Author: Robert Hyatt
Date: 18:54:23 08/03/99
Go up one level in this thread
On August 03, 1999 at 15:34:54, Ricardo Gibert wrote: >On August 03, 1999 at 14:28:04, Robert Hyatt wrote: > >>On August 03, 1999 at 10:28:25, Ricardo Gibert wrote: >> >>>On August 03, 1999 at 09:00:33, Robert Hyatt wrote: >>> >>>>On August 03, 1999 at 04:45:07, Ricardo Gibert wrote: >>>> >>>>>On August 03, 1999 at 04:32:27, Bruce Moreland wrote: >>>>> >>>>>> >>>>>>On August 02, 1999 at 22:47:14, Ricardo Gibert wrote: >>>>>> >>>>>> >>>>>>>Your post is a little ambiguous. Are you saying Nalimov EGTB is a shortest mate >>>>>>>EGTB for all the 5 man endings? How would the tables be generated? >>>>>>> >>>>>>>I would be surprised if all the endings covered by the Nalimov EGTB are of the >>>>>>>shortest mate variety. I would also be disappointed for the reason indicated. >>>>>>>Some endings (other than KQKR which a computer program can win in about 34 >>>>>>>moves) would be "impossible" to win using such a TB due to the 50 move rule. >>>>>> >>>>>>I would be suprised if the Nalimov tables are *not* distance to mate. The only >>>>>>publicly available distance to conversion tables that I know of are the Thompson >>>>>>tables. >>>>> >>>>>Shortest mate EGTB also has the defect of possibly concluding that an ending is >>>>>drawn due to the 50 move when it is actually winning. By the way, I think this >>>>>issue can be cleared up by noting that "distance to mate" is not necessarily the >>>>>same as "shortest mate". >>>> >>>> >>>> >>>>first, 50 move draw is _not_ included. How could it be? Because you have >>>>_no_ idea what position you will enter the database at... >>>> >>>>and distance to mate _is_ "shortest distance to mate" absolutely... >>>> >>>Then this means the EGTB will prefer a mate in 51 without pawns moves or >>>captures to a mate in 52 with a pawn move or capture before the 50 move rule >>>kicks in. It will draw winning positions. Undesirable and unnecessary. >>>Fortunately rare. >>>> >> >> >>yes... but this is a problem no matter what. Because the tablebase is just >>a file that is indexed by piece location, and it provides mated-in-N, draw, or >>mate-in-N. It has _no_ idea about prior positions and what might have >>transpired before reaching this position. It can't even tell if this position >>is a successor of another position in this file, or if it was reached via a >>capture with a zero 50-move counter. > >prior positions are irrelevant. > you are wrong here. I play move A, then move B (which unmakes move A), then move A again, then move B again, and now I probe the table, and it says if you play move X you win the rook in 4 moves. Unfortunately, a couple of moves before you win the rook, you play move A again and the position is repeated and the game ends as a draw. If you don't have state information in the database, there is _no_ way to probe it and ask about such things.. because it says you can capture a piece in 29 moves, but how many _prior_ positions of yours do you repeat before doing so? This is an old discussion. There are _many_ problems here... >> >>deep mates are going to be a problem in 6 piece files, no doubt about it. It >>would be interesting to see if there are already violations of this in the 5 >>piece files... >> >> >> >>>> >>>> >>>>>> >>>>>>And yes, the tables do suffer from the possible problem that you mentioned, >>>>>>although this should be extremely rare in practice. >>>>>> >>>>>>bruce
This page took 0.01 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.