/**
* 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 velocity, position and personal
/// best position of a particle.
/// </summary>
/// <param name="particleIndex">index of the particle in the swarm</param>
/// <param name="init">if true, the position and velocity
/// will be initialised. </param>
public void UpdateParticle(int particleIndex, bool init)
{
int i = particleIndex;
double[] particlePosition = null;
if (init)
{
// Create a new particle with random values.
// Except the first particle which has the same values
// as the network passed to the algorithm.
if (m_networks[i] == null)
{
m_networks[i] = (BasicNetwork)m_bestNetwork.Clone();
if (i > 0)
{
m_randomizer.Randomize(m_networks[i]);
}
}
particlePosition = GetNetworkState(i);
m_bestVectors[i] = particlePosition;
// randomise the velocity
m_va.Randomise(m_velocities[i], m_maxVelocity);
}
else
{
particlePosition = GetNetworkState(i);
UpdateVelocity(i, particlePosition);
// velocity clamping
m_va.ClampComponents(m_velocities[i], m_maxVelocity);
// new position (Xt = Xt-1 + Vt)
m_va.Add(particlePosition, m_velocities[i]);
// pin the particle against the boundary of the search space.
// (only for the components exceeding maxPosition)
m_va.ClampComponents(particlePosition, m_maxPosition);
SetNetworkState(i, particlePosition);
}
UpdatePersonalBestPosition(i, particlePosition);
}
/// <summary>
/// Update the velocity, position and personal
/// best position of a particle.
/// </summary>
/// <param name="particleIndex">index of the particle in the swarm</param>
protected void UpdateParticle(int particleIndex)
{
double[] particlePosition = _particles[particleIndex].LongTermMemory;
UpdateVelocity(particleIndex);
// velocity clamping
VectorAlgebra.ClampComponents(_velocities[particleIndex], maxVelocity);
// new position (Xt = Xt-1 + Vt)
VectorAlgebra.Add(particlePosition, _velocities[particleIndex]);
// pin the particle against the boundary of the search space.
// (only for the components exceeding maxPosition)
VectorAlgebra.ClampComponents(particlePosition, maxPosition);
UpdatePersonalBestPosition(particleIndex, particlePosition);
}