Add compatibility threshold adjustment.

README.md

@@ -120,14 +120,16 @@ The following is the default configuration of TinyNEAT. For any changes, for exa
 ```js
 // Closely based on parameters of the original NEAT paper
 export const defaultConfig = {
-	initialPopulationSize: 150, // Number of networks in the population
+	initialPopulationSize: 50, // Number of networks in the population
+	targetSpecies: 10, // Desired number of species to maintain
 	maxGenerations: 100, // Stopping point for evolution
 
 	maximumStagnation: 15, // Maximum number of generations a species is allowed to stay the same fitness before it is removed
-	excessCoefficient: 1.0, // Coefficient representing how important excess genes are in measuring compatibility
-	disjointCoefficient: 1.0, // Coefficient for disjoint genes
-	weightDifferenceCoefficient: 0.4, // Coefficient for average weight difference (highly recommended for tuning)
-	compatibilityThreshold: 3.0, // Threshold for speciation (highly recommended for tuning)
+	excessCoefficient: 2.0, // Coefficient representing how important excess genes are in measuring compatibility
+	disjointCoefficient: 2.0, // Coefficient for disjoint genes
+	weightDifferenceCoefficient: 1.0, // Coefficient for average weight difference (highly recommended for tuning)
+	compatibilityThreshold: 6.0, // Threshold for speciation (highly recommended for tuning)
+	compatibilityModifier: 0.3, // Rate to change the compatibility threshold at when target species count is not met
 	survivalThreshold: 0.2, // Percentage of each species allowed to reproduce
 	mutateOnlyProbability: 0.25, // Probability that a reproduction will only result from mutation and not crossover
 	mateOnlyProbability: 0.2, // Probability an offspring will be created only through crossover without mutation
@@ -139,15 +141,15 @@ export const defaultConfig = {
 	mateByAveragingProbability: 0.4, // Probability that matching genes will be averaged during crossover
 	reenableConnectionProbability: 0.01, // Probability that a connection is randomly reenabled during crossover
 
-	fitnessSort: "max", // Whether a higher or a lower fitness is better
+	fitnessSort: "max",
 
 	largeNetworkSize: 20, // A network with this many genes is considered to be large
-	minimumSpeciesSize: 2, // The minimum number of offspring a species can have
+	minimumSpeciesSize: 1, // The minimum number of offspring a species can have
 
 	hallOfFameSize: 10, // The number of top-performing individuals to store
 
-	inputSize: 3, // The number of inputs to each neural network
-	outputSize: 2, // The number of outputs of each neural network
+	inputSize: 1, // The number of inputs to each neural network
+	outputSize: 1, // The number of outputs of each neural network
 
 	// Plugin for the specific type of neural network (ANN, RNN, etc)
 	nnPlugin: ANNPlugin(),

examples/racing/sketch.js

@@ -24,7 +24,7 @@ const tn = TinyNEAT({
 	initialPopulationSize: POPULATION_SIZE,
 	inputSize: 16,
 	outputSize: 1,
-	compatibilityThreshold: 2.0,
+	compatibilityThreshold: 6.0,
 	addLinkProbability: 0.1,
 	addNodeProbability: 0.2,
 	mutateWeightProbability: 0.4,

src/config.ts

@@ -5,14 +5,16 @@ export type FitnessSort = "max" | "min"
 
 // Closely based on parameters of the original NEAT paper
 export const defaultConfig = {
-	initialPopulationSize: 150, // Number of networks in the population
+	initialPopulationSize: 50, // Number of networks in the population
+	targetSpecies: 10, // Desired number of species to maintain
 	maxGenerations: 100, // Stopping point for evolution
 
 	maximumStagnation: 15, // Maximum number of generations a species is allowed to stay the same fitness before it is removed
-	excessCoefficient: 1.0, // Coefficient representing how important excess genes are in measuring compatibility
-	disjointCoefficient: 1.0, // Coefficient for disjoint genes
-	weightDifferenceCoefficient: 0.4, // Coefficient for average weight difference (highly recommended for tuning)
-	compatibilityThreshold: 3.0, // Threshold for speciation (highly recommended for tuning)
+	excessCoefficient: 2.0, // Coefficient representing how important excess genes are in measuring compatibility
+	disjointCoefficient: 2.0, // Coefficient for disjoint genes
+	weightDifferenceCoefficient: 1.0, // Coefficient for average weight difference (highly recommended for tuning)
+	compatibilityThreshold: 6.0, // Threshold for speciation (highly recommended for tuning)
+	compatibilityModifier: 0.3, // Rate to change the compatibility threshold at when target species count is not met
 	survivalThreshold: 0.2, // Percentage of each species allowed to reproduce
 	mutateOnlyProbability: 0.25, // Probability that a reproduction will only result from mutation and not crossover
 	mateOnlyProbability: 0.2, // Probability an offspring will be created only through crossover without mutation
@@ -27,12 +29,12 @@ export const defaultConfig = {
 	fitnessSort: <FitnessSort>"max",
 
 	largeNetworkSize: 20, // A network with this many genes is considered to be large
-	minimumSpeciesSize: 2, // The minimum number of offspring a species can have
+	minimumSpeciesSize: 1, // The minimum number of offspring a species can have
 
 	hallOfFameSize: 10, // The number of top-performing individuals to store
 
-	inputSize: 3, // The number of inputs to each neural network
-	outputSize: 2, // The number of outputs of each neural network
+	inputSize: 1, // The number of inputs to each neural network
+	outputSize: 1, // The number of outputs of each neural network
 
 	// Plugin for the specific type of neural network (ANN, RNN, etc)
 	nnPlugin: ANNPlugin(),

src/evolve.ts

@@ -21,6 +21,9 @@ export const evolvePopulation = (
 	// Separate the current population into species
 	speciatePopulation(population, species, config)
 
+	// Adjust the compatibility threshold based on the number of species
+	adjustCompatibilityThreshold(species, config)
+
 	// Adjust the fitness of each organism to normalize based on species size
 	calculateAdjustedFitnesses(species)
 
@@ -160,3 +163,16 @@ const allocateOffspring = (population: Genome[], species: Genome[][]) => {
 		Math.round((averageFitness / totalAverageFitness) * population.length),
 	)
 }
+
+const adjustCompatibilityThreshold = (species: Genome[][], config: Config) => {
+	// Modify the compatibility threshold to dynamically control the number of species
+	if (species.length < config.targetSpecies) {
+		config.compatibilityThreshold -= config.compatibilityModifier
+	} else if (species.length > config.targetSpecies) {
+		config.compatibilityThreshold += config.compatibilityModifier
+	}
+
+	// Prevent the compatibility threshold from getting too small
+	if (config.compatibilityThreshold < config.compatibilityModifier)
+		config.compatibilityThreshold = config.compatibilityModifier
+}