[Computer-go] CGOS source on github

Dan Schmidt dfan at dfan.org
Fri Jan 22 08:22:44 PST 2021

The primary purpose of a rating system is to predict the results of future
games accurately (this is the usual axiom, at least).

In a one-dimensional rating system, such as Elo, where each player's skill
is represented by a single number, it is impossible to have a (non-wacky)
system where A is expected to beat B in a two-player match, B is expected
to beat C in a two-player match, and C is expected to beat A in a
two-player match.

So if the players are eccentric in that respect, a one-dimensional rating
system is always going to have real problems with accurate predictions.


On Fri, Jan 22, 2021 at 10:54 AM uurtamo <uurtamo at gmail.com> wrote:

> also frankly not a problem for a rating system to handle.
> a rating system shouldn't be tweaked to handle eccentricities of its
> players other than the general assumptions of how a game's result is
> determined (like, does it allow for "win" and "draw" and "undetermined" or
> just "win").
> s.
> On Fri, Jan 22, 2021 at 6:29 AM David Wu <lightvector at gmail.com> wrote:
>> On Fri, Jan 22, 2021 at 8:08 AM Rémi Coulom <remi.coulom at gmail.com>
>> wrote:
>>> You are right that non-determinism and bot blind spots are a source of
>>> problems with Elo ratings. I add randomness to the openings, but it is
>>> still difficult to avoid repeating some patterns. I have just noticed that
>>> the two wins of CrazyStone-81-15po against LZ_286_e6e2_p400 were caused by
>>> very similar ladders in the opening:
>>> http://www.yss-aya.com/cgos/viewer.cgi?19x19/SGF/2021/01/21/733333.sgf
>>> http://www.yss-aya.com/cgos/viewer.cgi?19x19/SGF/2021/01/21/733301.sgf
>>> Such a huge blind spot in such a strong engine is likely to cause rating
>>> compression.
>>> Rémi
>> I agree, ladders are definitely the other most noticeable way that Elo
>> model assumptions may be broken, since pure-zero bots have a hard time with
>> them, and can easily cause difference(A,B) + difference(B,C) to be very
>> inconsistent with difference(A,C). If some of A,B,C always handle ladders
>> very well and some are blind to them, then you are right that probably no
>> amount of opening randomization can smooth it out.
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