Instructions for DGP Applet

Instructions


Back to DGP Applet page Buttons Windows GP Settings

Button Controls

The DGP applet allows you to control the genetic program and inspect the results.

Windows

The 'Santa Fe Trail' window :
The Fitnesses Window : When a complete generation has been evaluated, the Fitnesses window displays a histogram of the fitness values of all individuals.
The Status Window : The Status window indicates what is currently happening. Besides this, the fitnesses (hit counts/number of food pieces eaten) of the individuals (programs) sent to and received from the server are displayed when the applet sends and receives individuals from the server.
The Results Window : The Results window displays a symbolic representation of the best ant navigation program found so far, along with some other data.

GP Settings

You may inspect or change some parameters of the genetic program in the Settings dialog. Call it up with the Settings button.
Note that you cannot change the settings while the genetic program is running. Therefore, the Settings button is enabled only when the program is stopped.

Brief explanation of settings
Population size The number of individuals (i.e. programs) in the population. Each generation has the same number of individuals.
Max no. of generations in a run The maximum number of generations to be performed in a run.
Number of generations between migrations At an interval of a number of generations, the applet will connect to the server to do a migration whereby it exports a specified number of individuals to and imports a specified number of individuals from the server. This parameter defines this interval, in terms of the number of generations.
Number of individuals to export The number of individuals to export to the server during a migration.
Number of individuals to import The number of individuals to import from the server during a migration.
Max. depth for new individuals The maximum depth of program trees for new individuals.
Crossover fraction

Reproduction fraction

Mutation fraction

When producing a new generation, new individuals are generated from the old population by three methods:
  • crossover of two parents, producing two offsprings
  • reproduction of a single parent, producing one offspring
  • mutation of a single parent, producing one offspring

The ratio of the fraction numbers determines the ratio of the methods chosen.

Max. depth for individuals after crossover The maximum tree depth for programs produced by crossover. If an offspring exceeds this limit, one of the parents is chosen instead.
Max. depth for new subtrees in mutants The maximum depth of subtrees that are spliced in at mutation.
Method of generation Determines the shape of the program trees in the initial population:
  • Grow produces randomly bushy trees not exceeding a maximum depth. The distance from the root to the terminal nodes varies randomly.
  • Full produces fully balanced trees. The distance from the root to any terminal node is the same.
  • Ramped half and half is a mixture between the Grow and the Full method. Half of the trees are fully balanced and the other half is created bushy. The maximum depth varies between a minimum (typically 2) and the maximum value that you set with Max. depth for new individuals above.
Method of selection Determines the method how parents are selected when breeding a new generation:
  • Fitness proportionate prefers fitter individuals as parents. The fitter an individual, the more likely it is chosen as parent.
  • Tournament selects the fittest parent(s) out of a pool of randomly chosen individuals.
Elitism Specifies whether elitism is to be applied to the genetic program. With elitism, the best individual in the population of the current generation is always copied to the new population of the next generation to ensure that the best individual of a run is not lost through the generations.
Fitness cases For the Artificial Ant following the Santa Fe trail problem, there is only one fitness case. It is the Santa Fe trail which consists of 144 squares with 21 turns and 89 food units distributed non-uniformly along it.
Function set The list shows all the functions available. Functions are the internal nodes of the program trees.
The algorithm uses only those functions that you have selected in the list.
You must select at least one item.
Terminal set The list shows all the terminal types available. Terminals are the leaves of the program trees.
The algorithm uses only those terminals that you have selected in the list.
You must select at least one item.


This page has had hits since 24 August 1998.

Last updated on 24/08/98