Yes, in its present instantiation, SlugGo is inadmissibly selective.
In this case, we clearly see that after some small number, more
plies of global search result in worse play.
I do not have any expectation of perfect play, only improvement
over the present state of things.
Cheers,
David
On 3, Dec 2007, at 1:46 PM, Don Dailey wrote:
David Doshay wrote:
On 22, Nov 2007, at 9:35 AM, Don Dailey wrote:
This is one of many things in life that people refuse to believe -
regardless of the evidence. ...
Instead, people focused on highly selective searches. In order to
play strong it was clear that computers would have to look 20 or
30 ply
ahead
Our experience with SlugGo is that playing strength peaked only
a few ply deep in global lookahead. Our conclusion was that for
deeper lookahead the evaluation function that was used at the
leaf nodes became irrelevant because the real game was off in a
different branch than any of our expected paths. I would call our
tree "somewhat selective" near the top, but increasingly selective
deeper into the tree, so I am not sure how our results map onto
your argument.
If your program is inadmissibly selective (you prune off a branch that
will never be recovered again) then your program will peak out at
some
depth well below perfect play. You cannot recover if you prune
away
an important move.
There is something that the latest Monte Carlo programs have in common
with the best chess programs - and seems to be the right way to
structure a game tree search. Your selectivity should be
progressive. In order to do this correctly you must re-visit nodes
many times. Chess programs do it iteratively and Monte Carlo UCT type
programs do it "best first" fashion. So the decision to prune any
given
move is a decision that is considered many times in the course of a
search - each time taking advantage of additional information.
I think you are exactly correct when you say the "real game was off
in a
different branch" - it is a branch that get's pruned away forever
in SlugGo.
I think you probably do get more strength with each depth
increase, but
the extra strength approaches some limit (that you are already very
close to) asymptotically. Ok, maybe it's not technically asymptotic
because Go is not infinite, but you get the point.
- Don
If your argument is that it is worth exploring the entire tree to
whatever depth is possible, then our results are probably not
really evidence to the contrary.
Cheers,
David
_______________________________________________
computer-go mailing list
computer-go@computer-go.org
http://www.computer-go.org/mailman/listinfo/computer-go/
_______________________________________________
computer-go mailing list
computer-go@computer-go.org
http://www.computer-go.org/mailman/listinfo/computer-go/
_______________________________________________
computer-go mailing list
computer-go@computer-go.org
http://www.computer-go.org/mailman/listinfo/computer-go/
