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Topic: Board representation in Bomb (Read 815 times) |
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fotland
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Arimaa player #211
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Board representation in Bomb
« on: Feb 11th, 2007, 5:43pm » |
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Bomb uses one bitmap for each piece type with a bit set for each square containing that piece. It also has an array for the board giving the piece on each square. This is a single dimension array since a two dimension array would be slower.
It tracks the strongest piece adjacent to each square, and has a bitmap for pieces that are frozen.
It has a 64-bit zobrist hash used to detect repetiion and to index into the transposition table during search.
It keeps track of the current step and push/pull status.
It has some incremental evaluation values, for material balance, and number of rabbits for each side.
The full board data structue is:
bmap p[NUMBITMAPS]; // locations of pieces, by PIECE NAMES (inluding one for empty squares)
bmap frozen; // bit set if that piece is frozen
char pieces[64]; // piece on each point, 0 is upper left (black side of board )
char strongest[2][64]; // strongest piece next to each square, by color (or EMPTY)
unsigned int hashindex, hashkey1; // transposition table values
int material; // material balance, 1000 per pawn, positive for gold
int bestmateval; // best pawn matestep value
char bestmateloc; // best mate location
char tm; // side to move (0-white, 1-black)
char phase; // phase of the the move, 0-3
char wtotmat, btotmat; // white and black total material, 1, 2, 3, 5, 9, 11
unsigned char pullsquare, pullpiece; // last move's pulling square (empty square where piece was)
// and piece doing the pulling - unless pullpiece is empty
unsigned char pushsquare, pushpiece; // last move pushed square (empty point where piece was)
// and enemy piece that was pushed -
// unless pushpiece is empty - next step is forced
unsigned char pawncount[2]; // how many pawns left by color
char matesearch; // doing a mate search now
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| « Last Edit: Feb 11th, 2007, 6:31pm by fotland » |
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fotland
Forum Guru
Arimaa player #211
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Posts: 216
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Re: Board representation in Bomb
« Reply #1 on: Feb 11th, 2007, 5:46pm » |
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When doing a search we have to make a move, evaluate (possibly with more search), and unmake the move. I find it fastest to only write code for making the move. During search I make a copy of the board before making a move, so unmaking a move is not needed. This saves a lot of code to do incremental unmakes, and since the board data is small, the copy takes very little time.
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