Author: Robert Hyatt
Date: 20:06:25 01/23/02
Go up one level in this thread
On January 23, 2002 at 22:56:07, Russell Reagan wrote: >I'd like to know two things for each of the values. I'd like to know the >theoretical maximum value, and a practical maximum value for use in a chess >program. > >Here's what I'd like to know: > >Maximum number of moves a chess game can last, and a good value for the maximum >size of the move history stack. The game is infinite. If you read the rules of chess, the 50 move rule is not absolute, either side _may_ claim a draw after 50 non-capture/non-pawn moves occur, but they are not _forced_ to do so. If you make the 50 move rule forced, then the game is limited to rougly 5050 moves, assuming you make 49 non-capture/non-pawn moves, then move a pawn or capture something, then continue the process until there are only two kings left. > >Maximum number of legal moves in a chess position, and a good maximum value for >the legal moves array. no one has beat 219 yet. But that doesn't mean it doesn't exist. I see no reason to have _any_ maximum, just use an appropriate data structure instead and if someone finds that oddball position with 500 moves you won't have a problem... > >I can't think of anymore maximum values that would be good to know, but I was >just thinking about how horrible it would be to set the size of the move history >stack to some value and then in some crazy game that is clearly drawn have my >opponent draw it out hundreds of moves more by piddling around and making a pawn >move every 40-50 moves. Not likely, but I'm sure stranger things have happened. >Same with the legal moves maximum. I'd hate to miss a move because I didn't >create a large enough legal move array. > >I recall someone a long time ago giving a value for maximum number of moves to >be around 5,400, and I'm guessing that maximum number of legal moves is around >80-100+. > >If all else fails, the legal move array could be 269, since that would account >for 9 queens, 2 rooks, 2 bishops, 2 knights, and 1 king all with maximum number >of legal moves. All of those pieces obviously cannot all have the maximum number >of legal moves if they're all on the board, so 269 would be a safe maximum. > >As for the maximum number of legal moves, 6300 should cover it since 16 pawns at >a maximum of 6 moves each, plus 30 captures, totals 126. So you could have 126 >blocks of 50 moves. And I guess that would really be blocks of 49 moves, as 50 >would be a draw, totallying 6174 total moves. > >Even at 6 bytes per move, that's only ~50K of memory. > >If anyone knows these exact values off hand, or cares to take the time to >compute them accurately, I'd love to know them. If not I'll just shoot high and >waste a few bytes :) > >Russell
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