Novel AI strategies for Multi-Player games at intermediate board states

This paper considers the problem of designing efficient AI strategies for playing games at intermediate board states. While general heuristic-based methods are applicable for all boards states, the search required in an alpha-beta scheme depends heavily on the move ordering. Determining the best move ordering to be used in the search is particularly interesting and complex in an intermediate board state, compared to the situation where the game starts with an initial board state, as we do not assume the availability of “Opening book” moves. Furthermore, unlike the two-player scenario that is traditionally analyzed, we investigate the more complex scenario when the game is a multi-player game, like Chinese Checkers. One recent approach, the Best-Reply Search (BRS), resolves this by a process of grouping opponents, which although successful, incurs a very large branching factor. To address this, the authors of this work earlier proposed the Threat-ADS move ordering heuristic, by augmenting the BRS by invoking techniques from the field of Adaptive Data Structures (ADSs) to order the moves. Indeed, the Threat-ADS performs well under a variety of parameters when the game was analyzed at or near the game’s initial state. This work demonstrates that the Threat-ADS also serves as a solution to the unresolved question of finding a viable solution in the far-more variable, intermediate game states. Our present results confirm that the Threat-ADS performs well in these intermediate states for various games. Surprisingly, it, in fact, performs better in some cases, when compared to the start of the game

Enhancing history-based move ordering in game playing using adaptive data structures

This paper pioneers the avenue of enhancing a well-known paradigm in game playing, namely the use of History-based heuristics, with a totally-unrelated area of computer science, the field of Adaptive Data Structures (ADSs). It is a well-known fact that highly-regarded game playing strategies, such as alpha-beta search, benefit strongly from proper move ordering, and from this perspective, the History heuristic is, probably, one of the most acclaimed techniques used to achieve AI-based game playing. Recently, the authors of this present paper have shown that techniques derived from the field of ADSs, which are concerned with query optimization in a data structure, can be applied to move ordering in multi-player games. This was accomplished by ranking opponent threat levels. The work presented in this paper seeks to extend the utility of ADS-based techniques to two-player and multi-player games, through the development of a new move ordering strategy that incorporates the historical advantages of the moves. The resultant technique, the History-ADS heuristic, has been found to produce substantial (i.e, even up to 70%) savings in a variety of two-player and multi-player games, at varying ply depths, and at both initial and midgame board states. As far as we know, results of this nature have not been reported in the literature before

Why Are Computational Neuroscience and Systems Biology So Separate?

Despite similar computational approaches, there is surprisingly little interaction between the computational neuroscience and the systems biology research communities. In this review I reconstruct the history of the two disciplines and show that this may explain why they grew up apart. The separation is a pity, as both fields can learn quite a bit from each other. Several examples are given, covering sociological, software technical, and methodological aspects. Systems biology is a better organized community which is very effective at sharing resources, while computational neuroscience has more experience in multiscale modeling and the analysis of information processing by biological systems. Finally, I speculate about how the relationship between the two fields may evolve in the near future

Novel threat-based AI strategies that incorporate adaptive data structures for multi-player board games

This paper considers the problem of designing novel techniques for multi-player game playing, in a range of board games and configurations. Compared to the well-known case of two-player game playing, multi-player game playing is a more complex problem with unique requirements. To address the unique challenges of this domain, we examine the potential of employing techniques inspired by Adaptive Data Structures (ADSs) to rank opponents based on their relative threats, and using this information to achieve gains in move ordering and tree pruning. We name our new technique the Threat-ADS heuristic. We examine the Threat-ADS’ performance within a range of game models, employing a number of different, well-understood update mechanisms for ADSs. We then extend our analysis to specifically consider intermediate board states, which are more interesting than the initial board state, as we do not assume the availability of “Opening book” moves, and where substantial variation can exist, in terms of available moves and threatening opponents. We expand this analysis to include an exploration of the Threat-ADS heuristic’s performance in deeper ply game trees, to confirm that it maintains its benefits even when lookahead is greater, and with an expanded examination of how the number of players present in the game impacts the performance of the Threat-ADS heuristic. We find that in nearly all environments, the Threat-ADS heuristic is able to produce meaningful, statistically significant improvements in tree pruning, demonstrating that it serves as a very reliable move ordering heuristic for multi-player game playing under a wide range of configurations, thus motivating the use of ADS-based techniques within the field of game playing

On enhancing recent multi-player game playing strategies using a spectrum of adaptive data structures

Multi-Player Game Playing (MPGP) strategies have predominantly been built on the basis of utilizing Two-Player Game Playing (TPGP) strategies that were designed for games such as Chess and Go. However, a few strategies, such as the Best-Reply Search (BRS), that have been specifically tuned for the multi-player setting, have been introduced in the literature. Recently, these strategies have been further optimized by incorporating into them techniques from the field of Adaptive Data Structures (ADS) [1]. In this paper, we extend this area of research by demonstrating the efficacy of a broader spectrum of techniques from the field of ADS. The results presented in [1] have been enhanced in two directions, namely by considering a set of list-based ADSs capable of 'ranking' the relative strengths of the perspective player's opponents, and by also considering the ply-depth to which the ADSs can be invoked. The results that we present conclusively prove that the incorporation of ADSs positively enhances the BRS, that the semantics of the ADS scheme used question can influence its performance, and that the advantage gleaned remains at deeper search depths

Space and depth-related enhancements of the history-ADS strategy in game playing

In the field of game playing, it is a well-known fact that powerful strategies, such as alpha-beta search, benefit strongly from proper move ordering. A popular metric of achieving this is the so-called 'move history', that is, prioritizing moves that have performed well, earlier in the search. The literature reports a number of techniques, such as the Killer Moves and History heuristics, that employ such a philosophy. Inspired by techniques from the field of Adaptive Data Structures (ADSs), we1 have previously introduced the History-ADS heuristic, which uses an adaptive list to record moves, and to improve move ordering based on move history. The History-ADS heuristic has been proven to produce substantial gains in tree pruning in a wide variety of cases. However, it made use of a relatively naive application of an unbounded, single adaptive list. In this work, we attempt to refine the History-ADS heuristic, by examining its performance by constraining the length of its adaptive list, and applying multiple ADSs for each level of the tree. Our results show that the vast majority of the savings from the History-ADS heuristic remain even with a very short list, which can be applied to mitigate the drawbacks of an unbound data structure. Although results for multiple ADSs did not outperform single ADSs, we show that they provide some insight into how similar techniques may be applied in the context of the History-ADS heuristic

Challenging state-of-the-art move ordering with Adaptive Data Structures

The field of game playing is a particularly well-studied area within the context of AI, leading to the development of powerful techniques, such as the alpha-beta search, capable of achieving competitive game play against an intelligent opponent. It is well-known that tree pruning strategies, such as alpha-beta, benefit strongly from proper move ordering, i.e., by searching the best element first. A wide range of techniques have been developed over the years to achieve good move ordering, and improved tree pruning, in the field, in general and in particular, in the alpha-beta search, have been extensively studied. Inspired by the formerly unrelated field of Adaptive Data Structures (ADSs), we had previously introduced the History-ADS technique, which employs an adaptive list to achieve effective and dynamic move ordering, in a domain independent fashion. Our previous results confirmed that it performs well in a very wide range of cases, and in varied types of board games. However, our previous work did not compare the performance of the History-ADS heuristic to any established move ordering strategy. In an attempt to address this problem, we present here a comparison to two well-known, acclaimed strategies, which operate on a similar philosophy to the History-ADS, namely, the History Heuristic, and the Killer Moves technique. We also introduce, in this work, a mechanism by which these established move ordering strategies can be approximated, or directly implemented, in terms of ADSs. We confirm that, in a wide range of two-player and multi-player games, at various points in the game’s progression, the History-ADS performs at least as well as these strategies, and, in fact, outperforms them in the majority of cases

Differences in gait complexity and variability between children with and without Developmental Coordination Disorder

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