Author: Ricardo Gibert
Date: 20:13:13 08/03/99
Go up one level in this thread
On August 03, 1999 at 21:54:23, Robert Hyatt wrote: >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. The EGTBs hits should be "part" of the eval. A tool. You catch 3 fold reps the same way you always do. For example, distance to mate also would have this "problem". What difference does it make if you find mate or win of a rook? Besides, after you play A the 1st time, you probe and find move X to win the rook. No 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.