Module org.cicirello.chips_n_salsa
Package org.cicirello.search.problems.scheduling

Class MinimizeMakespan

java.lang.Object
org.cicirello.search.problems.scheduling.MinimizeMakespan
All Implemented Interfaces:
IntegerCostOptimizationProblem<Permutation>, Problem<Permutation>, SingleMachineSchedulingProblem
public final class MinimizeMakespan extends Object implements SingleMachineSchedulingProblem
Implements the common scheduling cost function known as makespan. The makespan of a schedule is equal to the completion time of the last job in the schedule. If the problem doesn't have release dates and setup times, then minimizing makespan is trivial since all possible permutations of the jobs has a makespan simply equal to the sum of the process times. If the problem has sequence-dependent setups, then minimizing makespan is NP-Hard and is roughly equivalent to the wandering salesperson problem.

  • Constructor Details

    • MinimizeMakespan

      public MinimizeMakespan(SingleMachineSchedulingProblemData instanceData)
      Constructs a single machine scheduling problem for minimizing makespan.
      Parameters:
      instanceData - An encapsulation of the job characteristics, such as processing times, etc.

  • Method Details

    • getInstanceData

      public SingleMachineSchedulingProblemData getInstanceData()
      Description copied from interface: SingleMachineSchedulingProblem
      Gets an object that encapsulates the data describing the scheduling problem instance, such as number of jobs, and the characteristics of the jobs, such as processing times, setup times, due dates, weights, etc.
      Specified by:
      getInstanceData in interface SingleMachineSchedulingProblem
      Returns:
      an encapsulation of the data describing the scheduling problem instance

    • cost

      public int cost(Permutation candidate)
      Description copied from interface: IntegerCostOptimizationProblem
      Computes the cost of a candidate solution to the problem instance. The lower the cost, the more optimal the candidate solution.
      Specified by:
      cost in interface IntegerCostOptimizationProblem<Permutation>
      Parameters:
      candidate - The candidate solution to evaluate.
      Returns:
      The cost of the candidate solution. Lower cost means better solution.

    • value

      public int value(Permutation candidate)
      Description copied from interface: IntegerCostOptimizationProblem
      Computes the value of the candidate solution within the usual constraints and interpretation of the problem.
      Specified by:
      value in interface IntegerCostOptimizationProblem<Permutation>
      Parameters:
      candidate - The candidate solution to evaluate.
      Returns:
      The actual optimization value of the candidate solution.

    • minCost

      public int minCost()
      Description copied from interface: IntegerCostOptimizationProblem
      A lower bound on the minimum theoretical cost across all possible solutions to the problem instance, where lower cost implies better solution. The default implementation returns Integer.MIN_VALUE.
      Specified by:
      minCost in interface IntegerCostOptimizationProblem<Permutation>
      Returns:
      A lower bound on the minimum theoretical cost of the problem instance.