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Generalized Threats Search

Generalized Threats Search. Paper Review Paper Author: T. Cazenave Review by: A. Botea. Overview. Motivation Generalized Threats Generalized Threats Search (GTS) Experimental Results Conclusion. Motivation. Threat Search works well in games such as Go or Go-Moku GTS:

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Generalized Threats Search

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  1. Generalized Threats Search Paper Review Paper Author: T. Cazenave Review by: A. Botea

  2. Overview • Motivation • Generalized Threats • Generalized Threats Search (GTS) • Experimental Results • Conclusion

  3. Motivation • Threat Search works well in games such as Go or Go-Moku • GTS: • Generalizes the previously published threat algorithms (Abstract Proof Search, Lambda Search, Iterative Widening, Gradual Abstract Proof Search); • Can be faster than other threat algorithms;

  4. Generalized Trees • Binary trees where players can play multiple moves in a row • Two players: Left & Right • Left branches are Left’s moves • Right branches are Right’s moves

  5. Generalized Threats (GTs) • Generalized Threat: • A set of generalized trees with some special properties • Can be represented as tuples: oi = #of nodes followed by at most i left branches

  6. Examples of GTs

  7. Comparison of GTs • Partial order relationship:

  8. Comparison of GTs (2)

  9. Composition of GTs

  10. Composition of GTs (2)

  11. Verification of GTs • Map GT to a concrete move tree so that Left wins • Check that: • For each left branch there is a winning Left move • For each right branch there are no Right moves that prevent Left from winning • The local search used to verify a GT can be optimized

  12. Optimizing GT verification • At nodes that have left branches only: iterative widening • At nodes with both left and right branches: divide-and-conquer • Use abstract moves • Ex. from Atari-Go: if Right strings have >2 liberties, 2-ply search won’t work

  13. Generalized Threat Search • Alpha-Beta • Use GTs to speed-up search • Forced moves for Right • Ex: move 2 found by a (4,3,0) GT • Forced moves for Left • Ex: move 5 found by a (3,2,0) GT

  14. Example

  15. Experimental Results • Atari-Go on a 6x6 board • Compare: • Alpha-Beta • Lambda Search • Gradual Abstract Proof Search • Generalized Threats Search

  16. Experimental Results

  17. Experimental Results

  18. Experimental Results

  19. Conclusion • Generalized Threat Search: • More general than other threat search algorithms • Also faster • Applied to 6x6 Atari-Go • Future Work: try GTS in other games such as Go, LoA, Phutball, Hex, Shogi, and Chess

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