Go Journey

Here are my own two cents to the topic.
I’ve tried to reverse engineer the OGS rating system, so my main sources of knowledge about the OGS rating system are based on forum posts and my own tests.

This is rather long because I added some unnecessary comments.

The rating is normally displayed as follows

PlayerName 1150 ±350

The above is actually the rating given to new players on the server

You cannot know, but the initial rating is actually 1500±350 as the glicko2 spec suggests.
For new players (high deviation) the rating gets lowered for displaying (and hopefully for match making as well). This was proposed to give new players easier games to start with go on OGS. It was called humble rating on the forum. The rating is shown correct if the deviation is lower than 125.
I’m not sure how one would correctly show the humble rating, but 1150+700 would be more precise.

When trying to matchmake this also provides a wide range of potential opponents.

I don’t know how other sites do it, but I’m pretty sure OGS doesn’t take deviation into account for match making.

As an example let us assume the above player plays an opponent 1200 ±80

If he wins then his rating might increase 100 to 1250 and his RD (rating deviation) drop to ±340. His opponent may drop to 1190 and his deviation ±79

Just as a service: The changes are
1150±350 → 1351±252
1200±80 → 1187±80 (acually 79.728…)
1500±3500 → 1572±285
1200±80 → 1194±80

so is assuming that the first player was at the strong end of the band and not the weak.

Actually it’s a general wight, but for the sake of understandability it might be ok.

Player A 1800 ±80 beats player B 1600 ±100

A 1800±80 → 1809±79
B 1600±100 → 1587±98

Player C 1700 ±80 beats Player D 1800 ±80

This has more of an impact as the system thought Player D was stronger . Result

Player C 1780 ±85 Player D 1720 ±90

C 1700±80 → 1722±79
D 1800±80 → 1778±79

A single game result (always) results in a lower deviation. Glicko2 usually uses a bunch of games (up to 15 on OGS) to update the rating. Only if there are many outliers the deviation goes up (at least this is my observation). (A ?bug? on OGS causes the deviation to go up after a completed rating periode (15 games)).

glicko 2 also adds in a volatility factor

just as info: on OGS the volatility is about 0.06 and doesn’t change much.

The system also has a RD time decay included so if you don’t play for a long time then your RD increases as the system grows less certain of you.

Not sure if OGS implements this special case. I came to the conclusion it doesn’t.

GO Server system

The rating is both board (9x9, 13x13, 19x19) and game type based (i.e blitz, normal etc) so each player has a different rating for each combination. This is then combined into an overall rating.

The overall rating is the rating used everywhere on OGS. The other ratings are just “informational”.
Each of those ratings is calculated separately. The overall rating uses all games and the opponents overall rating, the 19x19 blitz uses only 19x19 blitz games and the opponents 19x19 blitz ratings and so forth.

My start rating 1150 ±350

As mentioned above, it’s actually 1500±350. You can see your true rating here.

though this should not impact a decent ratings system only the win/loss should count

that’s correct.

This is because my rating band was so wide the system is treating their win as an ‘expected’ win

I’m not sure if calling it ‘expected’ is the best phrase here. Because of the high uncertainty, the system doesn’t even know what to expect.

Note how the 1150 for all the other board/games types is increasing the 0 - 0 rating (which is the prime site rating displayed against the user name). The actual rating is the 19x19 and times 742.

See above. This are 4 independent ratings and the overall number is the actual one.

Kyu-Dan designation which drops to the alarming level of 41k!And increases to 11th dan.

OGS limits the rank to 25k as the lowest and the highest to 9d.
The upper bound is by tradition? The lower bound of 25k around the point where the separation in different ranks looses its meaning.
The Kyu and Dan ranks are the traditional way to classify player strength. A rank difference of one rank equals a one stone handicap.
On OGS there is a direct convention formula rating → rank, with rating = 850 * exp(0.032 * rank) where rank 0 is 30k.
The deviation is calculated by converting either the 1 sdt lower or higher rating. (I’m not sure which is used).

Official GO Kyus also start at 30 kyu for a total beginner whereas this system seems to drop you to 41 Kyu.

It only looks this way because the histogram applied the formula to the ratings. OGS doesn’t drop you below 25k, but your rating can drop lower.

as noted I am guessing ‘Kyu’

you guessed right.