Amby,
Quick answer if you want to look for yourself:
try the wiki to see the current calculation (not completely up to date as I detail below):
http://www.vdiplomacy.com/wiki/index.php?title=Rating
and if you wish, take a look a the code directly (should be up to date if I remember correctly):
https://github.com/Sleepcap/vDiplomacy/blob/master/lib/rating.php
Anyways, I've been wondering these things too, for you and several other individuals.
So... I took a look at your games and immediately found one thing odd from the Bourse game (http://www.vdiplomacy.com/hof.php?
gameID=9186).
At first glance:
When I look at the calculation for that game, the score calculation for each player should include a calculation against every other player, but closer inspection shows that you only scored against those of us who were defeated, while those of us who were defeated only lost points to those of you who drew (and Canaduh, who CD'd).
As I understand, the calculation should be made for every player against every other player.
So I took a closer look:
This game is PPSC not WTA, and one player CD'd (Canaduh) was replaced (by bozo).
In this particular game, bozo took over basically from the beginning and was defeated along with 8 others of us. That left 6 players drawing the game at the end and the 1 CD.
This variant has 109 SC's, 55 of which are needed for a win, which is 1/2 + 1, so this game had no arbitrary victory conditions.
Rr (Real result)
mV (match value)
Rr for draw vs draw is unknown as draw vs draw doesn't appear in the calculations for this game, but it should be 0.5 : 0.5.
Rr for draw vs defeat should be 1 : 0 (which it is)
Rr for defeat vs defeat should be 0.5 : 0.5, but this calculation is absent too.
Rr for defeat vs CD/Resign should be 1: 0 (which it is)
These values should take care of any performance relationships in the game between these players and mV should be left out of this calculation.
Instead, mV for draw vs defeat looks to be 17% (or 1/6th of the draw), but this sort of comparison should only be in effect between drawing players and not drawing vs defeated players. Each drawing player should get 1/6th of the credit for the game (adjusted by their expected performance), but instead the match value is scaled to 17% of the score adjustment because of the size of the draw which makes absolutely no sense. (This is the issue with trying to use mV to account for proportional differences in SC's instead of Rr where this relation should be).
From the wiki:
Adjustments for each match (matchValue=mV):
- Value the importance of take-overs. (If a player bet only the half the whole match is worth only half.)
- Normalize the mV by the SC% difference of both players
The first adjustment makes sense so that picking up a CD doesn't allow players to quickly inflate their ranking. This explains why drawing against a defeated bozo who didn't bet as much as the rest of us is adjusted differently than for the rest of us (or for canaduh who CD'd).
The second reason makes no sense whatsoever because the calculation for Rr1 and Rr2 should take into account the proportion of SC's between the players in a PPSC game (as shown in the wiki, but not implemented in the code). mV should not be adjusted further to make this comparison again. (Also Oli as I understand, you have made it so that Rr always either 1 or 0 for all games. This makes sense for WTA or maybe even solo vs survive in PPSC, but not survive vs survive which is where any effects from different SC counts at game end should be made, not in mV.)
So I took a look at another known world game to see what happens with a solo'd PPSC known world game:
http://www.vdiplomacy.com/hof.php?
gameID=4761cypeg got at best 51% mV against defeated players (he solo'd) and got ~32% mV against those of us who he beat but had sizable survives (19 and 20 SCs), and more against others who only had 7SC's.
mV is being used here to make the comparison between SC's rather the Rr which results in scaling of the resulting score calculation and confuses and ruins the intended effect.
If cypeg's Re (expected result) against me was 65% (which appears to be calculated correctly), and his actual result was 100% (he beat me), then he shouldn't get only 32% of the rating adjustment simply because I got 20SC's. cypeg won, and by a lot. (I'm not exactly sure where the value 32% came from because mV still isn't completely explained on the wiki and I couldn't follow it in the code).
Additionally, against players cypeg defeated, he is getting only 51% of his ratings adjustment because he didn't capture every last one of the 109 SC's. This is wrong, he should get 100% of the ratings adjustment for wining against defeated players.
Further.. comparing Wolfman and I:
Wolfman's expected result (Re) against me was 28% while mine against him was 72%
However my real result (Rr) against Wolfman was 100% (I had 20 SC's) while his against me was 0% (he had 19 SC). Our real results should have been pretty darn close to 50%:50% against each other. Instead Wolfman is getting a complete fail against me for getting 1 less SC than I had. Turns out in the actual calculation, this doesn't make much difference because for each of us the final ratings adjustment is scaled down to 1% because we were so close in SC's. Wolfman's real result actually should have beat his expected result against me ~50% to 28% but instead he lost (a thankfully for him scaled to 1%) ratings adjustment of an expected 28% to a real result of 0%. While the numbers come out not looking horribly skewed, the calculation being done is completely wrong and doesn't have the intended effect. Wolfman should have gained in the ratings adjustment while I went down.
Am I making sense to anyone else in identifying what is wrong here?
WorldDipCon and such
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