Author: Uri Blass
Date: 13:01:40 10/31/01
Go up one level in this thread
On October 31, 2001 at 11:13:09, Robert Hyatt wrote: >On October 31, 2001 at 09:56:02, Miguel A. Ballicora wrote: > >>On October 30, 2001 at 23:39:33, Robert Hyatt wrote: >> >>>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. >> >>The last point is what you might want to reconsider. Maybe I was not clear >>before, this endgame is tough for IM and GMs that do not know the theory (and >>there are many). Tough even at slow time control. If they do not know the >>theory, and they play blitz, Crafty will score >95%. If they know the theory and >>it is blitz crafty will still score a lot of points since is very easy to make a >>mistake on the crucial positions. That's all you need. >> >>I personally was able to hold this position against an IM many years ago with 3 >>minutes on my clock only because I knew the theory perfectly and I had it >>_fresh_ on my mind. He was very dissapointed not to bring the point home. >>If you are a IM/GM and you knew the theory but haven't touched it in a long time >>you might lose precious time before you remember. Particularly at speed chess! >> >>If you do not believe me, I will try to find a Nunn's quote about this. >> >>Miguel > > >I will try to find a few games with this position in Crafty's huge PGN archive. >I know it has played two GMs and reached this position and they drew it with >no difficulty. I'm sure some can't, but the issue is that I do _not_ want to >reach KRB vs KR or KRN vs KR against _anybody_ because it _should_ be >drawn. If I can beat 'em with a KRB vs KR ending, then I can almost certainly >beat them with a KRBP vs KRP ending. 1)The problem is not this case. The problem is that Crafty may trade a bishop for a pawn and get KR vs KR and not KRB vs KRP 2)if Crafty evaluate everything in KRB vs KP as a constant evaluation of 0.00 or even 0.01 for the side with more material then it is not going to try to improve it's position and it may help humans to draw KRP vs KRB with no difficulty 3)Crafty can avoid trading pawns with evaluation that is not a constant evaluation and this subject was discussed here in previous posts. Uri
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