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A Computational Study of the Role of Genetic Reuse in Evolvability

Seys, Chad William

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2012, Doctor of Philosophy, Case Western Reserve University, EECS - Computer and Information Sciences.

When creating a genetic algorithm one must decide how the phenotype is encoded in the genotype. This decision can change the “evolvability” of the system, that is, how quickly high fitness solutions are found. A change in encoding can cause high fitness solutions to be found more quickly or result in no high fitness solutions found at all.

Direct and indirect encodings are two general types of encodings. Direct encodings are characterized by one genotype parameter mapping to one phenotype parameter. Indirect encodings are characterized by a one-to-many genotype to phenotype parameter mapping.

Researchers have often demonstrated that indirect encodings have higher evolvability than direct encodings on a variety of problems. The indirect encodings were hypothesized to be more evolvable for two main reasons, both a consequence of the one-to-many property of the encoding. First, when parts of the genotype are reused, a given phenotype can often be described with a smaller genotype. A smaller genotype space should be faster to search than a larger genotype space. Second, the one-to-many property often leads to regularity in the phenotype produced by indirect encodings. This may be useful in exploiting regularities in the problems used for demonstrating that indirect encodings have higher evolvabilities than direct encodings.

This thesis explores whether reusing parts of the genotype increases evolvability more than size of the genotype for an example system. It is found that genotype reuse is more important than genotype size.

The thesis also explores whether an indirect encoding can increase evolvability and be selected for on a problem on which high fitness can be achieved with irregular solutions. It is found that it is very difficult to construct a problem which does not contain some form of regularity which can be exploited by the indirect encoding to increase evolvability. A problem which appears not to have regularity is found to have non-structural regularitiy. Based on this understanding, the problem is modified and the indirect encoding is found to have no or a slightly negative impact on evolvability on the modified problem.

Michael Branicky, PhD (Committee Chair)
Randall Beer, PhD (Advisor)
Hillel Chiel, PhD (Committee Member)
Ken Loparo, PhD (Committee Member)
Mehmet Koyuturk, PhD (Committee Member)
150 p.

Recommended Citations

Citations

  • Seys, C. W. (2012). A Computational Study of the Role of Genetic Reuse in Evolvability [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1341622098

    APA Style (7th edition)

  • Seys, Chad. A Computational Study of the Role of Genetic Reuse in Evolvability. 2012. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1341622098.

    MLA Style (8th edition)

  • Seys, Chad. "A Computational Study of the Role of Genetic Reuse in Evolvability." Doctoral dissertation, Case Western Reserve University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1341622098

    Chicago Manual of Style (17th edition)