toxgene.core.random.ToxGeometric Maven / Gradle / Ivy

Go to download
/**
 * Implements a random generator for geometric probability distributions
 *
 * @author Denilson Barbosa
 * @version 0.1
 */

package toxgene.core.random;


import java.util.Random;
import toxgene.core.ToXgeneErrorException;
import toxgene.core.genes.CreateGeneException;

public class ToxGeometric implements ToxRandom{
  private float min, max, p;
  private Random rand;

  public ToxGeometric(float min, float max, float P, long seed){
		this.min = min;
		this.max = max;
		this.p = 1 - (max-min/P+(max-min));

		if (max < min){
			throw new CreateGeneException("invalid min and max values for "+
																		"ToxGeometric random generator!");
		}

		if (P < min || P > max){
			throw new CreateGeneException("invalid mean value for "+
																		"ToxGeometric random generator!");
		}

		rand = new Random(seed);
  }

  public long nextInt(){
		return (Math.round((double)nextFloat()));
  }

  public float nextFloat(){
		float U = rand.nextFloat();
		float result = (float)(Math.log(U)/Math.log(p));

		//check for consistency
		if (result < min)
			result = min;
		if (result > max)
			result = max;

		return result;
  }

  public float minValue(){
		return min;
  }

  public float maxValue(){
		return max;
  }

  public long nextInt(float value){
		//in some cases we call this function with the max_value as parameter :(
		if (value == max)
			return ((long)nextFloat());

		if (value < min){
			throw new ToXgeneErrorException("cannot update distribution max value: "+
																			value+" is smaller than minimum value: "+
																			min);
		}
	
		return (Math.round((double)min + ((value-min) * nextFloat())));
  }
}