($10) Some calculations produce NaN

[micheljung]

This works fine:

  @Test
  public void testOk() {
    GameInfo gameInfo = new GameInfo(1500, 500, 240, 10, 0.1);
    Collection<ITeam> ts = Arrays.asList(
      new Team().addPlayer(new jskills.Player<>(1), new Rating(3453, 74)),
      new Team().addPlayer(new jskills.Player<>(2), new Rating(38, 181))
    );
    Map<IPlayer, Rating> newRatings = TrueSkillCalculator.calculateNewRatings(gameInfo, new ArrayList<>(ts), 1, 2);

    newRatings.forEach((iPlayer, rating) -> System.out.println(rating));
  }

Output:

Mean(μ)=3453.000000, Std-Dev(σ)=74.672619
Mean(μ)=38.000000, Std-Dev(σ)=181.276033

While this produces NaN (note that only player 2's deviation has been changed)

  @Test
  public void testNaN() {
    GameInfo gameInfo = new GameInfo(1500, 500, 240, 10, 0.1);
    Collection<ITeam> ts = Arrays.asList(
      new Team().addPlayer(new jskills.Player<>(1), new Rating(3453, 74)),
      new Team().addPlayer(new jskills.Player<>(2), new Rating(38, 180))
    );
    Map<IPlayer, Rating> newRatings = TrueSkillCalculator.calculateNewRatings(gameInfo, new ArrayList<>(ts), 1, 2);

    newRatings.forEach((iPlayer, rating) -> System.out.println(rating));
  }

Output:

Mean(μ)=NaN, Std-Dev(σ)=74.672619
Mean(μ)=38.000000, Std-Dev(σ)=180.277564

[micheljung]

Same Bug in Skills (moserware#12)

[pmg1991]

@micheljung Please review the code.

[nsp]

LGTM