Configuration file format

The configuration file is in the format described in the Python ConfigParser documentation. Currently, all values must be explicitly enumerated in the configuration file. This makes it less likely that code changes will result in your project silently using different NEAT settings.

[phenotype] section

• input_nodes

  The number of nodes through which the network receives input.

• hidden_nodes

  The number of hidden nodes to add to each genome in the initial population.

• output_nodes

  The number of nodes to which the network delivers output.

• initial_connection

  Specifies the initial connectivity of newly-created genomes. There are three allowed values:

  • unconnected - No connection genes are initially present.
  • fs_neat - One connection gene from one input to all hidden and output genes. (This is the FS-NEAT scheme.)
  • fully_connected - Each input gene is connected to all hidden and output genes, and each hidden gene is connected to all output genes.

• max_weight, min_weight

  Connection weights (as well as node bias and response) will be limited to this range.

• feedforward

  If this evaluates to True, generated networks will not be allowed to have recurrent connections. Otherwise they may be (but are not forced to be) recurrent.

• activation_functions

  A space-separated list of the activation functions that may be used in constructing networks. Allowable values are: abs, clamped, exp, gauss, hat, identity, inv, log, relu, sigmoid, sin, and tanh. The implementation of these functions can be found in the nn module.

• weight_stdev

  The standard deviation of the zero-centered normal distribution used to generate initial and replacement weights.

[genetic] section

• pop_size

  The number of individuals in each generation.

• max_fitness_threshold

  When at least one individual’s measured fitness exceeds this threshold, the evolution process will terminate.

• prob_add_conn

  The probability that mutation will add a connection between existing nodes. Valid values are on [0.0, 1.0].

• prob_add_node

  The probability that mutation will add a new hidden node into an existing connection. Valid values are on [0.0, 1.0].

• prob_delete_conn

  The probability that mutation will delete an existing connection. Valid values are on [0.0, 1.0].

• prob_delete_node

  The probability that mutation will delete an existing hidden node and any connections to it. Valid values are on [0.0, 1.0].

• prob_mutate_bias

  The probability that mutation will change the bias of a node by adding a random value.

• bias_mutation_power

  The standard deviation of the zero-centered normal distribution from which a bias change is drawn.

• prob_mutate_response

  The probability that mutation will change the response of a node by adding a random value.

• response_mutation_power

  The standard deviation of the zero-centered normal distribution from which a response change is drawn.

• prob_mutate_weight

  The probability that mutation will change the weight of a connection by adding a random value.

• prob_mutate_activation

  The probability that mutation will change the activation function of a hidden or output node.

• prob_replace_weight

  The probability that mutation will replace the weight of a connection with a new random value.

• weight_mutation_power

  The standard deviation of the zero-centered normal distribution from which a weight change is drawn.

• prob_toggle_link

  The probability that the enabled status of a connection will be toggled.

• elitism

  The number of most fit individuals in each species that will be preserved as-is from one generation to the next.

• reset_on_extinction

  If this evalutes to True, when all species simultaneously become extinct due to stagnation, a new random population will be created. If False, a CompleteExtinctionException will be thrown.

[genotype compatibility] section

• compatibility_threshold

  Individuals whose genomic distance is less than this threshold are considered to be in the same species.

• excess_coefficient

  The coefficient for the excess gene count’s contribution to the genomic distance.

• disjoint_coefficient

  The coefficient for the disjoint gene count’s contribution to the genomic distance.

• weight_coefficient

  The coefficient for the average weight difference’s contribution to the genomic distance.

[species] section

• survival_threshold

  The fraction for each species allowed to reproduce on each generation.

• max_stagnation

  Species that have not shown improvement in more than this number of generations will be considered stagnant and removed.