Author: Uri Blass
Date: 16:11:11 12/27/04
Go up one level in this thread
On December 27, 2004 at 18:08:12, José Carlos wrote: >On December 27, 2004 at 17:05:26, Steve Maughan wrote: > >>José, >> >>>> Hi Steve, >>>> Why "and (not_in_check)"? I mean, if you're going to reduce because you're >>>> almost sure you're gonna fail low, being in check is not likely to >>>> suddenly make you fail high... Am I missing something? >> >>As Uri said, if you're in check then it's not really a quiet position. IMO the >>History Pruning heuristic can be useful for pruning the "Reh1" type moves. >> >>Steve > > Thanks Uri and Steve, now I see your point. But still, I'm not sure why it >shouldn't work (note that I don't have history heuristic implemented, so I can't >test nor speak from experience). > Let's have a look at the pseudocode again: > > make_move; > if (moves_made_already > 3) > and (not_in_check) > and (opponent_not_in_check) > and (move_does_not_attack_opponents_king) > and (history_value * 128 < best_history_value_from_this_node) > then > prune or reduce_depth; > > I guess (not_in_check) means _before_ making the move. If we make the move, >now our king is not in check. We're trying to guess if the position after making >the move is ok to reduce or prune, this is, it is a bad position for us. If I >was in check, move out of check and still my position sucks, and it is my >opponent's turn... I'm likely to fail low, right? > I undertand that the main idea of this heuristic is to prune moves like Reh1, >as Steve mentioned, but pruning a move where I get out of check in a lost >position also makes sense. > Could any of you try a quick test by removing that condition? > > José C. Maybe an example will help to explain it better I remember that I found that pruning move based on history when the king is in check may cause problems here because white can play e7 and promote the pawn but black has some checks before the promotion. You can say that the reason is a promotion threat and I can not prune when there is a promotion threat but there may be other dangerous threats that the opponent prevenet temproraly by checks and I do not detect all the dangerous threats. [D]8/p3q1kp/1p2Pnp1/3pQ3/2pP4/1nP3N1/1B4PP/6K1 w - - bm Ba3 Uri
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