHole.py - ball.hole.py) / 2;
// Set score relative to distance
score = 16 - d;
// Count neighbors
let teamates = 0;
for (let neighbor of ball.hole.neighbors) {
if (neighbor == null) continue;
const hole = board.cols[neighbor.c][neighbor.r];
if (hole.ball == null) continue;
if (hole.ball.team == ball.team) teamates++;
score += 0.1;
}
const WEIGHT = 0.75;
// if (this.maximizingTeam == 0)
if (teamates == 0) {
score -= d * WEIGHT;
}
return {
score: score * SIGNED_SIDE,
dist: d
};
}
getBoardScore(board, prnt = false) {
let totalScore = 0;
// Get score of all balls
for (let i=0; i<board.teamBalls.length; i++) {
const totalBalls = 10;
const SIGNED_SIDE = (i * 2 - 1); // only works with 2 teams
let distScore = 0;
let totalDist = 0;
let dists = [];
// Get score of each ball
for (let ball of board.teamBalls[i]) {
let data = this.getBallScore(board, ball);
totalScore += data.score;
totalDist += data.dist;
dists.push(data.dist);
}
// Calculate dist score
// const avgDist = totalDist / totalBalls;
// const WEIGHT = 0.75;
// let stragglers = 0;
// if (prnt) print("average dist: ", avgDist);
// for (let d of dists) {
// Scores greater than average receive higher scores
// Vise - versa
// Test for outliers
// if (d - avgDist > 4) {
// distScore += d - avgDist;
// stragglers++;
// }
// }
// if (prnt) print(round(distScore * SIGNED_SIDE * 100) / 100);
// totalScore += (distScore * SIGNED_SIDE * WEIGHT) / (1 + stragglers);
}
return round(totalScore * 1000) / 1000;
}
getPossibleMoves(board, turn) {
let balls = board.teamBalls[turn];
let allMoves = [];
// Looks good (gather possible moves)
for (let ball of balls) {
let moves = board.control.getMoves(ball.hole);
board.control.clearVisited();
// let score0 = this.getBallScore(board, ball);
for (let move of moves) {
// move.ball = ball;
// let score1 = this.getBallScore(board, move.ball);
// move.ball = null;
allMoves.push({from:ball.hole, to:move, /*scoreDiff: score1 - score0*/});
}
}
/*allMoves.sort(function(a, b) {
return b.scoreDiff - a.scoreDiff;
});*/
return allMoves;
}
getWinState(board) {
// Might not be worth calculating this
// +1 (white wins)
// -1 (black wins)
// 0 (draw)
// null (continue)
// win score: 141.784 points
// All balls on winning side
// Black win
let blackExists = false;
let full = true;
for (let i=13; i<17; i++) {
for (let hole of board.cols[i]) {
if (!hole.ball) {
full = false;
break;
} else {
if (hole.ball.team == 0) blackExists = true;
}
}
}
if (full && blackExists) return -1;
// White win (all full and at least one white)
let whiteExists = false;
full = true;
for (let i=0; i<4; i++) {
for (let hole of board.cols[i]) {
if (!hole.ball) {
full = false;
break;
} else {
if (hole.ball.team == 1) whiteExists = true;
}
}
}
if (full && whiteExists) return 1;
// let win = true;
// for (let ball of board.teamBalls[0]) {
// if (ball.hole.c < 13) {
// win = false;
// break;
// }
// }
// if (win) return -1;
// win = true;
// for (let ball of board.teamBalls[1]) {
// if (ball.hole.c > 3) {
// win = false;
// break;
// }
// }
// if (win) return 1;
return null;
}
minimax(board, turn, depth, alpha, beta) {
this.permutations++;
let winner = this.getWinState(board); // [win, winner, points]
let maximizing = turn == this.maximizingTeam;
// Winner
if (winner != null) {
// positive : same team
// negative : opposite team
return [winner * (10000 - this.movesPlayed) * this.winSide];
}
// Max depth / permutations reached
if (depth >= this.maxDepth || this.permutations > this.maxPermutations) {
return [this.getBoardScore(board) * this.winSide];
}
let moves = this.getPossibleMoves(board, turn);
// Next turn
turn = (turn + 1) % board.teams;
if (maximizing) {
let maxEval = -Infinity, maxAlpha = false;
let bestMove;
// Further analysis
for (let i=0; i<moves.length; i++) {
let move = moves[i];
// Play move
this.playMove(board, move);
// Calculate next position
let result = this.minimax(board, turn, depth + 1, alpha, beta);
let score = result[0];
// Unplay move
this.unplayMove(board, move);
// Calculate score
if (score > maxEval) {
maxEval = score;
bestMove = move;
}
maxEval = max(maxEval, score);
alpha = max(alpha, score);
if (beta <= alpha) break;
// if (score > maxEval) {
// maxEval = score;
// bestMove = move;
// if (maxAlpha || score > alpha) {
// alpha = score;
// maxAlpha = true;
// if (beta <= alpha) {
// print("pruned!");
// break;
// }
// }
// }
}
// Return score
return [maxEval, bestMove];
} else {
let minEval = Infinity, minBeta = false;
let bestMove;
for (let i=0; i<moves.length; i++) {
let move = moves[i];
// Play move
this.playMove(board, move);
// Calculate next position
let result = this.minimax(board, turn, depth + 1, alpha, beta);
let score = result[0];
// Unplay move
this.unplayMove(board, move);
// Calculate score
if (score < minEval) {
minEval = score;
bestMove = move;
}
minEval = min(minEval, score);
beta = min(beta, score);
if (beta <= alpha) break;
// if (score < minEval) {
// minEval = score;
// bestMove = move;
// if (minBeta || score > beta) {
// beta = score;
// minBeta = true;
// if (beta <= alpha) break;
// }
// }
}
// Return score
return [minEval, bestMove];
}
}
bestMove(board) {
let turn = board.control.turn;
let topMove = {score:-Infinity};
this.permutations = 0;
this.maximizingTeam = turn;
this.winSide = (turn * 2 - 1);
let result = this.minimax(board, turn, 0, -Infinity, Infinity);
game.board.control.playMove(result[1]);
this.evaluation = result[0];
// this.playMove(board, result[1]);
// board.control.turn = (turn + 1) % board.teams;
}
}
class Tree {
constructor(parent = null, move = null, moves = null) {
this.branches = [];
this.parent = parent;
this.currentBranch = this;
this.move = move;
this.moves = moves;
this.score = null;
}
createBranch(move, moves) {
this.currentBranch.branches.push(new Tree(this, move, moves));
}
seekBranch(i, move, moves) {
if (i >= this.currentBranch.branches.length)
this.createBranch(move, moves);
// Go down the tree
this.currentBranch = this.currentBranch.branches[i];
}
bubble() {
// Go up the tree
this.currentBranch = this.currentBranch.parent;
}
setStats(score) {
this.currentBranch.score = score;
}
}
/*
/* OLD:
// Horizontal travel distance
if (ball.team == 0) {
score = ball.hole.c;
// Past column 12
// if (ball.hole.c > 12) score = 10;
// else score = ball.hole.c / 12 * 6;
} else {
score = 16 - ball.hole.c;
}
*/