Lugdunum Stellar Crisis Services

SC Logo

The Bridier Ranking System for Stellar Crisis
Andy Graves, with thanks to Jerome Zago (Agt the Walker)

Stellar Crisis spacerule


The Bridier Ranking System, which I have attempted to implement in Stellar Crisis v3.01.22-beta with the intention of including it in the full v3.2 release, is a system used successfully in France for Chess rankings, and which has some features that make it particularly appropriate for use with an Internet-based game like SC.

Clearly then, it is designed to work for two-player games, and though it has been suggested that it could be successfully modified to work with many-player games, even those that permit alliances, while I'm not sure of the implications I've restricted myself to implementing it for Grudge games only at present. Therefore Bridier Ranking series is a series option in v3.01.22-beta, and when this code is installed at the main Lugdunum server I intend to make almost all the Grudge series there, be they Mirror or Traditional Maps, Longterms or Blitzes, whatever their configuration only provided they aren't Beginner games, into Ranking series.


The system aspires to justice by weighting the awards for victory and the penalties for defeat according to a function which takes into account both the difference in the competing players' ranks and an index of how well established those ranks are - that is, how many and how significant were the games on which the ranks were based. Thus each player carries two numbers into each game: Rank and Index.

Rank is the figure that is compared with others as an assessment of skill. The Top Ten lists will be ordered by Rank. Every player begins with a rank of 500, gains rank for a win and loses it for a loss, except in the case where the opponent's rank is so markedly different from the player's own that the system regards the conclusion as foregone. (Of course, should an upset occur, the rewards and penalties will be great). Therefore to gain in rank one must win against players of a similar rank to ones own or better; conversely to lose rank one must lose to players of similar rank or worse. This is the feature that makes Bridier particularly appropriate to counter the special difficulties of an Internet-based game - there is a strict limit on the amount of progress that can be made by nuking newbies and nukebabies.

Index can be seen as a measure of the volatility of the Rank figure. It ranges from 500, meaning untried, down to 100, meaning fully established. With every game played, some amount is subtracted from the index (in fact it is the same amount that is either added or subtracted from the Rank), until the player is considered established with an Index of 100. The only way to increase ones Index is to fail to play. An absence of three months from Ranking games will increase the Index of even an established player to at least 200; four months, 300; five months, 400; and a player who is absent for six months or more will carry a 500 Index that effectively represents its owner as untried. These changes to the Index do not affect the Rank, however, while the player remains absent - it affects only the weight which is given to that Rank in calculating the awards in games played on return.

This is another feature of Bridier that makes it approriate to use with Stellar Crisis. We have often seen the Top Lists, particularly the Averages and Nukes/Game Top Lists, inhabited by players who have gained an almost unassailable score in relatively few games, and have then retired that empire.


To minimize this kind of effect, I'm instigating two Bridier Top Ten Lists. The one which should be regarded most seriously is the Top Ten Established Players, as these are players who have played consistently well over many games. To qualify for this list you must have achieved the minimum Index of 100. It will not be possible to break into this list with a few quick wins over top players - though of course wins over better players will do more for the cause than those over weaker ones - and if you reach it and then retire your empire, you will fall off it again after three months. For a quite some time I anticipate that there will be no players on this list at all, so I'm also showing a Top Ten All Players list - by which I mean all participating players. It will list in order of Rank those players with an Index less than 495, thus excluding those who have played no Ranking games at all or none in the last six months.


Jerome's Original Proposal of Systeme Bridier as the ranking algorithm for SC, with formulae, and his suggested modifications for multi-player games.
Previous Next

Stellar Crisis spacerule

SourceForge Logo