Author: Christophe Theron
Date: 14:36:09 01/30/98
Go up one level in this thread
Hi everybody (because it looks like there are people watching this game,
not only Ed and I)!
Tiger plays:
18. Bxe6
(...fxe6 19. Nd6 Ke7 20. Rd2...
time=10.38, ply=11, score=+1.40)
[Event "Correspondance game"]
[Site "Internet"]
[Date "1998.01.01"]
[Round "?"]
[White "Chess Tiger K5 100Mhz 256Kb hash 1h/game"]
[Black "Sargon III Apple 2e 24h+/move"]
[Result "*"]
1. e4 c5 2. Nc3 b6 3. Nf3 Bb7 4. d4 cxd4 5. Nxd4 e5 6. Nf5 Nf6
7. Bg5 h6 8. Bxf6 Qxf6 9. Nb5 Kd8 10. Nfd6 Bc6 11. Bc4 Bxb5
12. Nxb5 Bb4+ 13. c3 Bc5 14. 0-0 a6 15. Qd5 Nc6 16. Rad1 Qe6
17. Qxc5 bxc5 18. Bxe6 *
>Interesting scores. Sargon =-.64 (good for white)... Tiger = +1.6.
>Crafty is right in the middle, and says +.9... :)
So you where watching too, Bob?
Tiger has very high weights. I think some are really too high. They come
from the previous version, which was not computing deep enough. So I had
to put really high weights to make Tiger understand that some weaknesses
are very close to losing material.
Sargon's weak pawn on the open D file is a good example. But this is not
the only part of this "overevaluation".
There was a time when Tiger had so high weights that it would never take
a weak pawn. Instead, it kept on puttin pressure on it. Because the
pressure was valued higher than a pawn!
Another example (and I almost got crazy on this one): Tiger was able to
say, under some conditions, that a passed pawn could never be stopped.
So I gave it a very high score. And sometimes CT pushed the pawn up to
the 7th rank, then never made the promotion. It kept moving its king
around instead. It took me some time to realize that the bonus for the
passed pawn was higer than the value of a queen. So the position where
the pawn was ready to promote had a higher value than the position after
the promotion!
I suppose many chess programmers have already fallen in this trap.
Things were in fact more complicated, because I wanted Tiger to handle
some positions where you have KQP against KP, the latest P being on its
7th rank. In this case, sacrifice your queen against the pawn, and
promote your own pawn to win. To do this, I valued my only pawn higher
than a queen, only if the opponent had only its K. But it didn't work...
Christophe
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