CLR Simulation (Interesting results...)

clr.js

var _ = require('lodash');
var chiSquaredTest = require('chi-squared-test');
var seedrandom = require('seedrandom');
var rng = seedrandom('hello.');

function rollDie(sides) {
  var index = Math.floor(rng() * sides.length);
  return sides[index];
}

function doTurn(seats, roller) {
  var leftNeighbor = (roller + seats.length - 1) % seats.length;
  var rightNeighbor = (roller + 1) % seats.length;

  // Roll only as many dice as the player has tokens
  var diceToRoll = Math.min(3, seats[roller]);
  _.range(diceToRoll).forEach(function() {
    var die = ['.', '.', '.', 'C', 'L', 'R'];
    var diceRollResult = rollDie(die);

    // If they got a dot, they're safe
    if(diceRollResult == '.') {
      return;
    }

    // otherwise, they'll lose a token
    seats[roller] -= 1;

    // L and R move the money left to right. C just makes the money go away...
    if(diceRollResult == 'L') {
      seats[leftNeighbor] += 1;
    } else if(diceRollResult == 'R') {
      seats[rightNeighbor] += 1;
    }
  });
}

function getWinner(seats) {
  // map the seats to a list of players with index and number of "tokens" left
  var remainingPlayers = seats.map(function(seat, index) {
    return {
      tokens: seat,
      index: index
    };
  }).filter(function(seat) {
    return seat.tokens > 0;
  });

  if(remainingPlayers.length == 1) {
    return remainingPlayers[0].index;
  }
}

function doTest(N) {
  // initialize the seats
  var seats = _.range(N).map(function() { return 3; });
  var currentPlayer = 0;
  while(getWinner(seats) === undefined) {
    doTurn(seats, currentPlayer);
    currentPlayer = (currentPlayer + 1) % N;
  }

  return getWinner(seats);
}

var N = 5;
var bins = _.range(N).map(function() { return 0; });

var sampleCount = 100000;
_.range(sampleCount).forEach(function() {
  var winner = doTest(N);
  bins[winner] += 1;
});

console.log(bins);

// Chi-squared test it! We expect uniform distribution
var expected = _.range(N).map(function() {
  return sampleCount / N;
});

var reduction = 1;

var probability = chiSquaredTest(bins, expected, reduction);
console.log('Probability of uniform?', probability);

package.json

{
  "name": "JUNK",
  "version": "1.0.0",
  "description": "",
  "main": "clr.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "chi-squared-test": "^1.1.0",
    "lodash": "^4.0.0",
    "seedrandom": "^2.4.2"
  }
}