OK, it's 40 moves then. I agree that ambiguously worded rules are potential sources of troubles. Can "progress" be defined similarly to chess as irreversible move (move of a checker, a capture, or a promotion)?Ed Trice wrote:The venue for tournament checkers is not nearly what it is in chess. In checkers, they have a vaguely worded "40 move rule" where you simply must "show progress" towards a win, to be adjudicated by a referee if the need arises. The problem would be, in many instances a referee is not on par with the playing strength of those who tend to play out such endings.Kirill Kryukov wrote: Do you have 50 moves rule or something like that in checkers?
I'm not sure if it's easy to strictly define "deliverate exaggeration", or to formalize such rule for computer play. To be practical a rule has to be clearcut. Draw after 40 consecutive reversible moves seems simple enough to be practical. Clearly some such rule is necessary for computer-computer games too, because sometimes it's the only way to interrupt an otherwise infinite game.Ed Trice wrote:In December of 2004, checkers World Champion Alex Moiseyev visited my house, and played against the 7-piece database. It should be noted, this was a win that required 253 plies of perfection. All along the way, one slip would turn it into a draw. Alex was not able to complete the win on the strong side, and when defending the loss, the database found a much shorter route to the win. It is safe to say, such incredibly complex positions are beyond the capabilities of the strongest human.
In my opinion, that rule was designed for human play, and it should remain in the domain of human vs. human competitions. What player would want to play out a 100-move ending in R + B vs. R, for example?Kirill Kryukov wrote:It causes a lot of issues and debates in chess endgame solving, and limits the usefulness of Win-Draw-Loss tables. Also Nalimov tables (the most popular format in chess, distance to win, up to 6 pieces currently) are suffering from not accomodating this rule.
In computer vs. computer tournaments, I say wave the rule and let the programs play it out. Maybe a special set of rules would make sense.
1) If a program announces mate at any point before the 50 move rule would stop the game, the counter resets.
2) If the announcement was "Mate in X" and X + 1 moves elapse, the defending side is awarded the draw.
3) If "X" is ridiculously large and deemed a deliberate exaggeration to circumvent the 50-move rule, the declaring program is given a forfeited loss.
That should make the computer-computer endgames more interesting, and the tablebase generator effort would become more worthwhile.
My bigger problem with ignoring the 50 moves (or 40 moves) rule in endgame tablebases is that it increases the fragmentation of the game ecosystem. Many human players use tablebases to analyze actual tournament games. Now suddenly they find themselves in a situation where supposedly "perfect" endgame knowledge is not applicable to the very same game, because it's not for exactly same game they play in tournaments. A position may be a tablebase win, but the winning line contains a longer-than-50-moves series of reversible moves. Then often it is (currently) impossible to know if the position can really be won or not under tournament rules.
Same for computer tournaments. All computer chess tournaments (that I am aware of) are employing the 50 moves rule. The Elo advantage of considering 50 moves rule in the tablebase is probably unmeasurable (much smaller than the really tiny Elo gain from using tablebases at all). Although things may change slightly when 7-pieces tablebases will become practical in chess.
In checkers the fragmentation is already high (with half a dozen realy popular checkers variants). Adding with / without 40 moves rule will again double the number of variants.
Although I agree that an unbounded database has some more methematical beauty.
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