Class: MHL::QPSOSwarm

Inherits:
GenericSwarmBehavior show all
Defined in:
lib/mhl/qpso_swarm.rb

Constant Summary

Constants inherited from GenericSwarmBehavior

GenericSwarmBehavior::DEFAULT_ALPHA, GenericSwarmBehavior::DEFAULT_C1, GenericSwarmBehavior::DEFAULT_C2, GenericSwarmBehavior::DEFAULT_CHI, GenericSwarmBehavior::PHI

Instance Method Summary collapse

Methods inherited from GenericSwarmBehavior

#update_attractor

Constructor Details

#initialize(size:, initial_positions:, alpha: nil, constraints: nil, logger: nil) ⇒ QPSOSwarm

Returns a new instance of QPSOSwarm.



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# File 'lib/mhl/qpso_swarm.rb', line 8

def initialize(size:, initial_positions:, alpha: nil, constraints: nil, logger: nil)
  @size      = size
  @particles = Array.new(@size) do |index|
    QuantumParticle.new(initial_positions[index])
  end

  # find problem dimension
  @dimension = initial_positions[0].size

  @iteration = 1

  # define procedure to get dynamic value for alpha
  @get_alpha = if alpha and alpha.respond_to? :call
    alpha
  else
    ->(it) { (alpha || DEFAULT_ALPHA).to_f }
  end

  @constraints = constraints
  @logger = logger

  if @constraints and @logger
    @logger.info "QPSOSwarm called w/ constraints: #{@constraints}"
  end
end

Instance Method Details

#mutate ⇒ Object 



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# File 'lib/mhl/qpso_swarm.rb', line 34

def mutate
  # get alpha parameter
  alpha = @get_alpha.call(@iteration)

  # this calculates the C_n parameter (the centroid of the set of all the
  # particle attractors) as defined in equations 4.81 and 4.82 of [SUN11].
  attractors = @particles.map {|p| p.attractor[:position] }
  c_n = 0.upto(@dimension-1).map do |j|
    attractors.inject(0.0) {|s,attr| s += attr[j] } / @size.to_f
  end

  # move particles
  @particles.each do |p|
    p.move(alpha, c_n, @swarm_attractor)
    if @constraints
      p.remain_within(@constraints)
    end
  end

  @iteration += 1
end