content: /**
   * Copyright (c) 2017 Siemens AG
   * All rights reserved.
   * 
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   * 
   * 1) Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   * 
   * 2) Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   * 
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  package at.ac.tuwien.kr.alpha.core.solver.heuristics;
  
  import at.ac.tuwien.kr.alpha.core.common.Assignment;
  import at.ac.tuwien.kr.alpha.core.solver.ChoiceManager;
  import at.ac.tuwien.kr.alpha.core.solver.ThriceTruth;
  import at.ac.tuwien.kr.alpha.core.solver.heuristics.activity.BodyActivityProviderFactory.BodyActivityType;
  
  import static at.ac.tuwien.kr.alpha.core.solver.Atoms.isAtom;
  
  import java.util.Random;
  
  public class AlphaRandomSignHeuristic extends DependencyDrivenHeuristic {
  
  	public AlphaRandomSignHeuristic(Assignment assignment, ChoiceManager choiceManager, int decayPeriod, double decayFactor, Random random) {
  		super(assignment, choiceManager, decayPeriod, decayFactor, random, BodyActivityType.DEFAULT);
  	}
  
  	public AlphaRandomSignHeuristic(Assignment assignment, ChoiceManager choiceManager, Random random) {
  		super(assignment, choiceManager, random);
  	}
  
  	@Override
  	protected void incrementSignCounter(Integer literal) {
  		LOGGER.trace("AlphaRandomSignHeuristic does NOT increment sign counters because they are not needed.");
  	}
  
  	@Override
  	public boolean chooseSign(int atom) {
  		if (!isAtom(atom)) {
  			throw new IllegalArgumentException("Atom must be a positive integer.");
  		}
  
  		if (assignment.getTruth(atom) == ThriceTruth.MBT) {
  			return true;
  		}
  
  		return rand.nextBoolean();
  	}
  
  }
  