/// <summary>
/// Runs learning epoch.
/// </summary>
///
/// <param name="input">Array of input vectors.</param>
/// <param name="output">Array of output vectors.</param>
///
/// <returns>Returns summary squared learning error for the entire epoch.</returns>
///
/// <remarks><para><note>While running the neural network's learning process, it is required to
/// pass the same <paramref name="input"/> and <paramref name="output"/> values for each
/// epoch. On the very first run of the method it will initialize evolutionary fitness
/// function with the given input/output. So, changing input/output in middle of the learning
/// process, will break it.</note></para></remarks>
///
public double RunEpoch( double[][] input, double[][] output )
{
Debug.Assert( input.Length > 0 );
Debug.Assert( output.Length > 0 );
Debug.Assert( input.Length == output.Length );
Debug.Assert( network.InputsCount == input.Length );
// check if it is a first run and create population if so
if ( population == null )
{
// sample chromosome
DoubleArrayChromosome chromosomeExample = new DoubleArrayChromosome(
chromosomeGenerator, mutationMultiplierGenerator, mutationAdditionGenerator,
numberOfNetworksWeights );
// create population ...
population = new Population( populationSize, chromosomeExample,
new EvolutionaryFitness( network, input, output ), selectionMethod );
// ... and configure it
population.CrossoverRate = crossOverRate;
population.MutationRate = mutationRate;
population.RandomSelectionPortion = randomSelectionRate;
}
// run genetic epoch
population.RunEpoch( );
// get best chromosome of the population
DoubleArrayChromosome chromosome = (DoubleArrayChromosome) population.BestChromosome;
double[] chromosomeGenes = chromosome.Value;
// put best chromosome's value into neural network's weights
int v = 0;
for ( int i = 0; i < network.Layers.Length; i++ )
{
Layer layer = network.Layers[i];
for ( int j = 0; j < layer.Neurons.Length; j++ )
{
ActivationNeuron neuron = layer.Neurons[j] as ActivationNeuron;
for ( int k = 0; k < neuron.Weights.Length; k++ )
{
neuron.Weights[k] = chromosomeGenes[v++];
}
neuron.Threshold = chromosomeGenes[v++];
}
}
Debug.Assert( v == numberOfNetworksWeights );
return 1.0 / chromosome.Fitness;
}
/// <summary>
/// Perform migration between two populations.
/// </summary>
///
/// <param name="anotherPopulation">Population to do migration with.</param>
/// <param name="numberOfMigrants">Number of chromosomes from each population to migrate.</param>
/// <param name="migrantsSelector">Selection algorithm used to select chromosomes to migrate.</param>
///
/// <remarks><para>The method performs migration between two populations - current and the
/// <paramref name="anotherPopulation">specified one</paramref>. During migration
/// <paramref name="numberOfMigrants">specified number</paramref> of chromosomes is choosen from
/// each population using <paramref name="migrantsSelector">specified selection algorithms</paramref>
/// and put into another population replacing worst members there.</para></remarks>
///
public void Migrate( Population anotherPopulation, int numberOfMigrants, ISelectionMethod migrantsSelector )
{
int currentSize = this.size;
int anotherSize = anotherPopulation.Size;
// create copy of current population
List<IChromosome> currentCopy = new List<IChromosome>( );
for ( int i = 0; i < currentSize; i++ )
{
currentCopy.Add( population[i].Clone( ) );
}
// create copy of another population
List<IChromosome> anotherCopy = new List<IChromosome>( );
for ( int i = 0; i < anotherSize; i++ )
{
anotherCopy.Add( anotherPopulation.population[i].Clone( ) );
}
// apply selection to both populations' copies - select members to migrate
migrantsSelector.ApplySelection( currentCopy, numberOfMigrants );
migrantsSelector.ApplySelection( anotherCopy, numberOfMigrants );
// sort original populations, so the best chromosomes are in the beginning
population.Sort( );
anotherPopulation.population.Sort( );
// remove worst chromosomes from both populations to free space for new members
population.RemoveRange( currentSize - numberOfMigrants, numberOfMigrants );
anotherPopulation.population.RemoveRange( anotherSize - numberOfMigrants, numberOfMigrants );
// put migrants to corresponding populations
population.AddRange( anotherCopy );
anotherPopulation.population.AddRange( currentCopy );
// find best chromosomes in each population
FindBestChromosome( );
anotherPopulation.FindBestChromosome( );
}