1 Influence Calculation in Go Paper: Semi-empirical Quantitative Theory of GO Part 1: Estimation of the Influence of a Wall ICGA Journal Vol.25 No.4 December 2002 Authors: Zhixing Chen Presented by: Niu Xiaozhen

2 Outline n Introduction n Analysis of Typical Josekis n Case Studies u Handtalk u Wulu u Goemate n Conclusions

3 Introduction n A quantitative estimation of the outward influence is important n The amount of influence is related to its potential to obtain territory

4 Introduction (2) I. Game-tree search for string capture and escape II. Evaluation Function IV. Move point choice Influence III. Calculation of move values Block Recognition Block Data Freedom... Eye Recognition V. Move efficiency by pattern recognition VI. Joseki and fuseki management

5 Moku n “Moku” is used as the unit of territory in this paper. “moku” and “point” on the board

6 Analysis of Typical Josekis n Josekis are sequences leading to an approximately even result A typical 3-4 joseki

7 A Typical 3-4 Joseki n In the basic joseki, black still has some thinness.

8 A Typical 3-4 Joseki (2) n Assuming the black’s territory is confined to the boundary marked by x, it has 17 mokus, white is assumed to have only 1 mokus. Conclusion: there should be 3 mokus per line of height!

9 A 4-4 Joseki n Here is a derivative from a 4-4 joseki. Black has 14 mokus, but white are 4 lines higher.

10 Another 3-4 Joseki n Black has about 10 mokus, while white has about 3 mokus, the difference in height is 2 lines.

11 Case Studies n HandTalk n Wulu n Goemate

12 HandTalk n Influence calculation is restricted to some specified neighboring points. n The unit of the value is 1/6 moku, so 6 is 1 moku, 2 is 1/3 moku, 3 is 1/2 moku, 5 is 5/6 moku etc.

13 Several Schemes in Calculation n Boundary adjustment: points in line 1 or 2 receiving influence by only white stones add some value (add 2 for line 1, add 1 for line 2) n If absolute value of sum < 2, ignore, else if <6, set to temporary influence, else set to full influence n Smoothing scheme: if a point with 6 is directly adjacent to a point with 0, reduced to 3; if directly adjacent to a point with 2, reduce to 5;

14 Examples n Sum of the black influence is 25.5 mokus, while the white is 29 mokus n Sum of the black influence is 26 and 1/6 mokus, while the white is 23.5 mokus n B, C, E, F stand for 2, 3, 5 and 6 expressed in 1/6 moku A derivative from 3-4 josekiA derivative from 4-4 joseki

15 Wulu n Wulu uses entirely different scheme to calculate influence

16 Examples n Wulu often underestimates the outward influence because it only calculates 2 degrees. Influence restricted in two rows, 24.5 for black and 14 for white, the error exceeds 10 mokus Outward influence is still too low mokus for black and 16.5 for white.

17 Goemate n Improved scheme of screening (blocking) n Three cases in screening: u case 1: for the influence of a stone on a diagonal adjacent destination point, a stone directly adjacent to both the stone and the destination point half-screens the influence

18 Three cases in screening n Case 2: for a destination point beyond adjacent and diagonal adjacent, draw a line from the stone to the destination, the influence will be fully screened if any other stone is on the line.

19 Three cases in screening (2) n Case 3: half-screened

20 Two Rules n Rule 1: if the influence of a stone on a destination point is half- screened by more than 1 other stones, it will be fully screened n Rule 2: if the influence of a stone on a point is half-screened by a stone of the same color or by an injured stone of the opposite color, it will not be screened

21 Examples n Improved screening scheme get more accurate calculation results Black influence: 21 and 2/3 White influence: 24 and 1/3 Black influence: 21 and 2/3 White influence: 21 and 1/6

22 Conclusions n Developed a rule for measuring the outward influence radiated by a wall standing on an edge n Should be an increase of 3 mokus for the increase of one line of the height n Improved screening scheme in Goemate gives good results of outward influence calculation