org.coinor.opents
Interface ObjectiveFunction

All Superinterfaces:
java.io.Serializable

public interface ObjectiveFunction
extends java.io.Serializable

The objective function is used to evaluate a Solution.

This code is licensed for public use under the Common Public License version 0.5.
The Common Public License, developed by IBM and modeled after their industry-friendly IBM Public License, differs from other common open source licenses in several important ways:

Copyright 2001 Robert Harder

Since:
1.0

Method Summary
 double[] evaluate(Solution soln, Move move)
          The TabuSearch expects an objective/ constraint penalties function to be able to evaluate a solution's worth.
 

Method Detail

evaluate

public double[] evaluate(Solution soln,
                         Move move)
The TabuSearch expects an objective/ constraint penalties function to be able to evaluate a solution's worth. The TabuSearch will pass the ObjectiveFunction a Solution and optionally pass a proposed Move. If the passed move is not null, then the evaluation should consider the effect that executing this move on the solution would have before evaluating it. If you can use some sort of incremental evaluation technique, this will save you time. If you must operate on the solution to actually calculate its value, you must return the solution to its original state before the method returns.

Casting example:


     public double[] evaluate( Solution soln, Move move )
{ MySolutionClass solution = (MySolutionClass) soln; // ... } // end evaluate

The array of returned values will later be compared lexicographically in the classic "goal-programming" style. If instead you want some goals to overpower higher goals, use the style of weighting the levels with appropriate values. Although all numbers are stored and calculated as doubles, they are cast to floats before being compared.

Be careful that you do not "reuse" arrays which can lead to different solutions sharing the same array of values in memory. A good technique is to evaluate your values as scalars and then return a fresh array like this:


     double val1 = ...;
     double val2 = ...;
     ...
     return new double[]{ val1, val2 };
 

Parameters:
soln - The solution to evaluate
move - If not null the proposed move
Returns:
The function's value.
Since:
1.0
See Also:
Solution, Move