int search_uct(int color, int node_n)
{
NODE *pN = &node[node_n];
CHILD *c = NULL;
int select, z, err, win, current_depth;
for (;;) {
select = select_best_ucb(node_n, color);
c = &pN->child[select];
z = c->z;
err = put_stone(z, color, FILL_EYE_ERR);
if ( err == 0 ) break;
c->z = ILLEGAL_Z; // select other move
}
current_depth = depth;
path[depth++] = c->z;
// playout in first time. <= 10 can reduce node.
if ( c->games <= 0 || depth == D_MAX || (c->z == 0 && depth>=2 && path[depth-2]==0) ) {
win = -playout(flip_color(color));
} else {
if ( c->next == NODE_EMPTY ) c->next = create_node(c->z);
win = -search_uct(flip_color(color), c->next);
}
update_rave(pN, color, current_depth, win);
// update winrate
c->rate = (c->rate * c->games + win) / (c->games + 1);
c->games++;
pN->child_games_sum++;
return win;
}
void Player::PlayerUCT::walk_tree(Board & board, Node * node, int depth){
int toplay = board.toplay();
if(!node->children.empty() && node->outcome < 0){
//choose a child and recurse
Node * child;
do{
int remain = board.movesremain();
child = choose_move(node, toplay, remain);
if(child->outcome < 0){
movelist.addtree(child->move, toplay);
if(!board.move(child->move, (player->minimax == 0), (player->locality || player->weightedrandom) )){
logerr("move failed: " + child->move.to_s() + "\n" + board.to_s(false));
assert(false && "move failed");
}
child->exp.addvloss(); //balanced out after rollouts
walk_tree(board, child, depth+1);
child->exp.addv(movelist.getexp(toplay));
if(!player->do_backup(node, child, toplay) && //not solved
player->ravefactor > min_rave && //using rave
node->children.num() > 1 && //not a macro move
50*remain*(player->ravefactor + player->decrrave*remain) > node->exp.num()) //rave is still significant
update_rave(node, toplay);
return;
}
}while(!player->do_backup(node, child, toplay));
return;
}
if(player->profile && stage == 0){
stage = 1;
timestamps[1] = Time();
}
int won = (player->minimax ? node->outcome : board.won());
//if it's not already decided
if(won < 0){
//create children if valid
if(node->exp.num() >= player->visitexpand+1 && create_children(board, node, toplay)){
walk_tree(board, node, depth);
return;
}
if(player->profile){
stage = 2;
timestamps[2] = Time();
}
//do random game on this node
for(int i = 0; i < player->rollouts; i++){
Board copy = board;
rollout(copy, node->move, depth);
}
}else{
movelist.finishrollout(won); //got to a terminal state, it's worth recording
}
treelen.add(depth);
movelist.subvlosses(1);
if(player->profile){
timestamps[3] = Time();
if(stage == 1)
timestamps[2] = timestamps[3];
stage = 3;
}
return;
}
