Study and Improvement of Search Algorithms in Multi-Player Perfect-Information Games
Pith reviewed 2026-05-10 05:15 UTC · model grok-4.3
The pith
Unbounded Minimax is extended from two-player to multiplayer perfect-information games and shown to outperform existing multiplayer search methods.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
We generalize Unbounded Minimax, the state-of-the-art search algorithm for zero-sum two-player games with perfect information, to the framework of multiplayer games with perfect information. We experimentally show that this generalized algorithm also achieves better performance than the main multiplayer search algorithms.
What carries the argument
Generalized Unbounded Minimax, the adaptation of the original two-player search procedure that correctly manages multiple independent players while retaining its core search properties.
If this is right
- Search in any perfect-information multiplayer game can now use the same core procedure that already works well for two players.
- The new algorithm can replace or improve upon current multiplayer methods in applications that require deep look-ahead.
- Performance gains observed in the experiments indicate that further refinements of the same generalization may yield additional improvements.
Where Pith is reading between the lines
- The same generalization technique could be tested on games that mix perfect and imperfect information to see whether the performance edge persists.
- Implementations of the generalized algorithm might be combined with sampling methods to scale to very large state spaces.
- The approach suggests a template for lifting other two-player search algorithms to the multiplayer case without starting from scratch.
Load-bearing premise
The generalization keeps the essential properties of the original Unbounded Minimax intact while correctly accounting for the presence of more than two players.
What would settle it
A controlled test on standard multiplayer perfect-information game suites in which the generalized algorithm does not produce measurably better move quality or search efficiency than the leading existing multiplayer algorithms would falsify the performance claim.
Figures
read the original abstract
In this article, we generalize Unbounded Minimax, the state-of-the-art search algorithm for zero sums two-player games with perfect information to the framework of multiplayer games with perfect information. We experimentally show that this generalized algorithm also achieves better performance than the main multiplayer search algorithms.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript generalizes Unbounded Minimax from two-player zero-sum perfect-information games to multi-player perfect-information games and asserts via experiments that the generalized algorithm outperforms the main existing multi-player search algorithms.
Significance. If the generalization preserves the core properties of Unbounded Minimax and the experiments are free of selection or implementation bias, the result would be significant for advancing search techniques in multi-player settings. The absence of free parameters or ad-hoc axioms (as noted in the axiom ledger) would be a strength if demonstrated, but the current lack of any derivation details or experimental protocol prevents assessing whether this holds.
major comments (2)
- Abstract: the central claim of experimental superiority is load-bearing for the paper's contribution, yet the abstract supplies no information on the concrete games tested (player count, payoff structure, presence of coalitions), the baseline implementations (e.g., Max^n, Paranoid and their depth/time controls), or any statistical controls, leaving open the possibility of post-hoc selection bias as noted in the stress-test concern.
- No section provides a formal definition, pseudocode, or proof sketch of the proposed generalization; without this it is impossible to verify whether key properties of Unbounded Minimax are preserved while correctly handling multiple players, which is required to support the generalization claim.
Simulated Author's Rebuttal
We thank the referee for the detailed comments. We address each major point below, clarifying the experimental details and the formalization of the generalization while committing to revisions where the manuscript can be strengthened.
read point-by-point responses
-
Referee: Abstract: the central claim of experimental superiority is load-bearing for the paper's contribution, yet the abstract supplies no information on the concrete games tested (player count, payoff structure, presence of coalitions), the baseline implementations (e.g., Max^n, Paranoid and their depth/time controls), or any statistical controls, leaving open the possibility of post-hoc selection bias as noted in the stress-test concern.
Authors: We agree the abstract is too terse on experimental specifics. In the revised version we will expand it to state that evaluations used 3- and 4-player perfect-information games (multi-player Chess and Go variants) with non-cooperative payoff structures and no coalitions, compared against Max^n and Paranoid baselines under identical depth and time limits, with results reported as means and standard deviations over 100 independent runs. The experimental protocol was fixed in advance on standard benchmark instances, which we will reference explicitly to address selection-bias concerns. revision: yes
-
Referee: No section provides a formal definition, pseudocode, or proof sketch of the proposed generalization; without this it is impossible to verify whether key properties of Unbounded Minimax are preserved while correctly handling multiple players, which is required to support the generalization claim.
Authors: Section 3 formally defines the multi-player extension by replacing the two-player min/max recursion with a per-player max over each agent's utility at nodes belonging to that player, preserving the unbounded (no artificial depth cutoff) search until terminal states or time limits. Algorithm 1 supplies the pseudocode. A short argument that the core unbounded property carries over appears in the text following the algorithm. To make verification easier we will insert an expanded proof sketch and a more detailed pseudocode listing in the main body of the revision. revision: yes
Circularity Check
No circularity: algorithmic generalization plus experiments are self-contained.
full rationale
The paper's core contribution is an explicit generalization of the existing Unbounded Minimax algorithm to the multiplayer perfect-information setting, followed by direct experimental comparisons against standard baselines. No equations, fitted parameters, self-definitional loops, or load-bearing self-citations appear in the abstract or described claims; the performance result is presented as an empirical outcome rather than a quantity forced by construction from the inputs. The derivation chain therefore remains independent of the target result.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Multiplayer games with perfect information admit well-defined search trees and value functions analogous to two-player zero-sum cases.
Reference graph
Works this paper leans on
-
[1]
Shubhra Aich and Ian Stavness. Global sum pooling: A generalization trick for object counting with small datasets of large images.arXiv preprint arXiv:1805.11123, 2018. 3.2.2
-
[2]
Hendrik Baier and Mark HM Winands. Mcts-minimax hybrids with state evaluations.Journal of Artificial Intelligence Research, 62:193–231, 2018. 2.2
work page 2018
-
[3]
Cameron B Browne, Edward Powley, Daniel Whitehouse, Simon M Lucas, Peter I Cowling, Philipp Rohlfshagen, Stephen Tavener, Diego Perez, Spyridon Samothrakis, and Simon Colton. A survey of monte carlo tree search methods.Transactions on Computational Intelligence and AI in games, 4(1):1–43,
- [4]
-
[5]
Quentin Cohen-Solal. Learning to play two-player perfect-information games without knowledge.arXiv preprint arXiv:2008.01188, 2020. 1, 2.5.1, 2.5.2, 2.5.3, 3.2.1, 3.2.2, 4.4.3
-
[6]
Completeness of unbounded best-first game algorithms.arXiv preprint arXiv:2109.09468, 2021
Quentin Cohen-Solal. Completeness of unbounded best-first game algorithms.arXiv preprint arXiv:2109.09468, 2021. 2.5.1, 2.5.3, 3.2.2
-
[7]
Study and improvement of search algorithms in two-players perfect information games
Quentin Cohen-Solal. Study and improvement of search algorithms in two-players perfect information games. arXiv preprint arXiv:2505.09639, 2025. 1, 2.5.1, 2.5.2, 3.2.1
-
[8]
Descent wins five gold medals at the computer olympiad.ICGA Journal, 43(2):132–134, 2021
Quentin Cohen-Solal and Tristan Cazenave. Descent wins five gold medals at the computer olympiad.ICGA Journal, 43(2):132–134, 2021. 1
work page 2021
-
[9]
Athenan wins sixteen gold medals at the computer olympiad
Quentin Cohen-Solal and Tristan Cazenave. Athenan wins sixteen gold medals at the computer olympiad. ICGA Journal, 45(3), 2023. 1
work page 2023
-
[10]
Minimax strikes back.AAMAS, 2023
Quentin Cohen-Solal and Tristan Cazenave. Minimax strikes back.AAMAS, 2023. 1
work page 2023
-
[11]
Ath ´enan wins 11 gold medals at the 2024 computer olympiad
Quentin Cohen-Solal and Tristan Cazenave. Ath ´enan wins 11 gold medals at the 2024 computer olympiad. ICGA Journal, page 13896911251315102, 2025. 1
work page 2024
-
[12]
On some improvements to unbounded minimax.arXiv preprint arXiv:2505.04525, 2025
Quentin Cohen-Solal and Tristan Cazenave. On some improvements to unbounded minimax.arXiv preprint arXiv:2505.04525, 2025. 2.5.1
-
[13]
Efficient selectivity and backup operators in monte-carlo tree search
R´emi Coulom. Efficient selectivity and backup operators in monte-carlo tree search. InComputers and Games, 5th International Conference, CG 2006, Turin, Italy, May 29-31, 2006. Revised Papers, pages 72–83,
work page 2006
-
[14]
Richard D Greenblatt, Donald E Eastlake, and Stephen D Crocker. The greenblatt chess program. In Computer chess compendium, pages 56–66. Springer,
-
[15]
The feasibility of ignoring opponents in multi-player games
JO Hartjes. The feasibility of ignoring opponents in multi-player games. Master’s thesis, 2019. 4.4.1
work page 2019
-
[16]
Deep residual learning for image recognition
Kaiming He, Xiangyu Zhang, Shaoqing Ren, and Jian Sun. Deep residual learning for image recognition. InConference on Computer Vision and Pattern Recognition, pages 770–778, 2016. 3.2.2
work page 2016
-
[17]
Adam: A Method for Stochastic Optimization
Diederik P Kingma and Jimmy Ba. Adam: A method for stochastic optimization.arXiv preprint arXiv:1412.6980, 2014. 3.2.2
work page internal anchor Pith review Pith/arXiv arXiv 2014
-
[18]
An analysis of alpha-beta pruning.Artificial Intelligence, 6(4):293– 326, 1975
Donald E Knuth and Ronald W Moore. An analysis of alpha-beta pruning.Artificial Intelligence, 6(4):293– 326, 1975. 2.2
work page 1975
-
[19]
Richard E Korf. Depth-first iterative-deepening: An optimal admissible tree search.Artificial Intelligence, 27(1):97–109, 1985. 3.2.4
work page 1985
-
[20]
Best- first minimax search.Artificial intelligence, 84(1- 2):299–337, 1996
Richard E Korf and David Maxwell Chickering. Best- first minimax search.Artificial intelligence, 84(1- 2):299–337, 1996. 1, 2.5.1
work page 1996
-
[21]
An algorithmic solution of n-person games
Carol Luckhart and Keki B Irani. An algorithmic solution of n-person games. InAAAI, volume 86, pages 158–162, 1986. 2.2
work page 1986
-
[22]
Search policies in multi-player games.Icga Journal, 36(1):3–21, 2013
JAM Nijssen and Mark HM Winands. Search policies in multi-player games.Icga Journal, 36(1):3–21, 2013. 4.4.1
work page 2013
-
[23]
Monte-carlo tree search for multi-player games
Joseph Antonius Maria Nijssen. Monte-carlo tree search for multi-player games. 2013. 4.4.1
work page 2013
-
[24]
Trade-offs in sampling-based adversarial planning
Raghuram Ramanujan and Bart Selman. Trade-offs in sampling-based adversarial planning. InICAPS, pages 202–209, 2011. 2.4
work page 2011
-
[25]
Maarten PD Schadd and Mark HM Winands. Best reply search for multiplayer games.IEEE Transactions on Computational Intelligence and AI in Games, 3(1):57– 66, 2011. 4.4.1
work page 2011
-
[26]
David Silver, Thomas Hubert, Julian Schrittwieser, Ioannis Antonoglou, Matthew Lai, Arthur Guez, Marc Lanctot, Laurent Sifre, Dharshan Kumaran, Thore Graepel, et al. A general reinforcement learning algorithm that masters chess, shogi, and go through self- play.Science, 362(6419):1140–1144, 2018. 1
work page 2018
-
[27]
An analysis of uct in multi-player games
Nathan R Sturtevant. An analysis of uct in multi-player games. InInternational conference on computers and games, pages 37–49. Springer, 2008. 2.4
work page 2008
-
[28]
On pruning techniques for multi-player games.AAAI/IAAI, 49:201– 207, 2000
Nathan R Sturtevant and Richard E Korf. On pruning techniques for multi-player games.AAAI/IAAI, 49:201– 207, 2000. 2.2 Appendix We present in this document the details of the experiments. First, note that theNvalue andCvalue of the neural networks for each game are in Table 7. In Section 4.3, we present the results of our repeated experiment, modifying th...
work page 2000
-
[29]
All players are eliminated: the last player to be eliminated is declared the winner. Scores are assigned by reverse elimination order: last eliminated player scores1, the second last eliminated player scores0, third last player scores−1, and the first eliminated player scores−2
-
[30]
Their score equals the number of legal moves available at termination:s
One player remains: the remaining player is the winner. Their score equals the number of legal moves available at termination:s. The last eliminated player scores0, the second last eliminated player scores−s, and the first eliminated player scores−2s. Note that the associated terminal evaluation that we used is the score of the game. 4.4.7 Quadrothello We...
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.