Genetic operators
This presentation is the property of its rightful owner.
Sponsored Links
1 / 20

Genetic Operators PowerPoint PPT Presentation


  • 60 Views
  • Uploaded on
  • Presentation posted in: General

Genetic Operators. Reproduction Crossover Mutation Permutation Editing Encapsulation Decimation Inversion Hoist Create Compress Expand. Reproduction. A parent is chosen from the population (using one of the selection methods). The individual is copied into the next generation.

Download Presentation

Genetic Operators

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Genetic operators

Genetic Operators

  • Reproduction

  • Crossover

  • Mutation

  • Permutation

  • Editing

  • Encapsulation

  • Decimation

  • Inversion

  • Hoist

  • Create

  • Compress

  • Expand


Reproduction

Reproduction

  • A parent is chosen from the population (using one of the selection methods).

  • The individual is copied into the next generation.

  • The fitness of the individual does not have to be calculated.


Crossover

Crossover

  • Two parents are selected from the population.

  • A crossover point is selected in each individual randomly.

  • The subtrees rooted at the crossover points are swapped.

  • In some cases the crossover operator can be reduced to mutation or reproduction.

  • A limit is usually set on the offspring size.

  • Variations of crossover


Crossover example

Crossover Example

Crossover Fragments


Mutation

Mutation

  • A parent is selected from the population.

  • A mutation point is selected at random.

  • The subtree rooted at this point is removed and replaced with a newly created subtree (could be a terminal).

  • Variations of mutation.

  • Can be reduced to reproduction.

  • Is used to maintain genetic diversity.


Mutation example

Mutation: Example


Permutation

Permutation

  • A parent is chosen from the population.

  • A function node is randomly selected.

  • A permutation of the function arguments is randomly selected.

  • If the arity of the function node is two, the arguments are merely swapped.


Permutation example

Permutation Example


Editing

Editing

  • Is used to remove redundant code.

  • A parent is selected.

  • Examples

    • (+ 1 2 ) will be replaced by 3

    • (/ x 1) will be replaced with x

    • (AND T T) will be replaced with T

  • GP Parameters

    • A frequency parameter

Effect on Diversity


Encapsulation

Encapsulation

  • Selection a parent.

  • Select a function node at random.

  • Remove the subtree rooted at this node.

  • This subtree forms the a new function and is given a label, e.g. E0, E1, etc.

  • The new function is added to the terminal set as it does not have arguments.


Encapsulation example

Encapsulation Example


Decimation

Decimation

  • Is to prevent loss of genetic diversity.

  • A percentage of the population is deleted during the specified generations.

  • Usually starts with a larger population.

  • GP parameters

    • Application rate

    • Frequency Rate


The inversion operator

The Inversion Operator

  • Select a parent.

  • Select two subtrees randomly.

  • Swap the subtrees.

  • Subtrees to be swapped must not be contained in each other


Inversion example

Inversion: Example


Hoist

Hoist

  • Select a parent.

  • Randomly select a subtree within a the parent.

  • Copy the subtree into the next generation.

  • Example:


Create

Create

  • A new tree is created using initial population generation and added to the next generation.

  • Maintain genetic diversity.


Compress

Compress

  • Select a parent.

  • Select a subtree.

  • The part of the subtree up until a certain depth is defined as a new function.

  • The nodes below the level of the cut-off depth are considered as arguments to the module.

  • The module is named and added to the function set.

  • GP Parameters

    • Cut-off depth


Compress example

Compress: Example

Cut-off Depth = 1

Arity=2


Expand

Expand

  • Select a parent that contains a function node created by the compression operator.

  • Replace the function node with its corresponding subtree.


Expand example

Expand: Example


  • Login