package fr.uge.concurrence;

public class RandomNumberGenerator {
  private long x;
  
  public RandomNumberGenerator(long seed) {
    if (seed == 0) {
      throw new IllegalArgumentException("seed == 0");
    }
    x = seed;
  }
  
  public long next() {  // Marsaglia's XorShift
    x ^= x >>> 12;
    x ^= x << 25;
    x ^= x >>> 27;
    return x * 2685821657736338717L;
  }
  
  public static void main(String[] args) {
    var set0 = new HashSet<Long>();
    var set1 = new HashSet<Long>();
    var set2 = new HashSet<Long>();
    var rng0 = new RandomNumberGenerator(1);
    var rng = new RandomNumberGenerator(1);

    for (var i = 0; i < 10_000; i++) {
      set0.add(rng0.next());
    }

    var t = new Thread(() -> {
      for (var i = 0; i < 5_000; i++) {
        set1.add(rng.next());
      }
    });
    t.start();
    for (var i = 0; i < 5_000; i++) {
      set2.add(rng.next());
    }
    t.join();

    System.out.println("set1: " + set1.size() + ", set2: " + set2.size());

    set1.addAll(set2);
    System.out.println("union (should be 10 000): " + set1.size());

    System.out.println("intersection (should be true): " + set0.containsAll(set1));

    set0.removeAll(set1);
    System.out.println("intersection (should be 0): " + set0.size());
  }
}