### Points TWIXT PP

11 replies. Last post: 2003-05-23

Points
• Dan Mircea Vasilescu at 2003-05-19

Why I did not get any points for my game?

Game #50892 is finished.

Dan Vasilescu (silexu) old rating: 1688 newrating: 1688

==[ Beppi ]=> old rating: 1500 newrating: 1492

• David J Bush ★ at 2003-05-19

I believe the rating system here is the “Glicko” system, or something close to it. Besides the rating value, each player probably also has a “deviation” value which indicates how precise or dependable that rating is. This deviation is initially high, and decreases as you play more games and your rating becomes more “dependable.” You have completed 96 Twixt games. Beppi's loss to you was his first completed rated game. With no previously completed games, Beppi's initially assigned rating of 1500 is treated as an imprecise value by the rating algorithm. In other words, his deviation value is high, whereas yours is low. So, beating him doesn't say much about your rating, but his loss to you does increase the dependability of his rating.

Or, maybe it's a bug…

• Niall at 2003-05-19

Also, surely 1688 is much higher than 1500. I wouldn't expect much if I beat a 1312 player (assuming I could hold 1500 :-))

N

• ypercube at 2003-05-19

I don't know much about the Glicko system, but I know I have played about 300 hex games and in ALL of them the points I won were equal to the points the opponent lost or vice versa. So this result might be a bug or an indication that Twixt uses a different rating system than hex.

• Niall at 2003-05-19

I've checked this, when I lose to new people I only change by 2 or 3 points, they generally change by 14 or so.

That's in Hex too.

Niall

• Dvd Avins at 2003-05-19

I used to think we had something akin to the Glicko system, and I fear David may have taken his impression from something I posted a while ago which I know believe to be wrong.

Or rather, right but misleading. The good-old-fashioned USCF Elo system, with provisional ratings for players whov'e yet to complete a certain number of games, is a little like the Glicko system, except that the reliability measure of a rating is discreet (with only 2 values) rather than continuous. And that's what I think we're using here.

• Dan Mircea Vasilescu at 2003-05-20

Thank you for the answers. BTW in the second game with the same person I got 1 pct. Yeeeeeeeeees!

• David J Bush ★ at 2003-05-20

Provisional ratings can decrease if you win (against a low rated player), or increase if you lose (against a high rated player). In all the posts to all the forum topics, has anyone whined about losing rating points when they won? I sure don't see an example. I believe Richard deliberately avoided provisional ratings, and went with Glicko or something like it instead, to avoid this headache.

• Dvd Avins at 2003-05-20

I have seen variations of provisional ratings where any game which would cause you to move in the wrong direction is ignored. That's consistant with what I've seen here, as sometimes ratings don't move at all. Also, for veteran players, the number of points moved seems to depend only on the rating difference, not on the number of games played. That could be because that RD (the confidence measure) rapidly and asymptotically approaches some value, but I think think it's just fixed.

• beppi at 2003-05-23

Being a little expert of ratings, and of Glicko as soon as I implemented it for the Italian Othello Federation, I can say that with the little I have seen this is not Glicko, it looks like a simple Elo, without provisional ratings, that just doesn't give any variation to the opponent of a first-match gamer. In the game we're talking about, I think I decreased a little bit my rating, while Dan didn't. After that game, in Glicko I would have fallen to a very low rating, and begin oscillating a lot, but instead I look already very stable. If what Niall says is correct, then it may be implemented some kind of “very soft” Glicko.

• Niall at 2003-05-23

Well, I have some of the messages still, here are two reasonable examples:

http://www.littlegolem.net/jsp/message/message.jsp?msgid=98332

http://www.littlegolem.net/jsp/message/message.jsp?msgid=100206

I don't know if other people can access my msgs like this:

But basically, Roel was a new player at the time, his went down by 12 and mine only went up by 1. I was only 1581 at the time (and he was 1500)so the difference awsn't enough to account for this.

The second is against Julius Cezar, we were almost identically rated but he went up by 16 while I only moved down 8.

Hope this helps :-)

N

P.S. The reason, I think, ypercube hasn't experienced this is because being so highly rated he rarely plays people on 1500.