ec.app.majority.func

Class If

java.lang.Object

ec.gp.GPNode

ec.app.majority.func.If

All Implemented Interfaces:

GPNodeParent, Prototype, Setup, Serializable, Cloneable

public class If
extends GPNode

See Also:

Serialized Form

Field Summary

Fields inherited from class ec.gp.GPNode

argposition, children, CHILDREN_UNKNOWN, constraints, GPNODEPRINTTAB, MAXPRINTBYTES, NODESEARCH_ALL, NODESEARCH_NONTERMINALS, NODESEARCH_TERMINALS, P_NODE, P_NODECONSTRAINTS, parent

Constructor Summary

Constructors

Constructor and Description
If()

Method Summary

Methods

Modifier and Type	Method and Description
void	eval(EvolutionState state, int thread, GPData input, ADFStack stack, GPIndividual individual, Problem problem) Evaluates the node with the given thread, state, individual, problem, and stack.
int	expectedChildren() Returns the number of children this node expects to have.
String	toString() Returns a Lisp-like atom for the node which can be read in again by computer.

Methods inherited from class ec.gp.GPNode

atDepth, checkConstraints, clone, cloneReplacing, cloneReplacing, cloneReplacing, cloneReplacingAtomic, cloneReplacingAtomic, cloneReplacingNoSubclone, constraints, contains, defaultBase, depth, errorInfo, iterator, iterator, iterator, lightClone, makeCTree, makeGraphvizSubtree, makeGraphvizTree, makeLatexTree, makeLispTree, makeLispTree, name, nodeEquals, nodeEquivalentTo, nodeHashCode, nodeInPosition, nodeInPosition, numNodes, numNodes, parentType, pathLength, printNode, printNode, printNode, printNodeForHumans, printNodeForHumans, printRootedTree, printRootedTree, printRootedTree, printRootedTreeForHumans, printRootedTreeForHumans, readNode, readNode, readRootedTree, readRootedTree, replaceWith, resetNode, rootedTreeEquals, rootedTreeHashCode, rootParent, setup, swapCompatibleWith, toStringForError, toStringForHumans, writeNode, writeRootedTree

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

If

public If()

Method Detail

toString

public String toString()

Description copied from class: GPNode

Returns a Lisp-like atom for the node which can be read in again by computer. If you need to encode an integer or a float or whatever for some reason (perhaps if it's an ERC), you should use the ec.util.Code library.

Specified by:

toString in class GPNode

expectedChildren

public int expectedChildren()

Description copied from class: GPNode

Returns the number of children this node expects to have. This method is only called by the default implementation of checkConstraints(...), and by default it returns CHILDREN_UNKNOWN. You can override this method to return a value >= 0, which will be checked for in the default checkConstraints(...), or you can leave this method alone and override checkConstraints(...) to check for more complex constraints as you see fit.

Overrides:

expectedChildren in class GPNode

eval

public void eval(EvolutionState state,
        int thread,
        GPData input,
        ADFStack stack,
        GPIndividual individual,
        Problem problem)

Description copied from class: GPNode

Evaluates the node with the given thread, state, individual, problem, and stack. Your random number generator will be state.random[thread]. The node should, as appropriate, evaluate child nodes with these same items passed to eval(...).

About input: input is special; it is how data is passed between parent and child nodes. If children "receive" data from their parent node when it evaluates them, they should receive this data stored in input. If (more likely) the parent "receives" results from its children, it should pass them an input object, which they'll fill out, then it should check this object for the returned value.

A tree is typically evaluated by dropping a GPData into the root. When the root returns, the resultant input should hold the return value.

In general, you should not be creating new GPDatas. If you think about it, in most conditions (excepting ADFs and ADMs) you can use and reuse input for most communications purposes between parents and children.

So, let's say that your GPNode function implements the boolean AND function, and expects its children to return return boolean values (as it does itself). You've implemented your GPData subclass to be, uh, BooleanData, which looks like

public class BooleanData extends GPData 
    {
    public boolean result;
    public GPData copyTo(GPData gpd)
      {
      ((BooleanData)gpd).result = result;
      }
    }

...so, you might implement your eval(...) function as follows:

public void eval(final EvolutionState state,
                     final int thread,
                     final GPData input,
                     final ADFStack stack,
                     final GPIndividual individual,
                     final Problem problem
    {
    BooleanData dat = (BooleanData)input;
    boolean x;

    // evaluate the first child
    children[0].eval(state,thread,input,stack,individual,problem);
  
    // store away its result
    x = dat.result;

    // evaluate the second child
    children[1].eval(state,thread,input,stack,individual,problem);

    // return (in input) the result of the two ANDed

    dat.result = dat.result && x;
    return;
    }
        

Specified by:

eval in class GPNode