OSTRICH

The following optional group will configure a parallelized version of the PADDS algorithm and will be processed if ProgramType is set to “ParaPADDS”.

BeginParallelPADDSAlg
PerturbationValue      [r_val]
MaxIterations          [budget]
SelectionMetric        [metric]
EndParallelPADDSAlg

BeginParallelPADDSAlg
PerturbationValue      0.2
MaxIterations          50
SelectionMetric        Random
EndParallelPADDSAlg

Figure 1: General Format (left) and Example (right) of the parallel PADDS Group

Where BeginParallelPADDSAlg and EndParallelPADDSAlg are parsing tags that wrap the following set of algorithm configuration variables:

• PerturbationValue: This parameter defines the standard deviation of the decision variable perturbations as follows: PerturbationValue = StdDev / DV_Range. The allowable range is 0 to 1. As the value increases, the sampling becomes more and more spread out from the current best value of the decision variable. The default and recommended value is 0.2.
• MaxIterations: The computational budget in terms of the number of objective function evaluations. Users need to set this input for each problem according to how long each objective function evaluation takes and how quickly an answer is needed. The more objective functions you use, the better your estimate of the globally optimal solution will be. The default value is 50.

• SelectionMetric: This metric for scoring non-dominated solutions when seeding DDS trials within the overall PADDS algorithm. Values currently supported are listed below:

  • Random
  • CrowdingDistance
  • EstimatedHyperVolumeContribution
  • ExactHyperVolumeContribution

  The default selection metric value is “ExactHyperVolumeContribution”. For a discussion on choosing the appropriate selection metric see Asadzadeh and Tolson (2013).

Other acceptable parsing tags are:

• BeginParallelPADDS and EndParallelPADDS
• BeginParaPADDSAlg and EndParaPADDSAlg
• BeginParaPADDS and EndParaPADDS
• BeginPADDSAlg and EndPADDSAlg
• BeginPADDS and EndPADDS