/*
  Copyright 2006 by Sean Luke
  Licensed under the Academic Free License version 3.0
  See the file "LICENSE" for more information
*/


package ec.app.parity;
import ec.util.*;
import ec.*;
import ec.gp.*;
import ec.gp.koza.*;
import ec.simple.*;

/* 
 * Parity.java
 * 
 * Created: Mon Nov  1 15:46:19 1999
 * By: Sean Luke
 */

/**
 * Parity implements the family of n-[even|odd]-Parity problems up 
 * to 32-parity.  Read the README file in this package for information on
 * how to set up the parameter files to your liking -- it's a big family.
 *
 * 
The Parity family evolves a boolean function on n sets of bits,
 * which returns true if the number of 1's is even (for even-parity) or odd
 * (for odd-parity), false otherwise. 
 *
 
Parameters

 

 
base.data

 classname, inherits or == ec.app.parity.ParityData
 
(the class for the prototypical GPData object for the Parity problem)
 
base.even

  bool = true (default) or false
 
(is this even-parity (as opposed to odd-parity)?)
 
base.bits

  2 >= int <= 31
 
(The number of data bits)
 

 
Parameter bases

 

 
base.data
 
species (the GPData object)
 
 *
 * @author Sean Luke
 * @version 1.0 
 */

public class Parity extends GPProblem implements SimpleProblemForm
    {
    private static final long serialVersionUID = 1;

    public static final String P_NUMBITS = "bits";
    public static final String P_EVEN = "even";

    public boolean doEven;
    public int numBits;
    public int totalSize;

    public int bits;  // data bits

    public void setup(final EvolutionState state,
        final Parameter base)
        {
        // very important, remember this
        super.setup(state,base);

        // not using a default base here

        // verify our input is the right class (or subclasses from it)
        if (!(input instanceof ParityData))
            state.output.fatal("GPData class must subclass from " + ParityData.class,
                base.push(P_DATA), null);

        // can't use all 32 bits -- Java is signed.  Must use 31 bits.        
        numBits = state.parameters.getIntWithMax(base.push(P_NUMBITS),null,2,31);
        if (numBits<2)
            state.output.fatal("The number of bits for Parity must be between 2 and 31 inclusive",base.push(P_NUMBITS));
        
        totalSize = 1;
        for(int x=0;x>> b) & 1;
                tb &= 1;  // now tb is 1 if we're odd, 0 if we're even

                ((GPIndividual)ind).trees[0].child.eval(
                    state,threadnum,input,stack,((GPIndividual)ind),this);

                if ((doEven && ((input.x & 1) != tb)) ||
                    ((!doEven) && ((input.x & 1) == tb)))
                    sum++;
                }
                
            // the fitness better be KozaFitness!
            KozaFitness f = ((KozaFitness)ind.fitness);
            f.setStandardizedFitness(state, (totalSize - sum));
            f.hits = sum;
            ind.evaluated = true;
            }
        }
    }