If we are going to solve a combinatorial problem, we should use an enumerated chromosome.  Enumerated chromosomes, unlike continuous chromosomes, may have very flexible lengths and alphabet sizes.  The two parameters are defined strictly by the problem to be solved.  These two parameters may or may not be related, depending upon how the problem parameters are coded into an enumerated chromosome.

As we already know, each position within a chromosome is called a gene.  The term "alphabet" is used to denote the whole range of possible values (alleles) of the chromosome’s genes.  The total number of genes in the chromosome is called the chromosome length.

In GeneHunter, two types of enumerated chromosome representation are implemented.

Repeating Representation

In repeating representation, each gene may have any value from the whole range of the alphabet, independent of the value in any other gene in the chromosome.  Any “letter” from the alphabet may be found in the chromosome an arbitrary number of times.

Unique Representation

In unique representation, the value of the chromosome length may be smaller than or equal to the size of the alphabet, but it may not be greater than the alphabet size.  Therefore, each gene has a unique value from the alphabet, so there are no duplicates among gene values in the chromosome.  The unique representation is included in order for GeneHunter to solve such combinatorial problems as the Traveling Salesman Problem.