Author: Robert Hyatt
Date: 20:39:33 10/30/01
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On October 30, 2001 at 16:12:20, Miguel A. Ballicora wrote: >On October 30, 2001 at 15:54:06, Robert Hyatt wrote: > >>The point here is that KRBP vs KRPP might seem to be the same as a KRB vs KRP >>ending. The KRB has no chance of winning in a real game. There may be a >>contrived position where the KRB side wins, but I haven't seen any in real >>games yet myself. I don't want _my_ program to trade from a possiblly >>winnable KRBP vs KRPP, to a absolutely unwinnable KRB vs KRP ending, if I can >>help it. > >This is true against a computer with EGTB's, against humans it is not exactly >unwinnable. Particularly with "game in x" time control where it is closer to a >win than a draw. Practical chances are very high, it is a tough endgame to >defend unless you have plenty of time and know the theory. > >Regards, >miguel It isn't that hard for a computer. I ran a few such tests a few years ago. The first was KQ vs KR, with crafty playing KQ with no tablebases, against Crafty with KR using tablebases. Crafty with KQ won _every_ time within 50 moves, with no special heuristics at all other than "drive the king to the edge and then the corner." In fact, on a P6/200, it could win every time given only a couple of seconds. When Steven Edwards made me the KRP vs KR tablebase, along with the promotion cases, I tried this again after watching Crafty play a KRB vs KR ending and being unable to win it (I had never noticed that this is generally drawn). I tried tablebase KRB vs no-tablebase KR and the no-tablebase side had no problems in drawing every game. With very shallow searches. I _have_ seen programs lose drawn endings. Crafty and WchessX once played a KR vs KN where Crafty had the KR (no tablebases back then) and it still won the game. However, I would not expect to repeat that against _any_ human or computer I would really expect to have to play. Maybe against a 1500 it might win. But not against a strong player. And I am generally thinking of IM/GM players as the competition I play against, which simplifies things a bit.
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