Author: Andreas Stabel
Date: 06:39:34 04/05/00
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On April 05, 2000 at 00:57:48, Tom Kerrigan wrote: >This is just a semantic argument. What you call stuff depends on how you look at >it. > >1) If you think a chess program searches the chess game tree, then the tree's >branching factor will be 38, although only a tiny fraction of that tree is >actually visited. > >2) If you consider the chess program's search tree separate from the chess game >tree, then the branching factor is 3 (or whatever). > >I think it's pretty shortsighted to delcare one viewpoint correct and the other >incorrect. It just depends on who you ask. But I think we both agree that (2) is >more common. Might as well use it. > >-Tom Perhaps you missed it, but here is some statistics I have from parsing Dann Corbits game collection. I posted it in this thread earlier. Read the five files A.PGN, B.PGN, C.PGN, D.PGN and E.PGN. The files had a total of 25458158 lines and 945950820 bytes giving an average of 37 bytes per line. Read a total of 1496327 games with 112004996 moves including variations, giving an average of 8.45 bytes per move. There were 6605 variations (left parentesises) containing 63879 moves. Excluding the variations there were 111941117 moves giving rise to 113437444 positions, including the start position, with a total of 3545011178 legal moves giving an average of 31.25 legal moves in an average position. The 111941117 moves was: Pawn moves : (27.15%) 30386622 Knight moves : (18.23%) 20403265 Bishop moves : (15.86%) 17748466 Rook moves : (18.24%) 20418343 (including castlings) Queen moves : (11.97%) 13403989 King moves : (10.89%) 12190285 (including castlings) Short castlings: ( 2.09%) 2337283 Long castlings : ( 0.24%) 272570 Checking moves : ( 4.98%) 5571618 (including mating moves) Mating moves : ( 0.04%) 48748 Stalemating moves : ( 0.001%) 986 Hit moves : (20.65%) 23116992 (including en passant moves) En passant moves : ( 0.08%) 86830 Pawn two moves : ( 7.59%) 8494513 Promotion to queen : ( 0.07%) 82298 Promotion to rook : ( 0.0008%) 839 Promotion to bishop: ( 0.0003%) 281 Promotion to knight: ( 0.001%) 1519 Results of the 1496327 games were: White won: (38.70%) 579064 Drawn : (29.89%) 447291 Black won: (29.11%) 435569 Unknown : ( 2.30%) 34403 Decided games: White mated : ( 1.42%) 21259 White stalemated: ( 0.03%) 479 Black mated : ( 1.84%) 27489 Black stalemated: ( 0.03%) 507 So by this evidence the branching factor could be said to be 31. Perhaps som food for thought :) Regards Andreas Stabel
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