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uct.c
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uct.c
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#include "uct.h"
Arena * UCT_NODE_ARENA;
int uct_initialize() {
UCT_NODE_ARENA = arena_new(sizeof(UCTNode), 10000000);
return 1;
}
int uct_destroy() {
arena_free(UCT_NODE_ARENA);
return 1;
}
UCTNode * uct_node_new(Pos pos) {
UCTNode * self = (UCTNode *)arena_calloc(UCT_NODE_ARENA);
self->move = pos;
return self;
}
void uct_node_free(UCTNode * self) {
if(self->child) uct_node_free(self->child);
if(self->next) uct_node_free(self->next);
arena_dealloc(UCT_NODE_ARENA, (void *) self);
}
void uct_node_free_except(UCTNode * self, UCTNode * subtree) {
if(self->child && self->child != subtree)
uct_node_free_except(self->child, subtree);
if(self->next && self->next != subtree)
uct_node_free_except(self->next, subtree);
arena_dealloc(UCT_NODE_ARENA, (void *) self);
}
int create_children(UCTNode * self, Board * board, Color color) {
Pos pos;
Color * goban = board->goban;
UCTNode * ptr, * t;
ptr = 0;
LOOP(pos, SIZE * SIZE) {
if(goban[pos] == EMPTY && !is_eye(goban, pos, color)) {
t = ptr;
ptr = uct_node_new(pos);
ptr->next = t;
}
}
self->child = ptr;
return 1;
}
UCTNode * uct_select(UCTNode * self, Board * board, Color color) {
UCTNode * ptr, * best_ptr;
float uct, best_uct = 0;
while(1) {
best_uct = 0;
best_ptr = 0;
for(ptr = self->child; ptr; ptr = ptr->next) {
if(ptr->move == nil) continue;
if(ptr->visits == 0)
uct = 10000. + (rand() & 0xFF);
else {
uct = UCT_K * sqrtf(
logf(self->visits) / ptr->visits
) + 1.0 * ptr->wins / ptr->visits;
}
if(uct > best_uct) {
best_uct = uct;
best_ptr = ptr;
}
}
if(board_play(board, best_ptr->move, color)) break;
else best_ptr->move = nil;
}
return best_ptr;
}
int uct_play_random_game(Board * board, Color color) {
Color winner;
Board * clone = board_clone(board);
playout_random_game(clone, color);
winner = playout_find_winner(clone);
board_free(clone);
return winner == color;
}
int uct_simulate(UCTNode * self, Board * board, Color color) {
int result;
Pos move;
UCTNode * ptr;
if(!self->child && self->visits < UCT_MIN_VISITS)
result = uct_play_random_game(board, color);
else {
if(!self->child) create_children(self, board, color);
ptr = uct_select(self, board, color);
result = 1 - uct_simulate(ptr, board, color_other(color));
}
self->visits ++;
self->wins += 1 - result;
return result;
}
Pos uct_best_move(UCTNode * self) {
UCTNode * ptr, * best_ptr = 0;
int most_visits = 0;
Pos best_move = nil;
for(ptr = self->child; ptr; ptr = ptr->next) {
if(ptr->move == nil) continue;
if(ptr->visits > most_visits) {
most_visits = ptr->visits;
best_ptr = ptr;
}
}
best_move = best_ptr->move;
printf("BEST_MOVE: [%d %d] %.2f%%\n",
best_move / SIZE, best_move % SIZE,
100.0 * best_ptr->wins / best_ptr->visits
);
return best_move;
}
Pos uct_search(Board * board, Color color) {
int i;
UCTNode * root, * ptr;
Board * clone;
Pos best_move;
root = uct_node_new(nil);
create_children(root, board, color);
LOOP(i, UCT_SIMULATIONS) {
clone = board_clone(board);
uct_simulate(root, clone, color);
//board_print(clone, stdout);
board_free(clone);
}
best_move = uct_best_move(root);
uct_node_free(root);
return best_move;
}