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AW: [gnugo-devel] a patch from a newbie :)

From: Portela Fernand
Subject: AW: [gnugo-devel] a patch from a newbie :)
Date: Tue, 10 Sep 2002 11:27:53 +0200

Dan wrote:

> Could you explain the meaning of HALFWIN and HALFLOSS and the
> general intent of the patch?

The meanings would be something like :

* HALFWIN : attack failed ( dragon not killed ), but something
            "substantial" can be captured.
* HALFLOSS : defense successfull ( dragon alive ), but something
             "substantial" has to be sacrificed.

I thought of PLUS and MINUS, but found them too general...

> I looked at blunder:12. Arend: is there any relevance of the recent
> patch arend_3_7.2 to this problem? It is a case where part of the
> dragon can be discarded so the dragon cannot be owl attacked. Since
> the number of liberties is small, I would think D4 should be a
> tactical attack if fourlib_depth is sufficient.

blunder:12 is the typical case where the atari_atari code fails,
mainly because after W D4 B D3, the only one attacked string has
suddenly 5 liberties (I guess, this is the "reason" of the C6 liberty 
in the problem). At the same time, the OWL code "sees" the correct
sequence, but fails to consider it a WIN, since it doesn't kill the

The intent of the patch is to address such situations. Improving the
atari-atari code didn't seem to be easy, so I tried to modify the OWL
code instead, so that it can see such attacks.

I'm aware that the addition of new owl attack/defense codes is 
arguable. That's precisely the reason why I opened the discussion. :)


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