[gnugo-devel] Re: snapbacks

[Gunnar Farnebäck]

Dan wrote:
> Recently I've seen GNU Go take snapbacks on a number
> of occasions.
> 
> Here's an example. Current CVS plays W at Q7. This
> is a contrived example but this sort of thing does
> happen in actual play.

Interesting.

>   Q7: owl attack/defend for R6
>   Q7: owl attack/defend for S8
>   Q7: owl attack/defend for S6
>   Q7:   2.33 (followup) - threatens to capture Q6
>   Q7: not a safe move
>   Q7: 17.01 - change in territory
>   Q7:   7.20 - S8 strategic value already counted - A.
>   Q7:   2.80 - R6 strategic value already counted - A.
>   Q7:   3.60 - S6 strategic value already counted - A.
>   Q7: 3.17 - strategic effect on Q5
>   Q7:   13.40 - total followup value, added 11.07 as territorial followup
>   Q7: 6.70 - added due to followup (13.40) and reverse followup values (0.00)
>   Q7: 1.24 - shape (shape values +1.00(1) -0.00(0), shape factor 1.050)
>   Q7: 1.09 - connects strings (connect value 10, shape factor 0.219)

I don't have a problem with it having a high value since it does solve
the problems it claims, although only temporarily, but it should be
valued lower than the effective move, in this case T6. Now it's 29.21
for Q7 and 28.90 for T6 so a simple workaround would be to add a
modest negative shape value for playing into snapback. There are,
however, oddities in the territorial valuation, which maybe should be
investigated first.

/Gunnar