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C. FERREIRA Complex Systems, 13 (2): 87-129, 2001

Gene Expression Programming: A New Adaptive Algorithm for Solving Problems

Reproduction with Modification
According to fitness and the luck of the roulette, individuals are selected to reproduce with modification, creating the necessary genetic diversification that allows evolution in the long run.

Except for replication, where the genomes of all the selected individuals are rigorously copied, all the remaining operators randomly pick chromosomes to be subjected to a certain modification. However, except for mutation, each operator is not allowed to modify a chromosome more than once. For instance, for a transposition rate of 0.7, seven out of 10 different chromosomes are randomly chosen.

Furthermore, in GEP, a chromosome might be chosen by none or several genetic operators that introduce variation in the population. This feature also distinguishes GEP from GP where an entity is never modified by more than one operator at a time [9]. Thus, in GEP, the modifications of several genetic operators accumulate during reproduction, producing offspring very different from the parents.

We now proceed with the detailed description of GEP operators, starting obviously with replication. (Readers less concerned with implementation details of genetic operators may wish to skip this section.)

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