Author: Robert Hyatt
Date: 20:01:03 08/06/01
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On August 06, 2001 at 02:51:21, Mark Longridge wrote: >I recently updated my book for crafty by including all the games it's ever >played, including some pretty bad ones. > >I started with all.pgn and inside crafty I typed: > >book create all.pgn 80 1 55 > >Now, my understanding was that the last argument meant "prune everything that >did not win 55% of the time. Imagine my surprise when my computer as white >played: > >1. e4 c6 2. Ke2 d5 3. Kd3 dxe4+ 4. Kxe4 > >What the???? Fortunately it was an unrated game, which was actually >an aborted game which never got passed move 5, _but_ when crafty >does it's result pruning, there is still the case (like this game) >where there was 1 game played, but no result. The no result games don't >get pruned, so even if it's the worst chess opening there is, it's >still included in the book.bin > >A bit careless on my part, but I was still surprised because if this >line has 0 wins, it's win percentage is 0% and therefore should be >pruned. > >Mark the win percentage means this: If you say "50" then there must be at least 50% as many wins as there are losses. IE if there are 10 losses, there must be at least 5 wins to meet that requirement. If there is only one game, with no result tag, then there are zero losses, which means zero wins also meets it. use "minplay" to exclude openings not played at least N times where N is 5 to 10. That will eliminate this stuff.
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