Author: Miguel A. Ballicora
Date: 19:59:39 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. That'll be interesting, please post what you find, it will be very informative. >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. KRN vs KR, Kasparov beat J Polgar, even though is way much simpler. > If I can beat 'em with a KRB vs KR ending, then I can almost certainly >beat them with a KRBP vs KRP ending. That is true. Regards, Miguel
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