DummyChromosome.java

package bsearch.representations;

import java.util.LinkedHashMap;

import org.nlogo.util.MersenneTwisterFast;

import bsearch.space.SearchSpace;

/**
 * A dummy Chromosome, it just acts as a container for a set of parameter-settings. 
 * Evolution algorithms should not use this Chromosome type for evolution --
 * it's just a convenient mechanism for representing a point in the search space 
 * (or potentially outside the bounds/resolution of the search space)
 * so it can be evaluated using the existing BatchModel running infrastructure.
 */
public strictfp class DummyChromosome implements Chromosome
{
	SearchSpace searchSpace;
	LinkedHashMap<String,Object> paramSettings;
	
	public DummyChromosome( SearchSpace searchSpace, LinkedHashMap<String,Object> paramSettings)
	{
		this.searchSpace = searchSpace;
		this.paramSettings = paramSettings;
	}	
  
	public LinkedHashMap<String,Object> getParamSettings()
	{
		return paramSettings;
	}
	
	@Override
	public DummyChromosome clone()
	{
		return new DummyChromosome(searchSpace,new LinkedHashMap<String,Object>(paramSettings));
	}
	
	public DummyChromosome mutate(double mutRate, MersenneTwisterFast rng)
	{
		throw new IllegalStateException("Can't evolve DummyChromosome!");
	}
	
	public Chromosome[] crossoverWith(Chromosome other, MersenneTwisterFast rng)
	{
		throw new IllegalStateException("Can't evolve DummyChromosome!");
	}

	/** Note: Depending on how the DummyChromosome was constructed, it may or may not
	 * represent a point in this search space.
	 */
	public SearchSpace getSearchSpace()
	{
		return searchSpace;
	}
    
	
	/**
	 * Redefine equality for DummyChromosomes.  
	 * Two chromosomes are considered equal if they represent the same parameter values. 
	 */
	public boolean equals(Object other)
	{
		if (other instanceof DummyChromosome)
		{
			DummyChromosome dc = (DummyChromosome) other;
			return paramSettings.equals(dc.paramSettings);
		}
		return false;
	}
	/**
	 * Reflects the redefined equals(Object) method, and it 
	 * should provide more efficient hashing for Chromosome keys in hashmaps.
	 */
	@Override
	public int hashCode()
	{
		int hashCode = 0;
		
		for (Object o: paramSettings.values())
		{
			hashCode = hashCode + o.hashCode(); 
		}
		return hashCode;
	}
}