Faster Game Solving via Hyperparameter Schedules

The counterfactual regret minimization (CFR) family of algorithms consists of iterative algorithms for imperfect-information games. In two-player zero-sum games, the time average of the iterates converges to a Nash equilibrium. The state-of-the-art prior variants, Discounted CFR (DCFR) and Predictive CFR^+ (PCFR^+) are the fastest known algorithms for solving two-player zero-sum games in practice, both in the extensive-form setting and the normal-form setting. They enhance the convergence rate compared to vanilla CFR by applying discounted weights to early iterations in various ways, leveraging fixed weighting schemes. We introduce Hyperparameter Schedules (HSs), which are remarkably simple yet highly effective in expediting the rate of convergence. HS dynamically adjusts the hyperparameter governing the discounting scheme of CFR variants. HSs on top of DCFR or PCFR^+ is now the new state of the art in solving zero-sum games and yields orders-of-magnitude speed improvements. The new algorithms are also easy to implement because 1) they are small modifications to the existing ones in terms of code and 2) they require no game-specific tuning.