NodeSelector.h

/*          
 *             Copyright (C) 2005 Maarten Keijzer
 *
 *          This program is free software; you can redistribute it and/or modify
 *          it under the terms of version 2 of the GNU General Public License as 
 *          published by the Free Software Foundation. 
 *
 *          This program is distributed in the hope that it will be useful,
 *          but WITHOUT ANY WARRANTY; without even the implied warranty of
 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *          GNU General Public License for more details.
 *
 *          You should have received a copy of the GNU General Public License
 *          along with this program; if not, write to the Free Software
 *          Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef NODESELECTOR_H
#define NODESELECTOR_H

#include <Sym.h>

class NodeSelector {
    public:
        
    class NodeSelection {
        Sym root_;
        unsigned subtree_index_;
        Sym subtree_;

        public :
            NodeSelection(Sym r, unsigned idx, Sym s) 
                : root_(r), subtree_index_(idx), subtree_(s) {}

            Sym root() const { return root_; }
            unsigned idx()  const { return subtree_index_; }
            Sym subtree(); 
        
    };

    virtual ~NodeSelector() {}
        
    virtual NodeSelection select_node(Sym sym) const = 0;  
};


class RandomNodeSelector : public NodeSelector {
    public:
    NodeSelection select_node(Sym sym) const;
};

class BiasedNodeSelector : public NodeSelector {
    public:
    unsigned nRounds;

    BiasedNodeSelector() : nRounds(3) {} // 3: for binary trees 87.5% chance of selecting an internal node
    BiasedNodeSelector(unsigned n) : nRounds(n) {}
    
    NodeSelection select_node(Sym sym) const;
};

#endif

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