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Subject: Don't try this at home

Author: Mark Longridge

Date: 23:51:21 08/05/01


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



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