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Re: [gnugo-devel] regress endgame:603
From: |
Evan Berggren Daniel |
Subject: |
Re: [gnugo-devel] regress endgame:603 |
Date: |
Fri, 11 Apr 2003 11:30:36 -0400 (EDT) |
On Fri, 11 Apr 2003 address@hidden wrote:
>
> > By my count, G6 is 2.5 miai and C1 is 3 miai, but tedomari concerns mean
> > that G6 is the correct play for black, and C1 is the correct play for w.
> > Is this incorrect somehow? I'm not terribly confident in my endgame
> > counting, but that's how I read it...
>
> G6 is the best point for either player in this position. However
> there may to be a (sort-of) valid reason for having the engine
> prefer C1, as I will explain.
>
> G6 is 5 points gote. C1 is 3 points reverse sente.
>
> Whether 5 points gote or 3 points reverse sente is preferrable
> depends on the whole board position.
>
> It's sente for W to hane at D1. The difference on the board between
> W:D1 B:E1 W:C1 B:F2 and B:C1 W:B1 B:D1 is 3 points. The points
> at issue are at B1, E1 and F2.
>
> The difference between B:G6 and W:G6 is 5 points.
I'm agreed here. My reference for miai counting:
http://senseis.xmp.net/?MiaiCounting
The idea is that since there are two net plays between B:G6 and W:G6, each
of those plays is worth half of the 5 point difference, or 2.5 points.
Because the D1 hane is sente for w, there are 0 net stones if w makes the
hane, and 1 net stone played if b plays the revers sente. So there is one
stone difference, and the reverse sente is valued at three points.
The problem here is that if b takes C1, then w gets tedomari (the last
play) with G6. If b G6, then b gets the last play when w plays the D1
sente hane.
For a good explanation:
http://senseis.xmp.net/?tedomari
It looks to me like black should make a sacrifice of half a point in order
to get tedomari in this position.
Adding a 3 point gote to the board would definitely be a good solution.
Perhaps also leaving this problem but marking it as a difficult problem.
>
> If there is another yose point on the board it is conceivable
> that a 3 point reverse sente move would be preferrable to a 5 point
> gote position. Suppose that it's like this:
>
> [3 point reverse sente] [5 points gote] [3 points gote].
>
> If B takes the 3 point reverse sente, then W takes the 5 gote,
> B takes the 3 gote, then B gets 6 points and W gets 5. If
> B takes the 5 gote then W gets both the other two by taking
> his sente first.
>
> But in this position, there is no third yose point. Each
> player will get one of the two plays and it's better to
> chose the big one.
>
> I think the point of the problem is that it is supposed to
> be policy to prefer a 3 point reverse sente to a 5 point gote.
> The engine does endgame analysis locally without taking into
> account what other local games (in the sense of combinatorial
> game theory) exist on the board. A real combinatorial endgame
> engine would definitely prefer G6 in this position, and the
> problem could be revised by placing another 3 point gote
> position on the board.
>
> The test was submitted by Gunnar in this archive link:
>
> http://mail.gnu.org/archive/html/gnugo-devel/2002-09/msg00390.html
>
> Dan
>
>
>
>
> _______________________________________________
> gnugo-devel mailing list
> address@hidden
> http://mail.gnu.org/mailman/listinfo/gnugo-devel
>
>
- Re: [gnugo-devel] test results after removing Pattern CD106, (continued)
- [gnugo-devel] regress endgame:603, kevin yong, 2003/04/10
- Re: [gnugo-devel] regress endgame:603, bump, 2003/04/11
- Re: [gnugo-devel] regress endgame:603, Evan Berggren Daniel, 2003/04/11
- Re: [gnugo-devel] regress endgame:603, bump, 2003/04/11
- Re: [gnugo-devel] regress endgame:603, Arend Bayer, 2003/04/11
- Re: [gnugo-devel] regress endgame:603, bump, 2003/04/11
- Re: [gnugo-devel] regress endgame:603, Arend Bayer, 2003/04/11
- Re: [gnugo-devel] regress endgame:603,
Evan Berggren Daniel <=
- Re: [gnugo-devel] regress endgame:603, bump, 2003/04/11
- Re: [gnugo-devel] regress endgame:603, Evan Berggren Daniel, 2003/04/11
- Re: [gnugo-devel] regress endgame:603, bump, 2003/04/11
- Re: [gnugo-devel] regress endgame:603, Arend Bayer, 2003/04/11
- Re: [gnugo-devel] regress endgame:603, Evan Berggren Daniel, 2003/04/11
- Re: [gnugo-devel] regress endgame:603, Evan Berggren Daniel, 2003/04/11
- Re: [gnugo-devel] regress gunnar:8, kevin yong, 2003/04/11
- [gnugo-devel] regress lazarus:1, kevin yong, 2003/04/12
- Re: [gnugo-devel] regress lazarus:1, Evan Berggren Daniel, 2003/04/12
- Re: [gnugo-devel] regress lazarus:1, bump, 2003/04/13