a simple simulator of ELO

ELO_demo.pde

import java.util.*;

static int count = 0;

class Player implements Comparable<Player> {
  int id;
  float score;
  int win;
  int lose;
  Player() {
    id = count++;
    score = 1000;
    win = 0;
    lose = 0;
  }

  public int compareTo(final Player p) {
    return score<p.score?1:-1;
  }
}

Vector<Player> players;
int total = 100;
float h;
float maxw;
float ELO_K = 16;
int times = 0;
int range = 10;

void setup() {
  size(1024, 768);
  players = new Vector<Player>();
  for (int i=0; i<total;i++) {
    players.add(new Player());
  }
  h = (float)height / count;
  maxw = 1000;
  //  frameRate(1);
}

void draw() {
  //void mousePressed() {

  Collections.sort(players);
  redraw();
  //  for (int i=0;i<20;i++) {
  nearPlayersKill();
  //  }
  fill(0);
  textSize(32);
  text(times, width/2, height/2);
}

int r = 0;

void redraw() {
  background(200);
  for (int i=0;i<count;i++) {
    Player p = players.get(i);
    maxw = max(maxw, p.score);
    if (p.id==13) {
      r = i;
      fill(255, 255, 0);
    }
    else
      fill(255);
    rect(0, i*h, width*p.score/maxw, h);
    textSize(h);
    fill(128);
    text("id:"+p.id+"     "+(int)p.score+"     "+p.win+"    "+p.lose, 10, (i+1)*h);
  }
}

void randomPlayersKill() {
  int r1 = (int)random(count);
  int r2 = (int)(r1 + random(count-1))%count;
  Player a = players.get(r1);
  Player b = players.get(r2);
  float exp = getExpect(a, b);
  float result = exp<random(1)?0:1;
  updateScore(a, b, result);
  times++;
}

void nearPlayersKill() {
  int r1 = (int)random(count);
  //  int r1=r;
  //  float offset = random(count/10.0);
  float f1 = min(r1, range);
  float f2 = min(count-(r1+1), range);
  float f = f1+f2;
  float offset = random(f) - f1;
  offset += offset<0?0:1;
  //  println(f1+" "+f2+" "+(int)offset);
  int r2 = r1+(int)offset;
  fill(200);
  ellipse(width/2, (r1+0.5)*h, h/2, h/2);
  fill(100);
  ellipse(width/2, (r2+0.5)*h, h/2, h/2);
  Player a = players.get(r1);
  Player b = players.get(r2);
  float exp = getExpect(a, b);
  //  println((int)a.score+" "+(int)b.score+" "+(int)(exp*100));
  float result = exp<random(1)?0:1;
  if (result==0) {
    a.lose++;
    b.win++;
  }
  else {
    a.win++;
    b.lose++;
  }

  updateScore(a, b, result);
  times++;
}

//void mousePressed() {
//  randomPlayersKill();
//}

void updateScore(Player a, Player b, float result) {
  a.score = a.score + ELO_K * (result - getExpect(a, b));
  b.score = b.score + ELO_K * ((1-result) - getExpect(b, a));
}

float getExpect(Player a, Player b) {
  return 1.0 / (1.0 + pow(10, (b.score - a.score) / 400.0));
}