java.lang.Object
org.cicirello.search.problems.TwoMaxEqualPeaks
 All Implemented Interfaces:
IntegerCostOptimizationProblem<BitVector>
,Problem<BitVector>
public final class TwoMaxEqualPeaks
extends Object
implements IntegerCostOptimizationProblem<BitVector>
This class implements a variation of the benchmarking problem known as TwoMax. The original
TwoMax problem was defined as a problem with one global optima (the vector of all 1bits) and a
suboptimal local optima (the vector of all 0bits). For an implementation of the original TwoMax
problem, see the
TwoMax
class. In the variation that we define here, we instead have two
equally desirable global optima (one of these is the vector of all 1bits, and the other is the
vector of all 0bits). We define it as follows. Maximize the function: f(x) =
20*CountOfOneBits(x)  10*n, where x is a vector of bits of length n. The two global optimal
solutions have a maximal value of 10*n. This search landscape has two basins of attraction, which
meet where the vector has an equal number of ones as zeros.
The value
method implements the maximization version as described above. The
algorithms of the ChipsnSalsa library are defined for minimization, requiring a cost function.
The cost
method implements the equivalent as the following minimization problem:
minimize cost(x) = 10*n  20*CountOfOneBits(x)  10*n. The global optima are still all 1bits
or all 0bits, each of which has a cost equal to 0.

Constructor Summary
ConstructorDescriptionConstructs a TwoMaxEqualPeaks object for use in evaluating candidate solutions to the TwoMaxEqualPeaks problem, a variation of the TwoMax problem but with two globally optimal solutions, rather than one global optima and a local optima. 
Method Summary
Modifier and TypeMethodDescriptionint
Computes the cost of a candidate solution to the problem instance.boolean
isMinCost
(int cost) Checks if a given cost value is equal to the minimum theoretical cost across all possible solutions to the problem instance, where lower cost implies better solution.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
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
costAsDouble, getSolutionCostPair

Constructor Details

TwoMaxEqualPeaks
public TwoMaxEqualPeaks()Constructs a TwoMaxEqualPeaks object for use in evaluating candidate solutions to the TwoMaxEqualPeaks problem, a variation of the TwoMax problem but with two globally optimal solutions, rather than one global optima and a local optima.


Method Details

cost
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 interfaceIntegerCostOptimizationProblem<BitVector>
 Parameters:
candidate
 The candidate solution to evaluate. Returns:
 The cost of the candidate solution. Lower cost means better 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 interfaceIntegerCostOptimizationProblem<BitVector>
 Returns:
 A lower bound on the minimum theoretical cost of the problem instance.

value
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 interfaceIntegerCostOptimizationProblem<BitVector>
 Parameters:
candidate
 The candidate solution to evaluate. Returns:
 The actual optimization value of the candidate solution.

isMinCost
public boolean isMinCost(int cost) Description copied from interface:IntegerCostOptimizationProblem
Checks if a given cost value is equal to the minimum theoretical cost across all possible solutions to the problem instance, where lower cost implies better solution. Specified by:
isMinCost
in interfaceIntegerCostOptimizationProblem<BitVector>
 Parameters:
cost
 The cost to check. Returns:
 true if cost is equal to the minimum theoretical cost,
