Locally geometric semantic crossover: a study on the roles of semantics and homology in recombination operators

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  author =       "Krzysztof Krawiec and Tomasz Pawlak",
  title =        "Locally geometric semantic crossover: a study on the
                 roles of semantics and homology in recombination
  journal =      "Genetic Programming and Evolvable Machines",
  year =         "2013",
  volume =       "14",
  number =       "1",
  pages =        "31--63",
  month =        mar,
  publisher =    "Springer",
  keywords =     "genetic algorithms, genetic programming, Geometric
                 crossover, Semantics, Library, Spatial index, Kd-tree,
  ISSN =         "1389-2576",
  DOI =          "doi:10.1007/s10710-012-9172-7",
  size =         "33 pages",
  abstract =     "This study presents an extensive account of Locally
                 Geometric Semantic Crossover (LGX), a
                 semantically-aware recombination operator for genetic
                 programming (GP). LGX is designed to exploit the
                 semantic properties of programs and subprograms, in
                 particular the geometry of semantic space that results
                 from distance-based fitness functions used
                 predominantly in GP. When applied to a pair of parents,
                 LGX picks in them at random a structurally common
                 (homologous) locus, calculates the semantics of
                 subprograms located at that locus, finds a procedure
                 that is semantically medial with respect to these
                 subprograms, and replaces them with that procedure. The
                 library of procedures is prepared prior to the
                 evolutionary run and indexed by a multidimensional
                 structure (kd-tree) allowing for efficient search. The
                 paper presents the rationale for LGX design and an
                 extensive computational experiment concerning
                 performance, computational cost, impact on program
                 size, and capability of generalisation. LGX is compared
                 with six other operators, including conventional
                 tree-swapping crossover, semantic-aware operators
                 proposed in previous studies, and control methods
                 designed to verify the importance of homology and
                 geometry of the semantic space. The overall conclusion
                 is that LGX, thanks to combination of the semantically
                 medial operation with homology, improves the efficiency
                 of evolutionary search, lowers the variance of
                 performance, and tends to be more resistant to
  notes =        "Open Access",
  affiliation =  "Institute of Computing Science, Poznan University of
                 Technology, Poznan, Poland",

Genetic Programming entries for Krzysztof Krawiec Tomasz Pawlak