Example file

eo/test/t-eoSymreg.cpp

@@ -0,0 +1,276 @@
+#pragma warning(disable:4786)
+
+#include "eoParseTree.h"
+#include "eoEvalFunc.h"
+
+using namespace gp_parse_tree;
+using namespace std;
+
+//-----------------------------------------------------------------------------
+
+class SymregNode
+{
+public :
+
+	enum Operator {X = 'x', Plus = '+', Min = '-', Mult = '*', PDiv = '/'};
+
+	SymregNode(void)				{ init(); }
+	SymregNode(Operator _op)		{ op = _op; }
+	virtual ~SymregNode(void)			{}
+
+	// arity function
+	int arity(void) const      { return op == X? 0 : 2; }
+	
+	// evaluation function, single case, using first argument to give value of variable
+	template <class Children>
+	double operator()(double var, Children args) const
+	{
+		switch (op)
+		{
+		case Plus : return args[0].apply(var) + args[1].apply(var);
+		case Min  : return args[0].apply(var) - args[1].apply(var);
+		case Mult : return args[0].apply(var) * args[1].apply(var);
+		case PDiv : 
+			{
+				double arg1 = args[1].apply(var);
+				if (arg1 == 0.0)
+					return 1.0; // protection a la Koza, realistic implementations should maybe throw an exception
+
+				return args[0].apply(var) / arg1;
+			}
+
+		case X    : return var; 
+		}
+
+        return var; // to avoid compiler error
+	}
+
+    /// 'Pretty' print to ostream function
+    template <class Children>
+        string operator()(string dummy, Children args)
+    {
+        static const string lb = "(";
+        static const string rb = ")";
+        char opStr[4] = "   ";
+        opStr[1] = op;
+        
+	    if (arity() == 0)
+		{
+            return string("x");
+        }
+        // else
+        string result = lb + args[0].apply(dummy);
+        result += opStr; 
+        result += args[1].apply(dummy) + rb;
+        return result;
+    }
+
+    Operator getOp(void) const { return op; }    
+
+protected :
+
+	void init(void)					{ op = X; }
+
+private :
+
+	Operator op; // the type of node
+};
+
+/// initializor
+static SymregNode init_sequence[5] = {SymregNode::X, SymregNode::Plus, SymregNode::Min, SymregNode::Mult, SymregNode::PDiv}; // needed for intialization
+
+//-----------------------------------------------------------
+// saving, loading
+
+std::ostream& operator<<(std::ostream& os, const SymregNode& eot)
+{
+    os << static_cast<char>(eot.getOp());
+    return os;
+}
+
+std::istream& operator>>(std::istream& is, SymregNode& eot)
+{
+    char type;
+    type = (char) is.get();
+    eot = SymregNode(static_cast<SymregNode::Operator>(type));
+    return is;
+}
+
+
+//-----------------------------------------------------------------------------
+/** Implementation of a function evaluation object. */
+
+float targetFunction(float x)
+{ 
+	return x * x * x * x - x * x * x + x * x * x - x * x + x - 1; 
+}
+
+// parameters controlling the sampling of points
+const float xbegin = -10.0f;
+const float xend   = 10.0f;
+const float xstep  = 1.3f; 
+
+template <class FType, class Node> struct RMS: public eoEvalFunc< eoParseTree<FType, Node> > 
+{
+public :
+
+    typedef eoParseTree<FType, Node> EoType;
+
+    typedef eoParseTree<FType, Node> argument_type;
+    typedef double                   fitness_type;
+
+	RMS(void) : eoEvalFunc<EoType>()
+	{
+		int n = int( (xend - xbegin) / xstep);
+		
+		inputs.resize(n);
+		target.resize(n);
+
+		int i = 0;
+
+    	for (double x = xbegin; x < xend && i < n; ++i)
+		{
+			target[i] = targetFunction(x);
+			inputs[i] = x;
+		}
+	}
+
+    ~RMS() {}
+    
+	void operator()( EoType & _eo ) const 
+	{
+		vector<double> outputs;
+		outputs.resize(inputs.size());
+		
+        double fitness = 0.0;
+        
+		for (int i = 0; i < inputs.size(); ++i)
+        {
+		    outputs[i] = _eo.apply(inputs[i]);
+	        fitness += (outputs[i] - target[i]) * (outputs[i] - target[i]);
+        }
+		
+        fitness /= (double) target.size();
+        fitness = sqrt(fitness);
+			
+		if (fitness > 1e+20)
+			fitness = 1e+20;
+
+		_eo.fitness(fitness);
+	}
+
+private :
+	vector<double> inputs;
+	vector<double> target;
+};
+
+#include "eoTerm.h"
+
+template <class EOT>
+class eoGenerationTerm : public eoTerm<EOT>
+{
+    public :
+        eoGenerationTerm(size_t _ngen) : eoTerm<EOT>(), ngen(_ngen) {}
+
+        bool operator()(const eoPop<EOT>&)
+        {
+            cout << '.'; // pacifier
+            cout.flush();
+
+            return --ngen > 0;
+        }
+    private :
+        unsigned ngen;
+};
+
+template <class EOT, class FitnessType>
+void print_best(eoPop<EOT>& pop)
+{
+    cout << endl;
+    FitnessType best = pop[0].fitness();
+    int index = 0;
+
+    for (int i = 1; i < pop.size(); ++i)
+    {
+        if (best < pop[i].fitness())
+        {
+            best = pop[i].fitness();
+            index = i;
+        }
+    }
+    
+    cout << "\t";
+        
+    string str = pop[index].apply(string());
+    
+    cout << str.c_str();
+    cout << endl << "Error = " << pop[index].fitness() << endl;
+}
+
+
+#include <eo>
+#include "eoGOpBreeder.h"
+#include "eoSequentialGOpSelector.h"
+#include "eoProportionalGOpSelector.h"
+#include "eoDetTournamentIndiSelector.h"
+#include "eoDetTournamentInserter.h"
+#include "eoSteadyStateEA.h"
+#include "eoScalarFitness.h"
+
+void main()
+{
+    typedef eoScalarFitness<double, greater<double> > FitnessType;
+    typedef SymregNode GpNode;
+
+    typedef eoParseTree<FitnessType, GpNode> EoType;
+    typedef eoPop<EoType> Pop;	
+
+    const int MaxSize = 75;
+    const int nGenerations = 50;
+
+    // Initializor sequence, contains the allowable nodes
+    vector<GpNode> init(init_sequence, init_sequence + 5);
+
+    // Depth Initializor, defaults to grow method.
+    eoGpDepthInitializer<FitnessType, GpNode> initializer(10, init);
+    
+    // Root Mean Squared Error Measure
+    RMS<FitnessType, GpNode>              eval;
+
+    Pop pop(500, MaxSize, initializer, eval);
+
+    eoSubtreeXOver<FitnessType, GpNode>   xover(MaxSize);
+    eoBranchMutation<FitnessType, GpNode> mutation(initializer, MaxSize);
+
+    eoSequentialGOpSel<EoType>   seqSel;
+
+    seqSel.addOp(mutation, 0.25);
+    seqSel.addOp(xover, 0.75);
+  
+    eoDetTournamentIndiSelector<EoType> selector(5);
+  
+    eoDetTournamentInserter<EoType> inserter(eval, 5);
+  
+    // Terminators
+    eoGenerationTerm<EoType> term(nGenerations);
+
+    // GP generation
+    eoSteadyStateEA<EoType> gp(seqSel, selector, inserter, term);
+
+    cout << "Initialization done" << endl;
+
+    print_best<EoType, FitnessType>(pop);
+
+    try
+    {
+      gp(pop);
+    }
+    catch (exception& e)
+    {
+	    cout << "exception: " << e.what() << endl;;
+	    exit(EXIT_FAILURE);
+    }
+
+    print_best<EoType, FitnessType>(pop);
+}
+