27 lines
761 B
Python
27 lines
761 B
Python
"""ELO rating calculation."""
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def calculate_elo(
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winner_rating: float,
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loser_rating: float,
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k_factor: float = 32.0,
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) -> tuple[float, float]:
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"""Calculate new ELO ratings after a match.
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Uses the standard ELO formula:
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E = 1 / (1 + 10^((R_opponent - R_self) / 400))
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R_new = R_old + K * (S - E)
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where S = 1 for a win, S = 0 for a loss.
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Returns:
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(new_winner_rating, new_loser_rating)
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"""
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expected_winner = 1.0 / (1.0 + 10.0 ** ((loser_rating - winner_rating) / 400.0))
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expected_loser = 1.0 - expected_winner
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new_winner = winner_rating + k_factor * (1.0 - expected_winner)
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new_loser = loser_rating + k_factor * (0.0 - expected_loser)
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return round(new_winner, 2), round(new_loser, 2)
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