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An Open Boundary Safety-of-Territory Solver for the Game of Go

Author: Xiaozhen Niu, Martin MuellerDept of Computing Science

University of AlbertaPresented by: Xiaozhen Niu

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Outline Introduction Open Boundary Safety-of-Territory

Solver Forward Pruning Techniques Experimental Results Conclusions and Future Work

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Introduction Problem: In real games, most

territories are not fully enclosed Safety solver 1.0 has several

restrictions: The region has to be completely

enclosed Does not consider external liberties

Goal: estimating the safety of open boundary territories!

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Example

White plays first

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Open Boundary Safety-of-Territory Solver

New features of safety solver 2.0 Input parameters and goal setting Board partitioning Multiple searches for related goals

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New Features Safety solver 2.0 has following new

features: Search goals customized by different

parameters Multi-searches to provide solutions for

different goals Integration with full-board play in

Explorer

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Input parameters (1) A set of points (area) The color of the defender and attacker The color of the first player Boundary safe or territory safe?

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Input parameters (2) Handle Seki External Liberties Who is the ko winner?

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Search Goal Setting Safety solver 2.0 concentrates on

proving area safe locally Does not consider connection

problems Default search goal:

Prove territory safe Handle seki Count external liberties No ko winner needs to be set initially

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Board Partitioning Zone computing Zone merging

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Zone Computing Use heuristic territory evaluation to

partition the board into zones Zones are computed by using

dividers, potential dividers

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Zone Merging Two zones are related if they share

one or more common boundary blocks

Safety solver 2.0 extends the merging algorithm for enclosed zones by dealing with dividers

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Example

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Multiple Searches for Related Goals

Switching which player plays first

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Multiple Searches for Related Goals (2)

Determining when external liberties affect the safety status of an area

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Integration with Explorer Generate defending or invading

move for zones Set move values by heuristics

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Forward Pruning Techniques Two techniques for the defender:

External moves Inner eyes

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External Moves In a 12 interior points zone. Generate

20 moves for the attacker and 16 moves for the defender

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Inner Eyes Inner eyes can be pruned for

the defender

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Experimental Results Two test sets.

Set one: most from classic Guan Zi Pu. 60 main problem and 60 modified problems that has some external liberties added

Set two: 20 problems from computer game play records

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Test Set 1: Correctness Test

Four Examples from set 1

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Test Set 2: Game Play Test Goal: to test whether Explorer enhanced

by the safety solver 2.0 is able to play the correct defending or invading move

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Conclusions Safety solver 2.0 can provide

evaluations for the safety status of open boundary areas

Major limitation: size of the open area (current: 15)

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Future Work: Flexible time control scheme using

heuristics to select suitable problems to solve

Get best try move Integrate other tactical solvers Measure playing strength

improvements