stellar

negamax alpha beta skeleton

1 files changed, 92 insertions(+), 14 deletions(-)

diff --git a/ src/engine.c b/ src/engine.c

@@ -50,6 +50,15 @@ void Move_print(Move move) { Move_enpassant(move) ? 1 : 0, Move_castle(move) ? 1 : 0); }

void Move_print_UCI(Move move) {

int prom;

printf("%s%s", square_to_coordinates[Move_source(move)],

square_to_coordinates[Move_target(move)]);

if ((prom = Move_promote(move)))

printf(" %c", Piece_asci(Piece_fromIndex(prom)));

}

typedef struct MoveList_T *MoveList_T; struct MoveList_T { Move moves[256];

@@ -439,13 +448,84 @@ int evaluate(CBoard_T board) { } }

return side == WHITE ? score : -score;

return score;

}

int ply;

int best_move;

int negamax(CBoard_T board, int alpha, int beta, int depth) {

MoveList_T moves;

CBoard_T backup;

// tmp

Move best;

int old_alpha = alpha;

if (depth == 0) {

return evaluate(board);

}

nodes++;

backup = CBoard_new();

moves = generate_moves(board, NULL);

int legal_moves = 0;

for (int i = 0; i < moves->count; i++) {

CBoard_copy(board, backup);

ply++;

if (make_move(board, moves->moves[i], 0) == 0) {

CBoard_copy(backup, board);

ply--;

continue;

}

legal_moves++;

int score = -negamax(board, -beta, -alpha, depth - 1);

CBoard_copy(backup, board);

ply--;

if (score >= beta) {

MoveList_free(&moves);

CBoard_free(&backup);

return beta;

}

if (score > alpha) {

alpha = score;

if (ply == 0)

best = moves->moves[i];

}

}

if (legal_moves == 0) {

if (CBoard_isCheck(board))

return -49000 + ply;

else

return 0;

}

if (old_alpha != alpha)

best_move = best;

MoveList_free(&moves);

CBoard_free(&backup);

return alpha;

}

void search_position(CBoard_T cboard, int depth) {

(void)cboard;

(void)depth;

printf("bestmove d7d5\n");

void search_position(CBoard_T board, int depth) {

best_move = 0;

int score = negamax(board, -5000000, 5000000, depth);

if (best_move) {

printf("info score cp %d depth %d nodes %ld\n", score, depth, nodes);

printf("bestmove ");

Move_print_UCI(best_move);

printf("\n");

}

} void print_info(void) {

@@ -580,13 +660,14 @@ CBoard_T Instruction_parse(Instruction_T self, CBoard_T board) { if (strcmp(token, "go") == 0) { token = Instruction_token_next(self);

int depth = 6;

if (token && strcmp(token, "depth") == 0) { token = Instruction_token_next(self);

search_position(board, atoi(token));

depth = atoi(token);

} else {

search_position(board, 6);

printf("Unknown argument after go\n"); }

search_position(board, depth);

continue; }

@@ -632,17 +713,14 @@ void uci_loop(void) { int main(void) { init_all();

int debug = 1;

int debug = 0;

if (debug) { printf("debugging!\n");

CBoard_T board = NULL;

CBoard_T board = NULL;

Instruction_T inst = NULL;

board = CBoard_fromFEN(board, start_position);

make_move(board, parse_move(board, "e2e4"), 0);

make_move(board, parse_move(board, "b7b6"), 0);

make_move(board, parse_move(board, "d2d4"), 0);

make_move(board, parse_move(board, "c8b7"), 0);

CBoard_print(board);

printf("Evaluation: %d\n", evaluate(board));

search_position(board, 5);

} else uci_loop(); return 0;