What is Phased Searching?
Within the SharpNEAT GUI, on the 2nd tab page there is a checkbox with the label ‘Enable Pruning’ which is checked by default. This enables a process whereby the average complexity of genomes in the population is tracked, and if it passes some threshold then the search switches to a ‘pruning’ mode. In pruning mode the search continues as normal but additive mutations are disabled and deletion mutation rates are increased, this causes the average structural complexity of genomes in the population to fall but without loosing the best genomes. This can give rise to new bursts of improvement in fitness and also a speedup of the search, since more complex genomes take longer to evaluate. For a more complete explanation see the experimental write-up – Phased Searching with NEAT: Alternating Between Complexification And Simplification.
