Sean Evans wrote:Closed positions are quite common in chess and should be reflected in a chess programs evaluation, ex. Knights are better than Bishops in closed positions!hyatt wrote:biscuit1953 wrote:I have no idea where I got this position but found it in some old files I was getting rid of. It's amazing that of all the engines I tested all except Critter think that White's position is hopeless while obviously it is a dead draw.
6kr/5b1p/2p3pP/rpPp1pP1/pP1PpP2/P3P3/1K6/8 w - -
There are versions of Crafty that find this instantly. By evaluation. The problem is, how often have you seen such a position? How much will recognizing that improve a program? And most importantly, how much time does that waste in the evaluation and what is the cost in the positions where such locked pawns don't occur? Answer to the second question. It won't improve the Elo at all. The answer to the third question is "it costs quite a few Elo because it slows the NPS down and reduces the depth slightly." If you look at crafty 19.10 and a few versions after that, there is specific code (not written by myself, contributed by someone else. If you compile with -DDETECT_DRAWS it should find that instantly. Unfortunately the cost was too high and it was removed in later versions...
Closed positions where one can take a rook and lose are NOT very common in chess. Most programs evaluate closed positions to some extent, just not to the extent required to not take the rook or whatever...