Package org.cicirello.search.problems.scheduling

Class WeightedFlowtime

java.lang.Object

org.cicirello.search.problems.scheduling.WeightedFlowtime

All Implemented Interfaces:

IntegerCostOptimizationProblem<Permutation>, Problem<Permutation>, SingleMachineSchedulingProblem

public final class WeightedFlowtime
extends Object
implements SingleMachineSchedulingProblem

Implements the scheduling cost function known as weighted flowtime. The flowtime F[j] of job j is: F[j] = C[j] - r[j], where C[j] is the time it is completed by the machine, and r[j] is its release time. The weighted flowtime cost function is the weighted sum over the jobs of: w[j]F[j], where w[j] is job j's weight.

Constructor Summary

Constructors

Constructor	Description
WeightedFlowtime(SingleMachineSchedulingProblemData instanceData)	Constructs a single machine scheduling problem for minimizing weighted flowtime.

Method Summary

Modifier and Type	Method	Description
int	cost(Permutation candidate)	Computes the cost of a candidate solution to the problem instance.
SingleMachineSchedulingProblemData	getInstanceData()	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.
int	minCost()	A lower bound on the minimum theoretical cost across all possible solutions to the problem instance, where lower cost implies better solution.
int	value(Permutation candidate)	Computes the value of the candidate solution within the usual constraints and interpretation of the problem.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.cicirello.search.problems.IntegerCostOptimizationProblem

getSolutionCostPair, isMinCost

Constructor Detail

WeightedFlowtime

public WeightedFlowtime(SingleMachineSchedulingProblemData instanceData)

Constructs a single machine scheduling problem for minimizing weighted flowtime.

Parameters:

instanceData - An encapsulation of the job characteristics, such as processing times, etc.

Method Detail

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.