def performance_ratings(max, thresh)
      stable, count = false, 0
      while !stable && count < max
        @player.values.each { |p| p.estimate_performance }
        stable = @player.values.inject(true) { |ok, p| p.update_performance(thresh) && ok }
        count+= 1
      end
      raise "performance rating estimation did not converge" if max > 1 && !stable
      count
    end
def performance_ratings(max, thresh)
      stable, count = false, 0
      while !stable && count < max
        @player.values.each { |p| p.estimate_performance }
        stable = @player.values.inject(true) { |ok, p| p.update_performance(thresh) && ok }
        count+= 1
      end
      raise "performance rating estimation did not converge" if max > 1 && !stable
      count
    end
Create a new, empty (no players, no results) tournament.
 Calculate performance ratings either iteratively up to a maximum number.