board min_node(board ¤t, vector <string> &traverse_log, const int depth, const bool prune, const node from, const bool save_log) const {
assert(depth >= 0 && depth <= cutoff);
//cout << get_node_name(current) << endl;
int v = MAX_INT;
/*if (depth == cutoff) {
v = current.eval(who);
}*/
board best = current;
if ((current.who != current.whom && depth == cutoff) || !current.has_legal_move() || (!current.is_root && abs(current.eval(who)) == WINNING)) {
best.val = current.eval(who);
if (save_log) {
traverse_log.push_back(log_string(current, depth, best.val, prune));
}
return best;
}
if (save_log) {
traverse_log.push_back(log_string(current, depth, v, prune));
}
for (auto e: current.candidate) {
board next = current.move(e);
next.history.push_back(e);
int delta_depth = current.whom != current.who;
if (depth == cutoff && delta_depth) {
best.val = current.eval(who);
return best;
}
if (next.whom == next.who) { //Still player's turn
next = min_node(next, traverse_log, depth + delta_depth, prune, MIN_NODE, save_log);
} else {
next = max_node(next, traverse_log, depth + delta_depth, prune, MIN_NODE, save_log);
}
if (next.val < v) {
v = next.val;
best = next;
}
if (prune) {
if (best.val <= current.alpha) {
if (save_log) {
traverse_log.push_back(log_string(current, depth, v, prune));
}
return best;
}
current.beta = min(current.beta, best.val);
}
if (save_log) {
traverse_log.push_back(log_string(current, depth, v, prune));
}
//cout << get_node_name(current) << endl;
}
return best;
}
int quiesence(board b, int alpha, int beta, bool hasPass)
{
if (b.inCheck().first || b.inCheck().second)
return minimax(1, b, alpha, beta, 0);
lookupResult res;
bool haveHit = queryTable(b, res);
int bestSoFar;
if (hasPass)
{
alpha = max(b.eval(), alpha);
if (alpha >= beta)
return alpha;
if (haveHit)
{
if (res.type == SCORE_LOWERBOUND)
{
if (res.evaluation >= beta)
return -res.evaluation;
else
alpha = max(alpha, res.evaluation);
}
if (res.type == SCORE_UPPERBOUND)
{
if (res.evaluation <= alpha)
return -alpha;
else
beta = min(beta, res.evaluation);
}
if (res.type == SCORE_EXACT)
return -max(alpha, res.evaluation);
}
bestSoFar = alpha;
}
else
{
if (haveHit)
{
if (res.type == SCORE_LOWERBOUND)
{
if (res.evaluation >= beta)
return -res.evaluation;
else
alpha = max(alpha, res.evaluation);
}
if (res.type == SCORE_UPPERBOUND)
{
if (res.evaluation <= alpha)
return -res.evaluation;
else
beta = min(beta, res.evaluation);
}
if (res.type == SCORE_EXACT)
return -res.evaluation;
}
b.flipToMove();
bestSoFar = quiesence(b, -beta, -alpha, true);
b.flipToMove();
}
vector<move> moves = b.genMoves();
moveOrderer order(b);
sort(moves.begin(), moves.end(), order);
int besti = 0;
for (int i=0; i<moves.size(); i++)
{
if (b.moveGains(moves[i]) < 300)
break;
board temp = b;
temp.executeMove(moves[i]);
int curScore = quiesence(temp, -beta, -max(alpha, bestSoFar), false);
if (curScore > bestSoFar)
{
bestSoFar = curScore;
besti = i;
}
if (bestSoFar >= beta)
break;
}
putTable(b, 0, bestSoFar, moves[besti], alpha, beta);
return -bestSoFar;
}
int minimax(int depth, board b, int alpha, int beta, int movesDone)
{
lookupResult res;
bool haveHit = queryTable(b, res);
if (haveHit && depth <= res.depth)
{
if (res.type == SCORE_LOWERBOUND)
{
if (res.evaluation >= beta)
return -res.evaluation;
else
alpha = max(alpha, res.evaluation);
}
if (res.type == SCORE_UPPERBOUND)
{
if (res.evaluation <= alpha)
return -res.evaluation;
else
beta = min(beta, res.evaluation);
}
if (res.type == SCORE_EXACT)
return -res.evaluation;
}
//if (depth == 0)
// return quiesence(b, alpha, beta, false);
if (depth == 0)
return -b.eval();
if (inHistory(b))
return 0;
moveOrderer order(b);
vector<move> moves = b.genMoves();
sort(moves.begin(), moves.end(), order);
if (moves.size() == 0)
{
if (b.inCheck().first && !b.getToMove())
return MATESCORE(movesDone);
if (b.inCheck().second && b.getToMove())
return MATESCORE(movesDone);
return 0;
}
if (b.getPlyClock() >= 100)
return 0;
int bestSoFar = -MATESCORE_MAX;
if (haveHit)
{
board temp = b;
temp.executeMove(res.bestMove);
pushHistory(temp);
bestSoFar = minimax(depth-1, temp, -beta, -alpha, movesDone+1);
popHistory();
}
int besti = -1;
for (int i=0; i<moves.size() && bestSoFar < beta; i++)
{
if (haveHit && moves[i] == res.bestMove)
continue;
board temp = b;
temp.executeMove(moves[i]);
pushHistory(temp);
int curScore = minimax(depth-1, temp, -beta, -max(alpha, bestSoFar), movesDone+1);
popHistory();
if (curScore > bestSoFar)
{
bestSoFar = curScore;
besti = i;
}
}
if (besti == -1 && haveHit)
putTable(b, depth, bestSoFar, res.bestMove, alpha, beta);
else
putTable(b, depth, bestSoFar, moves[besti], alpha, beta);
return -bestSoFar;
}