"You are giving the program an arbitrary short term goal which may, or may not
be compatible with the long term goal of winning the game."
Don,
this is a very important consideration. How can an illusionary goal be better
than the real goal?
But I would argue that in the handicap situation, catching up quickly enough is
actually the real goal.
You write:
"And as the base program gets stronger this aspect of the program becomes more
and more of a wart."
This I disagree with. Because no matter how strong the program will become, it
will never find a way to defeat itself against a large handicap.
This is effectively what a program tries to do with its playouts.
The only reasonable alternative to trying to catch up quickly enough is to
model the weaker players errors straight into the playouts, and try to find a
direct win. But this seems more speculative to me than dynamic komi. Surely, it
is also harder to implement well.
Stefan
----- Original Message -----
From: Don Dailey
To: computer-go
Sent: Wednesday, August 12, 2009 11:11 PM
Subject: Re: [computer-go] Dynamic komi at high handicaps
The problem with MCTS programs is that they like to consolidate. You set
the komi and thereby give them a goal and they very quickly make moves which
commit to that specific goal. Commiting to less than you need to actually win
will often involve sacrificing chances to win. Sometime it won't, but you
cannot have a scalable algorithm which is this arbitrary.
However, if the handicap is too high, the program thinks every line is a loss
and it plays randomly. That's why we even consider doing this.
Dynamically changing komi could be of some benefit in that situation if there
is no alternative reasonable strategy, but it does not address the real
problem - which is what I call the "committal consolidation" problem. You
are giving the program an arbitrary short term goal which may, or may not be
compatible with the long term goal of winning the game. Whether it's
compatible or not is based on your own credulity - not anything predictible or
that you can scale. And as the base program gets stronger this aspect of the
program becomes more and more of a wart.
If this can be made to work in the short term, it should be considered a
temporary hack which should be fixed as soon as possible.
We have to think about this anyway sooner or later because if programs
continue to develop and the predictive ability of the playouts and tree search
gets several hundred ELO better, these programs may start to see more and more
positions as either dead won or dead lost. I'm sure we will want some kind
of robust mechanism for dealing with this which is better at estimating chances
that the opponent will go wrong as opposed to doing something that is a random
benefit or hindrance.
- Don
2009/8/12 terry mcintyre <[email protected]>
Ingo suggested something interesting - instead of changing the komi
according to the move number, or some other fixed schedule, it varies according
to the estimated winrate.
It also, implicitly, depends on one's guess of the ability of the opponent.
An interesting test would be to take an opponent known to be weaker, offer
it a handicap, and tweak the dynamic komi per Ingo's suggestion. At what
handicap does the ratio balance at 50:50? Can the number of handicap stones be
increased with such an adaptive algorithm?
Even better, play against a stronger opponent; can one increase the win
rate versus strong opponents?
The usual range of computer opponents is fairly narrow. None approach
high-dan levels on 19x19 boards - yet.
Terry McIntyre <[email protected]>
“We hang the petty thieves and appoint the great ones to public office.” --
Aesop
----------------------------------------------------------------------------
From: Brian Sheppard <[email protected]>
To: [email protected]
Sent: Wednesday, August 12, 2009 12:33:13 PM
Subject: [computer-go] Dynamic komi at high handicaps
>The small samples is probably the least of the problems with this. Do you
>actually believe that you can play games against it and not be subjective
in
>your observations or how you play against it?
These are computer-vs-computer games. Ingo is manually transferring moves
between two computer opponents.
The result does support Ingo's belief that dynamic Komi will help programs
play high handicap games. Due to small sample size it isn't very strong
evidence. But maybe it is enough to induce a programmer who actually plays
in such games to create a more exhaustive test.
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