[gnugo-devel] End game strategy

[SP LEE]

Currently, gnugo enters engame mode when there is no move found of value 
greater than 6. However, there are many typical big end game moves worth 10 
to 30 points. I would think the gnugo should enter end game mode when :
1. All b/w groups are non-critical
2. There is no more invasion chance to either color
3. The only task for both color is to expand or defend territory.

The following situation from the game with go ++ maybe a illustration
  A B C D E F G H J K L M N O P Q R S T
19 . . . . . . . . . . . . . . . . . . . 19
18 . . . . O X X . . . . . . . . . O . . 18
17 . . . . O O X . . . X . O . O . O X . 17
16 . . O + . . X . . + . . . . . O X . . 16
15 . . . . . . . . . . . . . . . . X . . 15
14 . . . . . . . . . O . . . . . . . . . 14
13 . O . . O . O . . . . . . . . . . . . 13
12 . X O . . . . . . O . . . . . X . . . 12
11 . X O O X . . . . . . . . . . . . . . 11     WHITE (O) has captured 0 
stones
10 . O X O . X . . X + . . . . . + . . . 10     BLACK (X) has captured 0 
stones
9 . X X . . . . . . . . . . . . . X . . 9
8 . . . . . . . . . . . . . . . . . . . 8
7 . . X . . . X . . . . . . . . . . . . 7
6 . . . . . O . . . . . . . . O . X . . 6
5 . . . . . . . . . . . . . . . . . . . 5
4 . . . + . X . X . X . . . . . O . O . 4
3 . . . X . . . . . . . . . O . . . . . 3
2 . . . . . . . . . O . . . . . . . . . 2
1 . . . . . . . . . . . . . . . . . . . 1
  A B C D E F G H J K L M N O P Q R S T

I think in this case, gnugo should turn off all minimum accepted value such 
as a J pattern and calculate territory value solidly. Gnugo played S18 which 
doesn't worth much, just due to the minimum accepted value of 13.24.

Furthermore, both the best move of black and the best move of white should 
considered. Using gg_genmove I got the following top moves:

Top moves (white) :
1. M4  17.08
2. E9  16.01
3. M3  14.91
4. M6  14.09
5. L3  13.63
6. N6  11.80
7. M5  11.72
8. M7  10.82
9. N5  10.81
10. N7  10.45

Top moves(black):
1. S18 13.24
2. E9  11.77
3. J16 11.47
4. M5  11.37
5. H2  10.93
6. S5  10.90
7. L6  10.85
8. M4  10.32
9. L7  10.26
10. M3  9.65

Interestingly E9 is valued high for both black and white. Same as M5 and M4. 
Thus gnugo should play E9. There should be cases where black and white's 
moves differ a little bit, but that is still the position of interest.

I'm not sure if the above strategy is feasible. I hope people with better 
knowledge of the software structure of gnugo can make some comments.

SP Lee

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