source: branches/OKBJavaConnector/ECJClient/src/ec/gp/koza/MutationPipeline.java @ 12912

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


package ec.gp.koza;
import ec.*;
import ec.util.*;
import ec.gp.*;

/* 
 * MutationPipeline.java
 * 
 * Created: Tue Oct 12 18:50:56 1999
 * By: Sean Luke
 */

/**
 * MutationPipeline is a GPBreedingPipeline which 
 * implements a strongly-typed version of the 
 * "Point Mutation" operator as described in Koza I.
 * Actually, that's not quite true.  Koza doesn't have any tree depth restrictions
 * on his mutation operator.  This one does -- if the tree gets deeper than
 * the maximum tree depth, then the new subtree is rejected and another one is
 * tried.  Similar to how the Crosssover operator is implemented.
 *
 * <p>Mutated trees are restricted to being <tt>maxdepth</tt> depth at most.
 * If in <tt>tries</tt> attemptes, the pipeline cannot come up with a mutated
 * tree within the depth limit, then it simply copies the original individual
 * wholesale with no mutation.
 *
 * <p>One additional feature: if <tt>equal</tt> is true, then MutationPipeline
 * will attempt to replace the subtree with a tree of approximately equal size.
 * How this is done exactly, and how close it is, is entirely up to the pipeline's
 * tree builder -- for example, Grow/Full/HalfBuilder don't support this at all, while
 * RandomBranch will replace it with a tree of the same size or "slightly smaller"
 * as described in the algorithm.

 <p><b>Typical Number of Individuals Produced Per <tt>produce(...)</tt> call</b><br>
 ...as many as the child produces

 <p><b>Number of Sources</b><br>
 1

 <p><b>Parameters</b><br>
 <table>
 <tr><td valign=top><i>base</i>.<tt>tries</tt><br>
 <font size=-1>int &gt;= 1</font></td>
 <td valign=top>(number of times to try finding valid pairs of nodes)</td></tr>

 <tr><td valign=top><i>base</i>.<tt>maxdepth</tt><br>
 <font size=-1>int &gt;= 1</font></td>
 <td valign=top>(maximum valid depth of a crossed-over subtree)</td></tr>

 <tr><td valign=top><i>base</i>.<tt>ns</tt><br>
 <font size=-1>classname, inherits and != GPNodeSelector</font></td>
 <td valign=top>(GPNodeSelector for tree)</td></tr>

 <tr><td valign=top><i>base</i>.<tt>build</tt>.0<br>
 <font size=-1>classname, inherits and != GPNodeBuilder</font></td>
 <td valign=top>(GPNodeBuilder for new subtree)</td></tr>

 <tr><td valign=top><tt>equal</tt><br>
 <font size=-1>bool = <tt>true</tt> or <tt>false</tt> (default)</td>
 <td valign=top>(do we attempt to replace the subtree with a new one of roughly the same size?)</td></tr>

 <tr><td valign=top><i>base</i>.<tt>tree.0</tt><br>
 <font size=-1>0 &lt; int &lt; (num trees in individuals), if exists</font></td>
 <td valign=top>(tree chosen for mutation; if parameter doesn't exist, tree is picked at random)</td></tr>

 </table>

 <p><b>Default Base</b><br>
 gp.koza.mutate

 <p><b>Parameter bases</b><br>
 <table>

 <tr><td valign=top><i>base</i>.<tt>ns</tt><br>
 <td>nodeselect</td></tr>

 <tr><td valign=top><i>base</i>.<tt>build</tt><br>
 <td>builder</td></tr>

 </table>



 * @author Sean Luke
 * @version 1.0 
 */

public class MutationPipeline extends GPBreedingPipeline
    {
    public static final String P_NUM_TRIES = "tries";
    public static final String P_MAXDEPTH = "maxdepth";
    public static final String P_MUTATION = "mutate";
    public static final String P_BUILDER = "build";
    public static final String P_EQUALSIZE = "equal";
    public static final int INDS_PRODUCED = 1;
    public static final int NUM_SOURCES = 1;

    /** How the pipeline chooses a subtree to mutate */
    public GPNodeSelector nodeselect;

    /** How the pipeline builds a new subtree */
    public GPNodeBuilder builder;

    /** The number of times the pipeline tries to build a valid mutated
        tree before it gives up and just passes on the original */
    int numTries;
    
    /** The maximum depth of a mutated tree */
    int maxDepth;

    /** Do we try to replace the subtree with another of the same size? */
    boolean equalSize;

    /** Is our tree fixed?  If not, this is -1 */
    int tree;

    public Parameter defaultBase() { return GPKozaDefaults.base().push(P_MUTATION); }

    public int numSources() { return NUM_SOURCES; }

    public Object clone()
        {
        MutationPipeline c = (MutationPipeline)(super.clone());

        // deep-cloned stuff
        c.nodeselect = (GPNodeSelector)(nodeselect.clone());

        return c;
        }

    public void setup(final EvolutionState state, final Parameter base)
        {
        super.setup(state,base);
        
        Parameter def = defaultBase();
        Parameter p = base.push(P_NODESELECTOR).push(""+0);
        Parameter d = def.push(P_NODESELECTOR).push(""+0);

        nodeselect = (GPNodeSelector)
            (state.parameters.getInstanceForParameter(
                p,d, GPNodeSelector.class));
        nodeselect.setup(state,p);

        p = base.push(P_BUILDER).push(""+0);
        d = def.push(P_BUILDER).push(""+0);

        builder = (GPNodeBuilder)
            (state.parameters.getInstanceForParameter(
                p,d, GPNodeBuilder.class));
        builder.setup(state,p);

        numTries = state.parameters.getInt(
            base.push(P_NUM_TRIES),def.push(P_NUM_TRIES),1);
        if (numTries ==0)
            state.output.fatal("Mutation Pipeline has an invalid number of tries (it must be >= 1).",base.push(P_NUM_TRIES),def.push(P_NUM_TRIES));

        maxDepth = state.parameters.getInt(
            base.push(P_MAXDEPTH),def.push(P_MAXDEPTH),1);
        if (maxDepth==0)
            state.output.fatal("The Mutation Pipeline " + base + "has an invalid maximum depth (it must be >= 1).",base.push(P_MAXDEPTH),def.push(P_MAXDEPTH));

        equalSize = state.parameters.getBoolean(
            base.push(P_EQUALSIZE),def.push(P_EQUALSIZE),false);

        tree = TREE_UNFIXED;
        if (state.parameters.exists(base.push(P_TREE).push(""+0),
                def.push(P_TREE).push(""+0)))
            {
            tree = state.parameters.getInt(base.push(P_TREE).push(""+0),
                def.push(P_TREE).push(""+0),0);
            if (tree==-1)
                state.output.fatal("Tree fixed value, if defined, must be >= 0");
            }
        }


    /** Returns true if inner1 can feasibly be swapped into inner2's position */

    public boolean verifyPoints(GPNode inner1, GPNode inner2)
        {
        // We know they're swap-compatible since we generated inner1
        // to be exactly that.  So don't bother.

        // next check to see if inner1 can fit in inner2's spot
        if (inner1.depth()+inner2.atDepth() > maxDepth) return false;

        // checks done!
        return true;
        }




    public int produce(final int min, 
        final int max, 
        final int start,
        final int subpopulation,
        final Individual[] inds,
        final EvolutionState state,
        final int thread) 
        {
        // grab individuals from our source and stick 'em right into inds.
        // we'll modify them from there
        int n = sources[0].produce(min,max,start,subpopulation,inds,state,thread);

        // should we bother?
        if (!state.random[thread].nextBoolean(likelihood))
            return reproduce(n, start, subpopulation, inds, state, thread, false);  // DON'T produce children from source -- we already did


        GPInitializer initializer = ((GPInitializer)state.initializer);

        // now let's mutate 'em
        for(int q=start; q < n+start; q++)
            {
            GPIndividual i = (GPIndividual)inds[q];

            if (tree!=TREE_UNFIXED && (tree<0 || tree >= i.trees.length))
                // uh oh
                state.output.fatal("GP Mutation Pipeline attempted to fix tree.0 to a value which was out of bounds of the array of the individual's trees.  Check the pipeline's fixed tree values -- they may be negative or greater than the number of trees in an individual"); 
                

            int t;
            // pick random tree
            if (tree==TREE_UNFIXED)
                if (i.trees.length>1) t = state.random[thread].nextInt(i.trees.length);
                else t = 0;
            else t = tree;

            // validity result...
            boolean res = false;
            
            // prepare the nodeselector
            nodeselect.reset();
            
            // pick a node
            
            GPNode p1=null;  // the node we pick
            GPNode p2=null;
            
            for(int x=0;x<numTries;x++)
                {
                // pick a node in individual 1
                p1 = nodeselect.pickNode(state,subpopulation,thread,i,i.trees[t]);
                
                // generate a tree swap-compatible with p1's position
                
                
                int size = GPNodeBuilder.NOSIZEGIVEN;
                if (equalSize) size = p1.numNodes(GPNode.NODESEARCH_ALL);

                p2 = builder.newRootedTree(state,
                    p1.parentType(initializer),
                    thread,
                    p1.parent,
                    i.trees[t].constraints(initializer).functionset,
                    p1.argposition,
                    size);
                
                // check for depth and swap-compatibility limits
                res = verifyPoints(p2,p1);  // p2 can fit in p1's spot  -- the order is important!
                
                // did we get something that had both nodes verified?
                if (res) break;
                }
            
            GPIndividual j;

            if (sources[0] instanceof BreedingPipeline)
                // it's already a copy, so just smash the tree in
                {
                j=i;
                if (res)  // we're in business
                    {
                    p2.parent = p1.parent;
                    p2.argposition = p1.argposition;
                    if (p2.parent instanceof GPNode)
                        ((GPNode)(p2.parent)).children[p2.argposition] = p2;
                    else ((GPTree)(p2.parent)).child = p2;
                    j.evaluated = false;  // we've modified it
                    }
                }
            else // need to clone the individual
                {
                j = (GPIndividual)(i.lightClone());
                
                // Fill in various tree information that didn't get filled in there
                j.trees = new GPTree[i.trees.length];
                
                // at this point, p1 or p2, or both, may be null.
                // If not, swap one in.  Else just copy the parent.
                for(int x=0;x<j.trees.length;x++)
                    {
                    if (x==t && res)  // we've got a tree with a kicking cross position!
                        {
                        j.trees[x] = (GPTree)(i.trees[x].lightClone());
                        j.trees[x].owner = j;
                        j.trees[x].child = i.trees[x].child.cloneReplacingNoSubclone(p2,p1);
                        j.trees[x].child.parent = j.trees[x];
                        j.trees[x].child.argposition = 0;
                        j.evaluated = false; 
                        } // it's changed
                    else 
                        {
                        j.trees[x] = (GPTree)(i.trees[x].lightClone());
                        j.trees[x].owner = j;
                        j.trees[x].child = (GPNode)(i.trees[x].child.clone());
                        j.trees[x].child.parent = j.trees[x];
                        j.trees[x].child.argposition = 0;                   
                        }
                    }
                }
            
            // add the new individual, replacing its previous source
            inds[q] = j;
            }
        return n;
        }
    }