Comparison and optimisation of search algorithms exemplified by abstract game Yinsh

Neža Belej (2017) Comparison and optimisation of search algorithms exemplified by abstract game Yinsh. MSc thesis.

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Abstract

In the thesis we analyse search algorithms that are able to find solutions for abstract board games. We choose the game Yinsh, one of the well known project Gipf games. The goal of the thesis is to find and implement a Yinsh-playing program that is able to defeat all the available computer programs and is strong against experienced human players. As a base method we choose Minimax, for which we implement various gradually upgrading evaluation functions. We analyse the constants in those functions and find the best combinations of them empirically. Because Yinsh has a large branching factor, basic Minimax is not an optimal solution. Based on the nature of the game Yinsh we propose multiple optimisations of the Minimax method, which we implement, test and evaluate. We also implement Monte-Carlo Tree Search method for the game Yinsh and compare its performance to the Minimax based algorithms. Based on the analysed approaches we compose the final solution. We also propose improvements and future work. Our final solution produces very good results. It defeats multiple computer programs and is also strong against experienced human players.

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