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58 lines
3.2 KiB
Plaintext
58 lines
3.2 KiB
Plaintext
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Hi there!
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Thanks for downloading this code and opening up this file. The goal of this
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project is to provide an annotated reference implementation of Microsoft's
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TrueSkill algorithm.
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I describe the philosophy and the buildup of the math involved in my blog post
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"Computing Your Skill" available at moserware.com.
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In addition, there is a math paper that goes along with the blog post that explains
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most of the more technical concepts.
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This project isn't intended to win performance tests, it's meant to be read
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and understood. If you see ways to improve its clarity, please submit a patch.
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If you just want to use the TrueSkill algorithm, simply use the TrueSkillCalculator
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class and enjoy. If you need examples, please look in the UnitTests\TrueSkill folder.
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If you want to understand the inner workings of the algorithm and implement it
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yourself, look in the Skills\TrueSkill folder. There are three separate
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implementations of the algorithm in increasing levels of difficulty:
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1. TwoPlayerTrueSkillCalculator.cs is the easiest to follow and implement. It uses
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the simple equations directly from the TrueSkill website.
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2. TwoTeamTrueSkillCalculator.cs is slightly more complicated than the two player
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version and supports two teams that have at least one player each. It extends
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the equations on the website and incorporates some things implied in the paper.
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3. FactorGraphTrueSkillCalculator.cs is a wholly different animal than the first two
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and it is at least an order of magnitude more complex. It implements the complete
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TrueSkill algorithm and builds up a "factor graph" composed of several layers.
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Each layer is composed of "factors", "variables", and "messages" between the two.
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Work happens on the factor graph according to a "schedule" which can either be
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a single step (e.g. sending a message from a factor to a variable) or a sequence of
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steps (e.g. everything that happens in a "layer") or a loop where the schedule runs
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until values start to stabilize (e.g. the bottom layer is approximated and runs until
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it converges)
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TrueSkill is more general than the popular Elo algorithm. As a comparison, I implemented
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the Elo algorithm using the both the bell curve (Gaussian) and curve that the FIDE chess
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league uses (logistic curve). I specifically implemented them in a way to show how the
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only difference among these Elo implementations is the curve. I also implemented the
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"duelling" Elo calculator as implied in the paper.
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Everything else was implemented to support these classes. Note that a "player" can be an
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arbitrary class. However, if that player class supports the "ISupportPartialPlay" or
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"ISupportPartialUpdate" interfaces, you can add these extra parameters. The only calculator
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that uses this info is the factor graph implementation. See those files for more details.
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I use this code personally to rank around 45 people, so it's important that it's accurate.
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Please let me know if you find errors. Bug fix patches are strongly encouraged! Also, feel
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free to fork the project for different language implementations.
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I'd love to hear from you via comments on the "Computing Your Skill" blog post.
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Have fun and enjoy!
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Jeff Moser <jeff@moserware.com>
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