/*
  Copyright 2012 by Sean Luke
  Licensed under the Academic Free License version 3.0
  See the file "LICENSE" for more information
*/


package ec.app.regression.func;
import ec.*;
import ec.app.regression.*;
import ec.gp.*;
import ec.util.*;
import java.io.*;


/* 
 * VladERCA.java
 * 
 * Created: Wed Nov  3 18:26:37 1999
 * By: Sean Luke

 
This ERC appears all three the Vladislavleva function sets.  It is not a constant but rather a function of one parameter (n) with an internal constant (c) and returns n^c.  Note that the value of c is drawn from the fully-closed range [-5.0, 5.0].

 
E. Vladislavleva, G. Smits, and D. Den Hertog. Order of Nonlinearity as a Complexity Measure for Models Generated by Symbolic Regression via Pareto Genetic Programming. IEEE Trans EC, 13(2):333-349, 2009.
*/


/**
 * @author Sean Luke
 * @version 1.0 
 */

public class VladERCA extends RegERC
    {
    public String name() { return "VladERCA"; }
    public int expectedChildren() { return 1; }

    public void resetNode(final EvolutionState state, final int thread)
        {
        value = state.random[thread].nextDouble(true, true) * 5.0;
        }

    public String toStringForHumans()
        { return "n^" + value; }

    public void eval(final EvolutionState state,
        final int thread,
        final GPData input,
        final ADFStack stack,
        final GPIndividual individual,
        final Problem problem)
        {
        RegressionData rd = ((RegressionData)(input));

        children[0].eval(state,thread,input,stack,individual,problem);
        rd.x = Math.pow(rd.x, value);
        }

    }