Author: Robert Hyatt
Date: 11:40:13 11/16/00
Go up one level in this thread
On November 15, 2000 at 05:06:44, Jason Williamson wrote: >On November 15, 2000 at 04:14:55, Bruce Moreland wrote: > >>On November 15, 2000 at 02:04:12, Jason Williamson wrote: >> >>>In the 2nd game I ran with xboard engines under CM8000 a serious >>>misinterpratation of the 50 move rule was uncovered. >>> >>>The ending in particular was a drawn Rook and Bishop verus Bishop ending. After >>>the 50th move with the move of a pawn or capture of a piece by white, black >>>(Zchess 2.22) claimed the draw and according to its log quit. >>> >>>The problem is, the CM8000 gui doesn't know how to do the 50 move rule. What it >>>seems to think is that the draw is after the 50th move SET, ie white AND black, >>>which is clearly wrong. To test this theory out, I moved knights and rooks >>>around from the starting position for 50 moves. Since no pawn was moved, nor >>>anything was captured, the 50 move that this happens would be white 50 (0+50=50) >>>but the GUI only claims the draw after the black 50th move. >>> >>>Anyway, this would basicly break any and all winboard engines that are coded >>>correctly and this bug would be a frequent vistor to engine vs engine matches. >>> >>>So, how long until the patch. :) >>> >>>Cheers. >>> >>>JW >> >>The rule is that 50 moves must have been made *by each side*, so the CM gui is >>correct. >> >>Imagine if we had a one-move rule instead of a fifty-move rule. White could not >>claim that 1. Nf3 is drawn by this rule, but after 1. Nf3, black could claim >>that 1. ... Nf6 does in fact draw by this rule. >> >>If 1. e4, black cannot claim that 1. ... Nf6 forces a draw by this rule, but >>after 1. e4 Nf6, white can claim that 2. Nc3 forces a draw. >> >>bruce > >Hmm, it seems you are correct. :) (Looked up the rule at the CFC homepage to >double check). The problem with this situation is this: White's 71 move was a >capture. Both Crafty and ZChess's logs state draw on move white 121. Thus, it >appears that both Crafty and ZChess interupt this rule wrong. As you pointed >out, black must play 50 moves as well, and that means black must play its 121st >move. > >Interesting. > >JW Crafty doesn't do it wrong, to the best of my knowledge. It requires that exactly 100 plies be played _after_ a non-reversible move. Whomever makes the 100th ply move _may_ claim a draw, or he may choose to play on. Then the other side can immediately claim the draw, play on, or even push a pawn to shut the door on the draw claim. IE this isn't a forced draw at all, although in a zero-sum game, if one side chooses to avoid the draw, the other side should choose to claim it. If you have an example where Crafty doesn't do this right, let me know, but at present I don't see how it can fail. The rule says 50 moves by both sides _after_ a pawn-push/capture. The scenario you tested is fine to test with. Crafty should claim a draw if you play 49 knight moves for it, 49 knight moves for yourself, then play one more move for you and let crafty search in a position with no possible captures or pawn pushes. If you give it a chance, it should instantly push a pawn or capture something unless it thinks the score is -.
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