Don Daily wrote:
>so for instance a professional player with a relatively low professional
>ranking does not need as many stones
>as indicated by his opponents ranking to beat another professional WHO IS
>SEVERAL RANKS HIGHER.
For centuries pro ranks were defined by the handicap required against other
pro's. But the difference between pro dans is smaller than a stone per rank.
rank difference => handicap
0p => alternating black and white
1p => black in two out of three games
2p => black in all games
3p => two stones in one out of three games, black in two out of three games
4p => two stones in two out of three games, black in one out of three games
5p => two stones in all games
...
8p => three stones in all games
These were the handicaps defining pro ranks in Japan up until 2003
(in 2003 they dropped the handicap system but it was not changed into a rating
system either http://senseis.xmp.net/?NihonKiInNewPromotionSystem
<http://senseis.xmp.net/?NihonKiInNewPromotionSystem> . In fact I think the new
system seems quite arbitrary and unpredictible):
Dave de Vos
________________________________
Van: computer-go-boun...@computer-go.org namens Don Dailey
Verzonden: zo 7-6-2009 18:10
Aan: computer-go
Onderwerp: Re: [computer-go] bots and handicaps (Re: New CGOS)
Here is why the handicap system is broken. We can talk about how the ELO
system is broken in another discussion but it is too.
At 1 or 2 stones difference, the handicap system works well. At greater
handicaps it's skewed. The "coincidence" that I'm talking about is that it
works to a reasonable degree at larger handicaps.
The handicap system is based on the idea that no matter what your level of
play, you can give 7 stones to a player 7 stones weaker. Everyone knows
this is not true. It is very accurate at low handicaps, and progressively
less accurate at high handicaps (as well as high levels) so for instance a
professional player with a relatively low professional ranking does not need as
many stones as indicated by his opponents ranking to beat another professional
WHO IS SEVERAL RANKS HIGHER.
Is this not correct? When I say it's imperfect, that is what I am talking
about.
There is nothing wrong with defining 1 stone handicap as a "rank" and I don't
view that definition as imperfect and that is a reasonable basis for defining
the ranking system in GO. What's imperfect is the assumption that 9 stones
makes it a perfectly even match if you are 9 ranks apart no matter where along
the scale you are.
If you wanted to know what handicap is needed to win a match at various
handicaps from beginner to world chamption, you would need a 2 dimentonal
table lookup because it's not as simple as just taking the difference in their
rankings. With the table lookup and a huge amout of data to back it up, you
would have a predictor as good as ELO.
Does that clarify what I meant when I said the handicap system is imperfect?
As we discussed many times on this forum and in private email, a one stone
handicap has a different meaning at different levels - it's just an awkward
system to deal with mathmatically on a go server for computers where wild
mismatches will be common.
the fact that chess doesn't have a fine-grained way to
handicap a game, in fact, the fact that most games don't,
doesn't mean that it's hard to deal with.
There are simple ways to deal with it. One could simply increase or decrease
your rank as soon as you start winning or losing you games at your current
handicap level. We don't need ELO for that and it's simple to do.
What I see on most servers and in this modern day and age is a move away from
the centuries old system, not an embrace of it as being superior. Of course
I understand there is a sentimental attachment to it. It was like this in
chess many years ago when the old fashion descriptive chess notation was
replace in the USA with algebraic notation in order to stay with the modern
world and to many people it was just not chess anymore.
my guess is that any go playing program that doesn't
depend upon an opening book for a lot of its strength
is going to adapt just fine. experiments between players
of different CGOS-measured strengths could find this out for
sure -- time for another set of experiments? i'll donate some
cpu time.
It took a lot of work and energy to do these studies - I'll have to think about
this one.
Of course they would adapt if that was the system. Even if this idea was not
good for current MCTS programs they would adjust is that was what was required
to do well in competition.
if it helps to encourage the authors, just keep in mind
that winning with handicap is extremely convincing
evidence to "regular go players" that one player is much
stronger than another. plus, it takes exponentially fewer
games to determine that difference.
with a logarithmic (in range of handicap, say, +/-6 stones)
number of games you could get a very accurate view of
the strength difference between two players. say, take
best of 2 out of 3 at each test level and do binary search.
some go clubs just keep track of the relative difference
in stone strength between pairs of players, requiring, say, a
3-win streak by one player to adjust the handicap by a
single stone.
alternatively, you can (somewhat cheesily) map ELO
to handicap and vice-versa for a limited range of ELO
and handicap.
Like I say, a table will do it, and I believe some kind of formula could be
fitted to the data.
- Don
s.
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