Author: Ricardo Gibert
Date: 07:39:37 08/03/99
Go up one level in this thread
On August 03, 1999 at 08:58:35, Robert Hyatt wrote: >On August 02, 1999 at 22:47:14, Ricardo Gibert wrote: > >>On August 02, 1999 at 20:49:56, Dann Corbit wrote: >> >>>On August 02, 1999 at 20:06:07, Ricardo Gibert wrote: >>> >>>>On August 02, 1999 at 18:15:27, Jeff Anderson wrote: >>>> >>>>>Could someone with access to the KQ v kr endgame tablebase tell me how many >>>>>moves before Black mates in this position? >>>> >>>>I believe the tablebases are not optimized for finding the shortest mate. For >>>>instance, in this case, it finds the shortest route to mate OR win the rook. >>>>After winning the rook, it then finds the shortest mate from there. So it is >>>>possible the "best" play generated by the table base is not the shortest mate. >>>>It is also possible for a tablebase, organized differently, can give a solution >>>>of a different length than another tablebase, though I would not expect that >>>>here. >>>> >>>>So "perfection" is not guaranteed, but it does have the virtue of being optimal >>>>in the light of the 50 move rule. In other words, it is possible that a position >>>>is winnable without exceeding the 50 move rule, but the "shortest mate" would >>>>exceed the 50 move rule. Of course, in that case it would not really be the >>>>"shortest mate." I would be interested in seeing an example position of this if >>>>someone has it. >>>The Nalimov tablebase files have distance to mate. But as a confirmation, here >>>is the output of Chest: >> >>With Nalimov, it is possible that is always the case for KQKR as memory >>requirements are not a factor to generate a shortest mate EGTB for this ending, >>but I've already given a reason why this is undesirable. >> >>The reason can manifest itself in the case where you have adjourned in an KQKR >>ending (human vs human) and have only x numbers of moves to avoid the 50 move >>rule. Using a tablebase for your adjournment analysis that gives "shortest mate" >>instead of "shortest win of rook or mate" could be a problem. > > >this can't possibly happen unless someone has a bug. KQ vs KR is _never_ >won in more than 50 moves. So at the point where the program reached this >ending, it plays it optimally. Your case could not possibly happen. In >other endings, this is a possible problem, but only if it is mate in > 50 >from the starting position where the ending is reached. > It appears you overlooked the phrase "human vs human". We both overlooked it can also happen in Human vs computer where the human is the superior side. > >> >>Objectively speaking, it is never wrong to win the rook instead. Subjectively >>speaking, your opponent is bound to resign after losing the rook anyway. >>Shortest win can be faster than the shortest mate in that case. >> >>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? > >this is correct. You start by enumerating all possible 5 man positions, and >marking the ones that are "mate" and then working backward. Takes a lot of >time to build, not time to probe. > > > > >> >>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. >> > >Eugene does use distance-to-mate in all files... > > >>By the way, back in the days when a 20mhz 386 was a high end machine, I helped a >>friend of mine learn how to play KQKR perfectly using the Thompson EGTB. I >>myself learned how to do it within the 50 move rule. Not so easy against a >>computer even though I am a master. Miles & Browne are 2 well known players that >>have been embarassed. I don't think I can do it today. >> >>My friend showed up for a big tournament in Canada (St. Johns?) where a guy was >>showing off his program that could play KQKR. I guess he got a kick out of >>embarassing all the titled players there. My friend consistently won the ending >>in the "optimal" number of moves. The guy couldn't believe it. >> > > >this ending is remarkably easy to win, even without databases. I ran several >tests last year and was surprised that even at a couple of seconds per move, >Crafty could win using no tablebases, against a version of itself that did. > > > >>>Reading job: >>>W: Kg2 Rf2 (2) >>>B: Kg4 Qa2 (2) >>>FEN: 8/8/8/8/6k1/8/q4RK1/8 b - - >>>analysing (mate in 14 moves): >>>No solution in 14 moves. >>>refu 1: Qa8+ Kf1 [ 13-] >>>solu 1: Rf3 [ 4+] >>>solu 2: Kh2 [ 12+] >>>solu 3: Kg1 [ 10+] >>>refu 2: Qd5+ Kf1 [ 13-] >>>solu 4: Rf3 [ 4+] >>>solu 5: Kg1 [ 4+] >>>solu 6: Kh2 [ 13+] >>>refu 3: Qa3 Kg1 [ 13-] >>>solu 7: Rd2 [ 5+] >>>solu 8: Rc2 [ 11+] >>>solu 9: Rf6 [ 12+] >>>solu 10: Rf4+ [ 4+] >>>solu 11: Rf7 [ 13+] >>>solu 12: Rf1 [ 8+] >>>solu 13: Kh2 [ 5+] >>>solu 14: Rf5 [ 6+] >>>solu 15: Rf3 [ 4+] >>>solu 16: Rf8 [ 4+] >>>solu 17: Re2 [ 4+] >>>refu 4: Qa4 Rd2 [ 13-] >>>solu 18: Rf6 [ 11+] >>>solu 19: Rf7 [ 12+] >>>solu 20: Rf8 [ 13+] >>>refu 5: Qa5 Re2 [ 13-] >>>solu 21: Rf4+ [ 4+] >>>solu 22: Rc2 [ 12+] >>>solu 23: Rf6 [ 11+] >>>solu 24: Rf7 [ 7+] >>>solu 25: Rf1 [ 6+] >>>solu 26: Rf8 [ 13+] >>>solu 27: Rb2 [ 11+] >>>solu 28: Rf3 [ 4+] >>>solu 29: Kh2 [ 12+] >>>solu 30: Rf5 [ 4+] >>>refu 6: Qa6 Rd2 [ 13-] >>>solu 31: Rf4+ [ 4+] >>>solu 32: Re2 [ 3+] >>>refu 7: Qa7 Rc2 [ 13-] >>>solu 33: Rf4+ [ 4+] >>>solu 34: Kg1 [ 3+] >>>refu 8: Qa1 Rf8 [ 13-] >>>solu 35: Rf4+ [ 4+] >>>solu 36: Rf6 [ 4+] >>>solu 37: Rb2 [ 3+] >>>refu 9: Qb3 Kg1 [ 13-] >>>solu 38: Rf4+ [ 4+] >>>solu 39: Rd2 [ 5+] >>>solu 40: Rf6 [ 11+] >>>solu 41: Rf5 [ 5+] >>>solu 42: Ra2 [ 3+] >>>solu 43: Rf8 [ 13+] >>>solu 44: Rf1 [ 6+] >>>solu 45: Kh2 [ 5+] >>>solu 46: Rf3 [ 4+] >>>solu 47: Rf7 [ 4+] >>>solu 48: Re2 [ 4+] >>>refu 10: Qc4 Rd2 [ 13-] >>>solu 49: Rf6 [ 11+] >>>solu 50: Rf4+ [ 3+] >>>solu 51: Rf5 [ 6+] >>>solu 52: Rf3 [ 4+] >>>solu 53: Rf7 [ 4+] >>>solu 54: Rf1 [ 6+] >>>solu 55: Re2 [ 3+] >>>solu 56: Rc2 [ 3+] >>>solu 57: Ra2 [ 3+] >>>solu 58: Rf8 [ 13+] >>>refu 11: Qe6 Rd2 [ 13-] >>>solu 59: Rf4+ [ 4+] >>>refu 12: Qg8 Rd2 [ 13-] >>>solu 60: Rf4+ [ 4+] >>>solu 61: Rf3 [ 4+] >>>refu 13: Qb1 Rf8 [ 13-] >>>solu 62: Rf4+ [ 4+] >>>solu 63: Rf7 [ 12+] >>>solu 64: Rf6 [ 11+] >>>solu 65: Rf5 [ 4+] >>>solu 66: Rc2 [ 3+] >>>solu 67: Ra2 [ 3+] >>>Time (user) = 856.00 sec (ca. 14.3 min)
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