Perceptron is a rule-weighting algorithm based on artificial neural networks ("perceptrons") instead of [[GeneticAlgorithm]]s.  It is based on error back propagation by gradient descent and includes several security and accuracy-related modifications.  It has replaced the GA in the RescoringProcess for SpamAssassin 3.0.

Some info may be found at [[http://www.spamassassin.org/full/3.0.x/dist/masses/README.perceptron|masses/README.perceptron]] and at RunningPerceptron.