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Method Description:
GENN - Applying grammatical evolution to optimize neural nets for detection and modeling of gene-gene interactions.
Genetically Programmed Neural Networks (GPNN) is a technique that utilizes genetic programming to optimize neural nets for classification and identification of gene-gene interactions.
Grammatical evolution (GE) is an evolutionary algorithm that uses linear genomes and grammars to define the populations. In GE, each individual consists of a binary genome divided into codons. Mutation takes place on individual bits but crossover only takes place between the codons. An individual or phenotype is produced by translating the codons using the grammar. The resulting individual can then be tested for fitness in the population and the usual evolutionary operators can be carried out. By using a grammar to define the phenotype, GE separates the genotype from the phenotype and allows greater genetic diversity within the population than other evolutionary algorithms.
Since GENN uses a grammar to define the structure of the resulting neural network, we can easily vary the behavior of the program with changes to the grammar. In GPNN the GP was constrained so that only valid neural networks can be produced. Any change to the behavior required changes to the code. The constraints for GENN are provided by the grammar itself and can be easily modified without modification of the code. For example, Boolean operators can be added or removed by changing only the grammar file used as an input to the program.
In addition, GPNN uses a binary tree for the genome and therefore, only two connections between nodes are possible. In GENN the grammar allows for defining multiple connections between nodes selected by the algorithm. Variable numbers of connections allows for more complicated neural networks to be evolved and potentially makes GENN more powerful than GPNN.
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