1. 1 Evaluation of strings in computer Go using APC and Seki judgement Author: Hyun-Soo Park and Kyung-Woo Kang Presented by: Xiaozhen Niu

2. 2 Outline Introduction String Graph (SG) Rules Experiments Summary

3. 3 Introduction Problem: life-and-death of strings Major issues: Infeasible by brute-force search Goal: using string graph (SG) and related rules to determine life and death status

4. 4 Basic Structure

5. 5 String Graph (SG) A string graph (SG) can be defined as follows: SG = (V, E) V = {BS, WS, ES} E = {Ed, Eu}, Eu: adjacency relationship, Ed: inclusion relationship.

6. 6 Examples (1) A directed edge: An undirected edge:

7. 7 Euclidean distance based Clustering Calculate distances between the input pattern and the weighted center of each cluster Find the closest cluster within the range of the threshold P

8. 8 Examples

9. 9 Examples (2) An Alive String Graph (ASG):

10. 10 Rules Rule 1: APC: articulation point check Articulation point: if removed the rest of the graph becomes disconnected. Using the number of AP and number of empty points to decide the life and death status

11. 11 Examples (1) Empty points = 6, AP = 0: Empty points = 6, AP = 4, 3, 2:

12. 12 Examples (2) Empty points = 6, AP = 1: Empty points = 7, AP = 1:

13. 13 Evaluation of Seki OSOG: one string and one group S1 and S2 are OSOG, S3 does not need to be OSOG, but with same color of S1

14. 14 Judgment of Seki (JOS) JOS: S2 are surrounded by S3 and without external liberties S1 is OSOG, included in S2 2 empties (e1, e2) in S2 Procedure: Add one stone of s1 in e1 and e2 separately can create new string s4, s5, if s4, s5 are both alive by APC, S1 and S2 are seki. Else, S1 is alive, S2 is dead, e1 and e2 belong to S1

15. 15 Examples Seki: No seki:

16. 16 Evaluation of Stability of Strings

17. 17 Experiments Using IGS_31_counted problems, includes 11,191 points and 1,123 strings

18. 18 Examples

19. 19 Summary Using SG and related rules for static evaluation Advantages: APC can be used to determine small area (size <7) Disadvantages: too optimistic to use in larger area (size >7)! JOS can’t determine if strings are not OSOG