UCTPlusSelector.java

/**
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 *  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.
 */
package bots.mctsbot.ai.bots.bot.gametree.mcts.strategies.selection;

import bots.mctsbot.ai.bots.bot.gametree.mcts.nodes.INode;

public class UCTPlusSelector extends MaxFunctionSelector {

	private final double C1;
	private final double C2;

	public UCTPlusSelector(double C1, double C2) {
		this.C1 = C1;
		this.C2 = C2;
	}

	@Override
	protected double evaluate(INode node) {
		int nbSamples = node.getNbSamples();
		if (nbSamples == 0)
			return 0;
		int nbParentSamples = node.getParent().getNbSamples();
		double stdDev = node.getEVStdDev();
		return node.getEV() + C1 * Math.sqrt(Math.log(nbParentSamples) / nbSamples) + C2 * stdDev;
	}

}