Author: Pekka Karjalainen
Date: 04:49:15 07/20/04
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On July 20, 2004 at 07:30:11, Dan Honeycutt wrote: >On July 20, 2004 at 07:02:43, David Rasmussen wrote: > >>Does anybody know a source for the claims that >> >>1) the longest possible chess game is some 6000+ moves. >> >>2) the average branching factor in chess is 35 (og 37 og 40 or...) >> >>/David > >The first is easy to deduce - every 50 moves a pawn must advance or a piece must >be captured: > >(16 pawns * 6 squares + 30 pieces) * 50 = 6,300 moves. > >Dan H. This is only an upper bound, since the pawns block each other. They can't get to promotion squares without some sort of captures. If the blocking pawns are captured their moves don't figure in the total, or if the pawns capture pieces, they also advance at the same time. Off the top of my head I figure that eight combined captures and advances are enough for one side to dodge around the other. That would lose 400 moves from the total. Then there is the issue of black's and white's captures happening on plies of different parity. Does that lose some moves too? Then you'd have to decide whether the last 50 moves with nothing but the kings on board count or not, by rules. I guess they don't. No matter how you look at it, it's a theoretical figure and requires cooperative play by both sides. Pekka
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