october 28th 2001gpw20011 using castle and assault maps for guiding opening and middle game play in...

October 28th 2001 GPW2001 1

Using Castle and Assault Maps for Guiding Opening and Middle Game Play in Sh

ogi

Reijer Grimbergen (Saga University)

Jeff Rollason (Oxford Softworks)


An Opening Book for Shogi

In two-player complete information games an opening book is used to guide the program in the early stage of the game

The opening book of SPEAR: 1000+ professional games

More than 20 books on joseki

Problem: the number of expert players is relatively small, therefore

The number of publicly available expert games is small

The number of books on opening play is small

More than 110,000 positions


Using the Opening Book in Practice

Opening book test: 25 games against AI Shogi 2000, Kakinoki Shogi IV, Todai Shogi 2 and Kanazawa Shogi 98:

0

5

10

15

20

25

30

1 3 5 7 9 1113151719212325

Game Number

Mov

e N

umbe

r

AI Shogi

Kakinoki Shogi

KanazawaShogiTodai Shogi 2


An Opening Book in Shogi: Results

Our program gets out of book quickly:Within five moves in 32 games; within ten moves in 71 games

Average: out of book after 8.5 moves

Conclusion: an opening book is not very useful in shogi


Implementation of Castle MapsShogi has a slow build-up

There are many different castles formations and ways to assault these castlesMost formations take a number of moves to buildFormations can have different stages

Idea: use board maps of castle formations and assault formations to guide opening and middle game play


Data Structure for Board Maps

char **castles[] = {mino, a_mino, id_st

atic,

high_mino, a_mino, id_static,

silver_crown, a_mino, id_static,

boat, a_boat, id_ranging,

};


Piece Definition Data Structurechar *mino[] = {

// Non-promoted pieces // Promoted piecesmino_pawn, mino_gold,mino_lance, mino_gold,mino_knight, mino_gold,mino_silver, mino_gold,mino_gold, void,mino_bishop, mino_bishop,mino_rook, mino_rook,mino_king, void,

“Mino”};


Square Values for Each Piece char mino_king[] = { -9,-9,-9,-9,-9,-9,-9,-9,-9,

-9,-9,-9,-9,-9,-9,-9,-9,-9, -9,-9,-9,-9,-9,-9,-9,-9,-9, -9,-9,-9,-9,-9,-9,-9,-9,-9, -9,-9,-9,-9,-9,-9,-9,-9,-9, -9,-9,-9,-9,-8,-1,-1,-1,-1, -9,-9,-9,-9,-7, 0, 4, 8, 5, -9,-9,-9,-8,-6, 2, 8,14, 6, -9,-9,-9,-7,-5,-1, 8, 8, 6

} ;


Strategic Guidance using Piece MapsHill climbing approach: try to move pieces to squares with a higher valueExample: if the king is on 5i in the current position, the following move sequences are suggested

[K5i-K4h-K3h-K2h] or [K5i-K4h-K3i-K2h](both paths have values [–5, 2, 8, 14])

Assault mapsThe assault is defined by the opponent’s castleAssault maps are defined in the same way as the castle map in the example

Current implementation: 35 castle formations and 20 assault formations


Using Piece Maps in a Shogi Program

Select a target castleSelect the corresponding assault mapUse of the piece maps:① The evaluation function② To guide the search to the right move order③ Guide the program to a position it can

understand④ Establishing the game stage⑤ Plausible move generation


Results

Match Book Result

10 20 30 40 50

AllMaps

vs

NoMaps

38-12 30-20 27-23 25-25 25-25 145-105

76% 70% 54% 50% 50% 58%

CastleMaps

vs

NoMaps

36-14 31-19 25-25 25-25 23-27 140-110

72% 62% 50% 50% 46% 56%

AllMaps

vs

CastleMaps

27-23 29-21 29-21 29-21 28-22 142-108

54% 58% 58% 58% 56% 57%


Related Work

The otoshiana method (Yamashita 1998) also uses a hill climbing approach for building castles

Only 9 different castle formations

No assault formations

How to assess the opponent position?


Conclusions and Future Work

The use of piece maps significantly improves the playing strength of a shogi program in the early stages of the gameFuture work

Multiple castles during the searchSwapping rules based on positional featuresScaling of castlesAssaults separate from castle formations

october 28th 2001gpw20011 using castle and assault maps for guiding opening and middle game play in...

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