// Evaluate the move by performing a search.
void evaluateMove(searchNode *node, move_t mv, move_t killer_a,
move_t killer_b, searchType_t type,
uint64_t *node_count_serial, moveEvaluationResult* result) {
int ext = 0; // extensions
bool blunder = false; // shoot our own piece
result->next_node.subpv[0] = 0;
result->next_node.parent = node;
// Make the move, and get any victim pieces.
bool isko = make_move(&(node->position), &(result->next_node.position), mv);
// Check whether this move changes the board state.
// such moves are not legal.
if (isko) {
result->type = MOVE_ILLEGAL;
return;
}
victims_t* victims = &result->next_node.position.victims;
// Check whether the game is over.
if (is_game_over(victims, node->pov, node->ply)) {
// Compute the end-game score.
result->type = MOVE_GAMEOVER;
result->score = get_game_over_score(victims, node->pov, node->ply);
return;
}
// Ignore noncapture moves when in quiescence.
if (zero_victims(victims) && node->quiescence) {
result->type = MOVE_IGNORE;
return;
}
// Check whether the board state has been repeated, this results in a draw.
if (is_repeated(&(result->next_node.position), node->ply)) {
result->type = MOVE_GAMEOVER;
result->score = get_draw_score(&(result->next_node.position), node->ply);
return;
}
tbassert(victims->stomped == 0
|| color_of(victims->stomped) != node->fake_color_to_move,
"stomped = %d, color = %d, fake_color_to_move = %d\n",
victims->stomped, color_of(victims->stomped),
node->fake_color_to_move);
// Check whether we caused our own piece to be zapped. This isn't considered
// a blunder if we also managed to stomp an enemy piece in the process.
if (victims->stomped == 0 &&
victims->zapped > 0 &&
color_of(victims->zapped) == node->fake_color_to_move) {
blunder = true;
}
// Do not consider moves that are blunders while in quiescence.
if (node->quiescence && blunder) {
result->type = MOVE_IGNORE;
return;
}
// Extend the search-depth by 1 if we captured a piece, since that means the
// move was interesting.
if (victim_exists(victims) && !blunder) {
ext = 1;
}
// Late move reductions - or LMR. Only done in scout search.
int next_reduction = 0;
if (type == SEARCH_SCOUT && node->legal_move_count + 1 >= LMR_R1 && node->depth > 2 &&
zero_victims(victims) && mv != killer_a && mv != killer_b) {
if (node->legal_move_count + 1 >= LMR_R2) {
next_reduction = 2;
} else {
next_reduction = 1;
}
}
result->type = MOVE_EVALUATED;
int search_depth = ext + node->depth - 1;
// Check if we need to perform a reduced-depth search.
//
// After a reduced-depth search, a full-depth search will be performed if the
// reduced-depth search did not trigger a cut-off.
if (next_reduction > 0) {
search_depth -= next_reduction;
int reduced_depth_score = -scout_search(&(result->next_node), search_depth,
node_count_serial);
if (reduced_depth_score < node->beta) {
result->score = reduced_depth_score;
return;
}
search_depth += next_reduction;
}
// Check if we should abort due to time control.
if (abortf) {
result->score = 0;
result->type = MOVE_IGNORE;
return;
}
if (type == SEARCH_SCOUT) {
result->score = -scout_search(&(result->next_node), search_depth,
node_count_serial);
} else {
if (node->legal_move_count == 0 || node->quiescence) {
result->score = -searchPV(&(result->next_node), search_depth, node_count_serial);
} else {
result->score = -scout_search(&(result->next_node), search_depth,
node_count_serial);
if (result->score > node->alpha) {
result->score = -searchPV(&(result->next_node), node->depth + ext - 1, node_count_serial);
}
}
}
}
score_t searchRoot(position_t *p, score_t alpha, score_t beta, int depth,
int ply, move_t *pv, uint64_t *node_count_serial,
FILE *OUT) {
static int num_of_moves = 0; // number of moves in list
// hopefully, more than we will need
static sortable_move_t move_list[MAX_NUM_MOVES];
if (depth == 1) {
// we are at depth 1; generate all possible moves
num_of_moves = generate_all_opt(p, move_list, false);
// shuffle the list of moves
for (int i = 0; i < num_of_moves; i++) {
int r = myrand() % num_of_moves;
sortable_move_t tmp = move_list[i];
move_list[i] = move_list[r];
move_list[r] = tmp;
}
}
searchNode rootNode;
rootNode.parent = NULL;
initialize_root_node(&rootNode, alpha, beta, depth, ply, p);
assert(rootNode.best_score == alpha); // initial conditions
searchNode next_node;
next_node.subpv[0] = 0;
next_node.parent = &rootNode;
score_t score;
for (int mv_index = 0; mv_index < num_of_moves; mv_index++) {
move_t mv = get_move(move_list[mv_index]);
if (TRACE_MOVES) {
print_move_info(mv, ply);
}
(*node_count_serial)++;
// make the move.
victims_t x = make_move(&(rootNode.position), &(next_node.position), mv);
if (is_KO(x)) {
continue; // not a legal move
}
if (is_game_over(x, rootNode.pov, rootNode.ply)) {
score = get_game_over_score(x, rootNode.pov, rootNode.ply);
next_node.subpv[0] = 0;
goto scored;
}
if (is_repeated(&(next_node.position), rootNode.ply)) {
score = get_draw_score(&(next_node.position), rootNode.ply);
next_node.subpv[0] = 0;
goto scored;
}
if (mv_index == 0 || rootNode.depth == 1) {
// We guess that the first move is the principle variation
score = -searchPV(&next_node, rootNode.depth-1, node_count_serial);
// Check if we should abort due to time control.
if (abortf) {
return 0;
}
} else {
score = -scout_search(&next_node, rootNode.depth-1, node_count_serial);
// Check if we should abort due to time control.
if (abortf) {
return 0;
}
// If its score exceeds the current best score,
if (score > rootNode.alpha) {
score = -searchPV(&next_node, rootNode.depth-1, node_count_serial);
// Check if we should abort due to time control.
if (abortf) {
return 0;
}
}
}
scored:
// only valid for the root node:
tbassert((score > rootNode.best_score) == (score > rootNode.alpha),
"score = %d, best = %d, alpha = %d\n", score, rootNode.best_score, rootNode.alpha);
if (score > rootNode.best_score) {
tbassert(score > rootNode.alpha, "score: %d, alpha: %d\n", score, rootNode.alpha);
rootNode.best_score = score;
pv[0] = mv;
memcpy(pv+1, next_node.subpv, sizeof(move_t) * (MAX_PLY_IN_SEARCH - 1));
pv[MAX_PLY_IN_SEARCH - 1] = 0;
// Print out based on UCI (universal chess interface)
double et = elapsed_time();
char pvbuf[MAX_PLY_IN_SEARCH * MAX_CHARS_IN_MOVE];
getPV(pv, pvbuf, MAX_PLY_IN_SEARCH * MAX_CHARS_IN_MOVE);
if (et < 0.00001) {
et = 0.00001; // hack so that we don't divide by 0
}
uint64_t nps = 1000 * *node_count_serial / et;
fprintf(OUT, "info depth %d move_no %d time (microsec) %d nodes %" PRIu64
" nps %" PRIu64 "\n",
depth, mv_index + 1, (int) (et * 1000), *node_count_serial, nps);
fprintf(OUT, "info score cp %d pv %s\n", score, pvbuf);
// Slide this move to the front of the move list
for (int j = mv_index; j > 0; j--) {
move_list[j] = move_list[j - 1];
}
move_list[0] = mv;
}
// Normal alpha-beta logic: if the current score is better than what the
// maximizer has been able to get so far, take that new value. Likewise,
// score >= beta is the beta cutoff condition
if (score > rootNode.alpha) {
rootNode.alpha = score;
}
if (score >= rootNode.beta) {
tbassert(0, "score: %d, beta: %d\n", score, rootNode.beta);
break;
}
}
return rootNode.best_score;
}