Class DynamicATCS

  • All Implemented Interfaces:
    ConstructiveHeuristic<Permutation>

    public final class DynamicATCS
    extends WeightedShortestProcessingTime

    DynamicATCS is an implementation of a variation of the ATCS (Apparent Tardiness Cost with Setups) heuristic, which dynamically updates the average processing and setup times as it constructs the schedule. For an implementation of the original version of ATCS, without the dynamic parameter updates, see the ATCS class. ATCS is defined as: h(j) = (w[j]/p[j]) exp( -max(0,d[j] - T - p[j]) / (k1 p̄) ) exp( -s[i][j] / (k2 s̄)), where w[j] is the weight of job j, p[j] is its processing time, d[j] is the job's due date, T is the current time, and s[i][j] is any setup time of the job if it follows job i. The k1 and k2 are parameters that can be tuned based on problem instance characteristics, p̄ is the average processing time of remaining unscheduled jobs, and s̄ is the average setup time of the remaining unscheduled jobs. The authors of the ATCS heuristic simply computed p̄ and s̄ once at the start, while our implementation updates these dynamically along the way as jobs are scheduled.

    The constant MIN_H defines the minimum value the heuristic will return, preventing h(j)=0 in support of stochastic sampling algorithms for which h(j)=0 is problematic. This implementation returns max( MIN_H, h(j)), where MIN_H is a small non-zero value.

    • Field Detail

      • MIN_H

        public static final double MIN_H
        The minimum heuristic value. If the heuristic value as calculated is lower than MIN_H, then MIN_H is used as the heuristic value. The reason is related to the primary purpose of the constructive heuristics in the library: heuristic guidance for stochastic sampling algorithms, which assume positive heuristic values (e.g., an h of 0 would be problematic).
        See Also:
        Constant Field Values
    • Constructor Detail

      • DynamicATCS

        public DynamicATCS​(SingleMachineSchedulingProblem problem,
                           double k1,
                           double k2)
        Constructs an DynamicATCS heuristic.
        Parameters:
        problem - The instance of a scheduling problem that is the target of the heuristic.
        k1 - A parameter to the heuristic, which must be positive.
        k2 - A parameter to the heuristic, which must be positive.
        Throws:
        IllegalArgumentException - if problem.hasDueDates() returns false.
        IllegalArgumentException - if k ≤ 0.0.
      • DynamicATCS

        public DynamicATCS​(SingleMachineSchedulingProblem problem)
        Constructs an DynamicATCS heuristic. Sets the values of k1 and k2 according to the procedure described by the authors of the ATCS heuristic.
        Parameters:
        problem - The instance of a scheduling problem that is the target of the heuristic.
        Throws:
        IllegalArgumentException - if problem.hasDueDates() returns false.