/// <summary>
/// Update the velocity of a particle
/// </summary>
/// <param name="particleIndex">index of the particle in the swarm</param>
/// <param name="particlePosition">the particle current position vector</param>
protected void UpdateVelocity(int particleIndex, double[] particlePosition)
{
int i = particleIndex;
double[] vtmp = new double[particlePosition.Length];
// Standard PSO formula
// inertia weight
m_va.Mul(m_velocities[i], m_inertiaWeight);
// cognitive term
m_va.Copy(vtmp, m_bestVectors[i]);
m_va.Sub(vtmp, particlePosition);
m_va.MulRand(vtmp, m_c1);
m_va.Add(m_velocities[i], vtmp);
// social term
if (i != m_bestVectorIndex)
{
m_va.Copy(vtmp, m_pseudoAsynchronousUpdate ? m_bestVectors[m_bestVectorIndex] : m_bestVector);
m_va.Sub(vtmp, particlePosition);
m_va.MulRand(vtmp, m_c2);
m_va.Add(m_velocities[i], vtmp);
}
}
/**
* Update the velocity of a particle
*
* @param particleIndex index of the particle in the swarm
*/
protected void UpdateVelocity(int particleIndex)
{
double[] particlePosition = _particles[particleIndex].LongTermMemory;
double[] vtmp = new double[particlePosition.Length];
// Standard PSO formula
// inertia weight
VectorAlgebra.Mul(_velocities[particleIndex], inertiaWeight);
// cognitive term
VectorAlgebra.Copy(vtmp, _bestVectors[particleIndex]);
VectorAlgebra.Sub(vtmp, particlePosition);
VectorAlgebra.MulRand(_rnd, vtmp, this.c1);
VectorAlgebra.Add(_velocities[particleIndex], vtmp);
// social term
if (particleIndex != _bestVectorIndex)
{
VectorAlgebra.Copy(vtmp, _bestVector);
VectorAlgebra.Sub(vtmp, particlePosition);
VectorAlgebra.MulRand(_rnd, vtmp, c2);
VectorAlgebra.Add(_velocities[particleIndex], vtmp);
}
}
/// <summary>
/// Update the personal best position of a particle.
/// </summary>
/// <param name="particleIndex">Index of the particle in the swarm.</param>
/// <param name="particlePosition">the particle current position vector.</param>
protected void UpdatePersonalBestPosition(int particleIndex, double[] particlePosition)
{
// set the network weights and biases from the vector
double score = _score.CalculateScore(_particles[particleIndex]);
// update the best vectors (g and i)
if ((_bestScores[particleIndex] == 0) || IsScoreBetter(score, _bestScores[particleIndex]))
{
_bestScores[particleIndex] = score;
VectorAlgebra.Copy(_bestVectors[particleIndex], particlePosition);
}
}
/// <summary>
/// Update the swarm's best position.
/// </summary>
protected void UpdateGlobalBestPosition()
{
bool bestUpdated = false;
for (int i = 0; i < this._particles.Length; i++)
{
if ((_bestVectorIndex == -1) || IsScoreBetter(_bestScores[i], _bestScores[_bestVectorIndex]))
{
_bestVectorIndex = i;
bestUpdated = true;
}
}
if (bestUpdated)
{
VectorAlgebra.Copy(_bestVector, _bestVectors[_bestVectorIndex]);
this.bestScore = _bestScores[_bestVectorIndex];
}
}