Author: Bruce Moreland
Date: 22:35:31 08/06/99
Go up one level in this thread
On August 06, 1999 at 20:01:16, Robert Hyatt wrote: >On August 06, 1999 at 17:56:35, KarinsDad wrote: > >>On August 06, 1999 at 13:59:10, Robert Hyatt wrote: >> >>[snip] >>> >>>It is a _long_ way from easy. The path has to go at least 100 plies beyond the >>>first capture/pawn push to make sure you won't run afoul of the 50 move rule >>>down that path. And to search that path is just a perfectly normal search, >>>which translates into _impossible_ to do... The databases don't contain trees, >>>they just contain a score for each possible position that can be reached... >>> >>>and I don't see any way to fold in the 50-move rule because of this... hence the >>>other thread and DTC scores... And even that won't work if the computer has to >>>'take over' a position played by a human, because then you can't assume optimal >>>play since reaching a database win, and at that point, the 50 move rule is >>>death to any sort of probe... >>> >> >>I now understand the difficulties involved (the "take over" case is probably not >>even worth discussing). >> >>My recommendation: punt. > >I agree... but note that many are not going to like this, perhaps yourself >included, when you want to analyze some endgame you played to see what will >happen after the game is resumed... But I don't see a real solution to this >problem... > > > >> >>Chances are, even if you are playing another program with TBs, you will rarely >>find move by rep situations or violations of the 50 move rule once you get to >>the TBs. So, if you get to the TBs, it will either be a lose, a draw, or a win >>by default and the chances of it changing from a win to a draw (or a loss to a >>draw) due to either of these two rules should be extremely slim. > >that's debatable... since the losing side also has TBs, it will certainly >put off the loss as long as possible, which might cause problems (ie in Eugene's >kbn vs kn mate in 100+ position). And if the DTC value is ever added, I'd >certainly be checking it when I was losing, to always take a move with DTC+ >current-50-move-counter > 50, to ensure a draw in a technically won ending. :) > > > > > >> >>Note: The move by rep problem can be minimized (but not eliminated) by using a >>little AI on choice of moves out of the tablebase. For example, if the white >>king has only been on f4 since the last capture or push (the reset for 50 move >>and for move by rep), then you could search the TB for moves that still mate, >>but start moving the white king away from f4 (or somesuch). >> >>Do you have statistics for Crafty on percentage of times (against computer >>opponents with TBs only) that a win (or a loss) was changed to a draw due to >>this (either for Crafty or for it's opponent)? >> >>KarinsDad :) > > > > >I don't believe it has ever happened, at least not that I have seen. That KP vs KNN mate in 106 or whatever may have been a case of this. If you guys are talking about how to avoid 50-move rule in a DTM database, the most obvious way to do this is to use a DTC database (not Thompson's, which doesn't count a pawn move as a conversion, I believe) to turn every won position with a DTC of more than 50 into a drawn position in the DTM database. bruce
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