Merge pull request #57 from dexonsmith/cap-expected-win-rate-to-1-in-…

…a-million

When tallying, cap the expected win rate at 1:1M

analysis/util/TallyGameAnalytics.py

@@ -99,7 +99,9 @@ def add_glicko2_analytics(self, result: Glicko2Analytics) -> None:
                                 if result.expected_win_rate > 0.5
                                 else (not black_won if result.expected_win_rate < 0.5 else 0.5)
                             )
-                            self.prediction_cost[size][speed][rank][handicap] += - math.log(result.expected_win_rate if black_won else 1 - result.expected_win_rate)
+                            # Cap the expected win rate at 1 in 1M to avoid MathDomain errors.
+                            capped_win_rate = max(min(result.expected_win_rate, 0.999999), 0.000001)
+                            self.prediction_cost[size][speed][rank][handicap] += - math.log(capped_win_rate if black_won else 1 - capped_win_rate)
                             self.count[size][speed][rank][handicap] += 1
 
     def add_gor_analytics(self, result: GorAnalytics) -> None: