   NegaScout & TT
  Hi,I use NegaScout along with Transposition Table but I don't save results obtained via calls with zero-window: alpha, alpha+1. In fact I don't use TT in zero-window search at all. I'm not sure but I think saving these results may lead to mistakes. Can I somehow make use of zero-window search result in context of transposition table?   
  You should definitely store and use the results of zero-window searches. If you also store a flag indicating whether the stored result is an exact score, a lower bound or an upper bound, this shouldn't lead to any mistakes.Some pseudo code:int NegaScout(Board &b, int depth, int alpha, int beta) {  if (depth<=0)    return static_eval(b, depth);    HashEntry *he = hash_search(b);  if (he != 0) {    if (he->depth >= depth) { // Don't use the score otherwise switch (he->flag) { case LOWER_BOUND:   alpha = max(alpha, he->score);   break; case UPPER_BOUND:   beta = min(beta, he->score);   break; case EXACT_SCORE:   return he->score; } if (alpha>=beta)   return alpha;    }  }    // The loop goes here. Make sure to search the move stored in the hash table  // first, even if (he->depth < depth). Also, break out of the loop in case of  // a beta cut-off, instead of simply returning the score. This will give you  // an opportunity to update the hash table, the history-heuristic table, etc.    HashFlag flag = (best_score <= alpha) ? LOWER_BOUND : (best_score >= beta) ? UPPER_BOUND : EXACT_SCORE;    store_hash(b, depth, score, flag, best_move);    return best_score;};  Yes, I store value type indicator. I wasn't only sure about zero-window. Thanks!   