public double Error(NeuralNetworkConfiguration configuration, double[][] trainDataVector, double[] position)
{
var squaredError = 0.0;
_configuration.NeuralNetwork.SetWeightsAndBiases(position);
var inputVector = new double[configuration.NumberOfInputNodes];
var expectedResult = new double[configuration.NumberOfOutputNodes];
foreach (var vector in trainDataVector)
{
Array.Copy(vector, inputVector, configuration.NumberOfInputNodes);
Array.Copy(vector, configuration.NumberOfInputNodes, expectedResult, 0, configuration.NumberOfOutputNodes);
var output = _configuration.NeuralNetwork.ComputeOutputs(inputVector);
for (var i = 0; i < output.Length; i++)
{
squaredError += ((output[i] - expectedResult[i]) * (output[i] - expectedResult[i]));
}
}
return squaredError / trainDataVector.Length;
}
private void UpdateParticleError(NeuralNetworkConfiguration configuration, double[][] dataVectors, Particle particle)
{
var newError = Error(configuration, dataVectors, particle.Properties.Position);
particle.ParticleError.Error = newError;
if (newError < particle.ParticleError.BestError)
{
var bestPosition = particle.Properties.BestPosition;
Array.Copy(particle.Properties.Position, particle.Properties.BestPosition, bestPosition.Length);
particle.ParticleError.BestError = newError;
}
if (!(newError < BestGlobalError))
return;
var position = particle.Properties.Position;
Array.Copy(particle.Properties.Position, BestGlobalPosition, position.Length);
BestGlobalError = newError;
}
private void StepTroughSwarm(NeuralNetworkConfiguration configuration, double[][] dataVectors)
{
var epoch = 0;
var randomizedParticles = NeuralNetworkHelpers.Randomize(_swarm.Length);
while (epoch < _configuration.MaxEpochs || BestGlobalError <= _configuration.ExitError)
{
if (epoch % 100 == 0)
Console.WriteLine("Epoch {0}. Best error = {1}", epoch, BestGlobalError);
for (var i = 0; i < _swarm.Length; i++)
{
var particle = _swarm[randomizedParticles[i]];
UpdatePositionAndVelocity(particle);
UpdateParticleError(configuration, dataVectors, particle);
LiveOrDie(particle, configuration, dataVectors);
}
epoch++;
}
}
private void LiveOrDie(Particle particle, NeuralNetworkConfiguration configuration, double[][] dataVectors)
{
var currentLifeProbability = _random.NextDouble();
if (!(currentLifeProbability < ParticleDeathProbability))
return;
var position = particle.Properties.Position;
for (var i = 0; i < position.Length; i++)
particle.Properties.Position[i] = (_configuration.DimensionMaximum - _configuration.DimensionMinimum) * _random.NextDouble() + _configuration.DimensionMinimum;
particle.ParticleError.Error = Error(configuration, dataVectors, particle.Properties.Position);
particle.ParticleError.BestError = particle.ParticleError.Error;
Array.Copy(particle.Properties.Position, particle.Properties.BestPosition,position.Length);
if (!(particle.ParticleError.Error < BestGlobalError))
return;
BestGlobalError = particle.ParticleError.Error;
var particlePosition = particle.Properties.Position;
Array.Copy(particle.Properties.Position, BestGlobalPosition, particlePosition.Length);
}
private void InitializeSwarm(NeuralNetworkConfiguration configuration, double[][] dataVectors)
{
for (int i = 0; i < _swarm.Length; i++)
{
CreateParticleForSwarm(configuration, dataVectors, i);
var localParticleError = _swarm[i].ParticleError;
if (localParticleError.Error < BestGlobalError)
{
var particlePosition = _swarm[i].Properties;
BestGlobalError = localParticleError.Error;
Array.Copy(particlePosition.Position, BestGlobalPosition, particlePosition.Position.Length);
}
}
}
private void CreateParticleForSwarm(NeuralNetworkConfiguration configuration, double[][] dataVectors, int i)
{
var properties = new ParticleProperties(_vectorSize);
var randomPosition = InitializeRandomPosition();
var error = Error(configuration, dataVectors, randomPosition);
var particleError = new ParticleError
{
Error = error,
BestError = error
};
var randomVelocity = InitializeRandomVelocity();
Array.Copy(randomPosition, properties.Position, randomPosition.Length);
Array.Copy(randomPosition, properties.BestPosition, randomPosition.Length);
Array.Copy(randomVelocity, properties.Velocity, randomVelocity.Length);
_swarm[i] = new Particle(particleError, properties);
}