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

Introduction Analysis of Typical Josekis Case Studies

Handtalk Wulu Goemate

Conclusions

3

Introduction

A quantitative estimation of the outward influence is important

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

“Moku” is used as the unit of territory in this paper.

“moku” and “point” on the board

6

Analysis of Typical Josekis

Josekis are sequences leading to an approximately even result

A typical 3-4 joseki

7

A Typical 3-4 Joseki

In the basic joseki, black still has some thinness.

8

A Typical 3-4 Joseki (2)

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

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

10

Another 3-4 Joseki

Black has about 10 mokus, while white has about 3 mokus, the difference in height is 2 lines.

11

Case Studies

HandTalk Wulu Goemate

12

HandTalk Influence calculation is restricted to some

specified neighboring points. 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

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)

If absolute value of sum < 2, ignore, else if <6, set to temporary influence, else set to full influence

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 Sum of the black influence is 25.5 mokus, while the

white is 29 mokus Sum of the black influence is 26 and 1/6 mokus,

while the white is 23.5 mokus B, C, E, F stand for 2, 3, 5 and 6 expressed in 1/6

moku

A derivative from 3-4 joseki A derivative from 4-4 joseki

15

Wulu

Wulu uses entirely different scheme to calculate influence

Degree 1 1.5 2 2.5White influence 6 5 3 2Black influence -6 -5 -3 -2

16

Examples 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. 24.5 mokus for black and 16.5 for white.

17

Goemate

Improved scheme of screening (blocking) Three cases in screening:

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 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)

Case 3: half-screened

20

Two Rules

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

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 Improved screening scheme get more

accurate calculation results

Black influence: 21 and 2/3White influence: 24 and 1/3

Black influence: 21 and 2/3White influence: 21 and 1/6

22

Conclusions

Developed a rule for measuring the outward influence radiated by a wall standing on an edge

Should be an increase of 3 mokus for the increase of one line of the height

Improved screening scheme in Goemate gives good results of outward influence calculation