Re: [gnugo-devel] Patch arend_1_14.2 -- Missing endgame pattern

[Inge Wallin]

I think Gunnar and Dan has done a very good job of describing the
valuation principles that  Gnu Go uses.  I will just throw in a few
comments. 

Gunnar wrote:
> Arend wrote:
> > I have another very general question about GnuGo's move valuation.
>
> We see that this makes a difference in territory of 4, which is what
> influence_delta_territory() should report. Then we have the question
> of sente, reverse sente and double sente. This is implemented by the
> concepts of followup_value (sente) and reverse_followup_value (reverse
> sente) and is a lot less exact. Basically certain patterns try to
> detect whether there are more points to gain if we are allowed another
> move in a row and add a followup_value. Other patterns try to decide
> whether the opponent would have more points to gain by two moves in a
> row in the local area and add a reverse_followup_value. These followup
> values are added to the territorial value so that a sente move (high
> followup_value, no or low reverse_followup_value) and reverse sente
> move (no or low followup_value, high reverse_followup_value) both get
> about double the value, while a double sente move (high followup_value
> + high reverse_followup_value) gets still more. The double sente value
> computation is probably not very good.

Indeed it is not, since the two players in a a double sente situation
often has to play on different intersections.

Another weakness that often leads to undervaluation of moves that
venture into the opponents territory is that followups of the
followups are never taken into account.  The value of entering into
the enemys moyo is of course not only the potential territory that we
destroy now, but also half of the followup and half of half of the
followup followup and so on.

And another weakness is that there really isn't any notion of sente
and gote sequences at all.  We never know when we start a sequence if
it will lead to gote. We just know if there is a followup move with
some value attached.

        -Inge