Author: Robert Hyatt
Date: 18:47:04 08/03/99
Go up one level in this thread
On August 03, 1999 at 15:33:10, Ricardo Gibert wrote: >On August 03, 1999 at 14:25:21, Robert Hyatt wrote: > >>On August 03, 1999 at 10:39:37, Ricardo Gibert wrote: >> >>>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. >> >> >>sure... but I then "don't get it". IE if the human can use the tablebases, he >>will mate optimally. If he can't, he has to either do it by himself or not at >>all. I don't quite see how the human could play for a while, then turn it over >>to a tablebase (which could certainly screw up there as optimal might be a >>mate in 20, while 40 moves have already been played and 20 more would take the >>game past move 50. > >You "don't get it", because you have overlooked the word "adjourned". > >I will give a more specific example: HUMAN plays an ending where he ADJOURNS. He >must mate OR make pawn move that preserves win OR capture that preserves win >within say 6 moves to avoid the 50 move rule. In his ADJOURNMENT ANALYSIS, if he >uses a SHORTEST MATE database, he may wrongly conclude he can't do it. > >1. Instead of > distance to: mate > >2. Better is single number representing > distance to: mate OR win preseving capture OR win preserving pawn move > (whichever comes soonest) > >The 2nd way you ALWAYS win a winnable position. I find it hard to believe >Nalimov did his EGTB the way you assert (The 1st way). There is nothing I can >think of that would make the 2nd way listed above significant more difficult to >do. There is no good reason, I can think of, for using the 1st way in preference >to the 2nd one. > >I hope this is more clear, otherwise, I give up. > Now I understand the context. But remember, DTM databases are built based on _perfect_ play. And they only store _positions_ and distance to mate, not path information. So I see no way possible to accomplish what you are asking for, because that information is _not_ present. >> >>And this problem already exists. I believe the deepest mate in the 5 man >>files is 127, although Eugene can correct me here. And perhaps the deepest >>mates still have a capture or pawn push in them to defeat the 50 move rule. >> >>six piece files will be something else altogether, of course... >> >> >>>> >>>>> >>>>>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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