stellar

UCI Chess engine written in C++20
git clone git://git.dimitrijedobrota.com/stellar.git
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commit 7e7b1f3d78e9ea7f09b3f992d5025df7499bdd8e
parent 6a099774bbf1cedae98b3dcfdf3a248938aa2646
author Dimitrije Dobrota < mail@dimitrijedobrota.com >
date Sat, 1 Oct 2022 21:22:10 +0200

Principle Variation

Diffstat:
M src/engine.c | ++++++++++++++++++++++++++ ----------------------

1 files changed, 26 insertions(+), 22 deletions(-)

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

@@ -464,8 +464,10 @@ int evaluate(CBoard_T board) {

return score;
}

int pv_length[64];
Move pv_table[64][64];

int ply;
int best_move;
int killer_moves[2][64];
int history_moves[16][64];

@@ -555,9 +557,7 @@ int negamax(CBoard_T board, int alpha, int beta, int depth) {

CBoard_T copy;
int isCheck = 0;

// tmp
Move best;
int old_alpha = alpha;
pv_length[ply] = ply;

if (depth == 0)
return quiescence(board, alpha, beta);

@@ -571,22 +571,20 @@ int negamax(CBoard_T board, int alpha, int beta, int depth) {

if (isCheck)
depth++;

MoveList_sort(board, list);

int legal_moves = 0;
MoveList_sort(board, list);
for (int i = 0; i < list->count; i++) {
Move move = list->moves[i];
CBoard_copy(board, copy);
ply++;

CBoard_copy(board, copy);
if (make_move(copy, move, 0) == 0) {
ply--;
continue;
}

legal_moves++;

int score = -negamax(copy, -beta, -alpha, depth - 1);
legal_moves++;
ply--;

if (score >= beta) {

@@ -600,11 +598,15 @@ int negamax(CBoard_T board, int alpha, int beta, int depth) {

}

if (score > alpha) {
/* if (!Move_capture(move)) */
history_moves[Piece_index(Move_piece(move))][Move_target(move)] += depth;
if (!Move_capture(move))
history_moves[Piece_index(Move_piece(move))][Move_target(move)] +=
depth;
alpha = score;
if (ply == 0)
best = move;

pv_table[ply][ply] = move;
for (int i = ply + 1; i < pv_length[ply + 1]; i++)
pv_table[ply][i] = pv_table[ply + 1][i];
pv_length[ply] = pv_length[ply + 1];
}
}

@@ -615,9 +617,6 @@ int negamax(CBoard_T board, int alpha, int beta, int depth) {

return 0;
}

if (old_alpha != alpha)
best_move = best;

MoveList_free(&list);
CBoard_free(&copy);
return alpha;

@@ -626,12 +625,17 @@ int negamax(CBoard_T board, int alpha, int beta, int depth) {

void search_position(CBoard_T board, int depth) {
int score = negamax(board, -50000, 50000, 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");
printf("info score cp %d depth %d nodes %ld pv ", score, depth, nodes);

for (int i = 0; i < pv_length[0]; i++) {
Move_print_UCI(pv_table[0][i]);
printf(" ");
}
printf("\n");

printf("bestmove ");
Move_print_UCI(pv_table[0][0]);
printf("\n");
}

void print_info(void) {

@@ -828,7 +832,7 @@ int main(void) {

(void)inst;
(void)list;

board = CBoard_fromFEN(board, killer_position);
board = CBoard_fromFEN(board, tricky_position);
CBoard_print(board);
search_position(board, 5);
} else