I'm not sure what POSi or NEGi are (you can have multiple winners, and everyone else loses?), but it seems like you want an algorithm that takes past performanc

I'm not sure what POSi or NEGi are (you can have multiple winners, and everyone else loses?), but it seems like you want an algorithm that takes past performance into account, and, and allows for variability in performance. You need to keep track of 2 numbers for each player, their rank and their weight. I don't see any reason why your algorithm would do this accurately by design, but it might work out. Have you heard of TrueSkill[1,2]? It supports multiple players in a single game, and is based on a concrete assumption of what a player's skill is. This also keeps track of 2 numbers per player, their mean skill and its standard deviation. The one thing that may be different about it is that there is no way to tell the algorithm the degree of a win, just the relative rankings of each player. [1] http://research.microsoft.com/en-us/projects/trueskill/ http://research.microsoft.com/en-us/projects/trueskill/ [2] http://www.moserware.com/2010/03/computing-your-skill.html http://www.moserware.com/2010/03/computing-your-skill.html