Re: computer-go: A problem with understanding lookahead

[Jan van der Steen <J.van.der.Steen@xxxxxxxxx>]

GL7: David Elsdon wrote:
> 
> Hello all,
> 
> I have a serious problem with lookahead. I don't understand why it works.
> Why should the backed up values of a, say, 7 ply full width alpha-beta
> minimax search be any better than the values my evaluation function gives
> me by simply evaluating the positions at ply 1. I can understand that if
> the end of the game is in sight then lookahead is useful. I can
> understand  that if I use a quiesence measure or some such and only
> evaluate positions when I know that my evaluation function will work best
> then lookahead is useful. But if neither of these is the case then does
> lookahead help. Is there some way in which the backing up of values and
> minimaxing somehow reduces the error in the evaluations.
> 
> I really am seriously stuck with this one.

If the evaluation function is perfect then you're right that
only one ply is enough. But compare it with real life: you
judge a position and check the evaluation by playing out some
sequences. The same with computers, by investigating the position
a few moves you can check if the cut indeed works, or the group
indeed is alive.

Jan van der Steen