content: /**
   * Copyright (c) 2018-2019 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 static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  import java.util.Arrays;
  import java.util.Collection;
  
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  
  import at.ac.tuwien.kr.alpha.core.common.AtomStore;
  import at.ac.tuwien.kr.alpha.core.common.AtomStoreImpl;
  import at.ac.tuwien.kr.alpha.core.common.NoGood;
  import at.ac.tuwien.kr.alpha.core.programs.atoms.Literals;
  import at.ac.tuwien.kr.alpha.core.solver.NoGoodStoreAlphaRoaming;
  import at.ac.tuwien.kr.alpha.core.solver.TrailAssignment;
  import at.ac.tuwien.kr.alpha.core.solver.WritableAssignment;
  import at.ac.tuwien.kr.alpha.core.solver.learning.GroundConflictNoGoodLearner.ConflictAnalysisResult;
  import at.ac.tuwien.kr.alpha.core.test.util.TestUtils;
  
  /**
   * Tests {@link VSIDS}.
   *
   */
  public class VSIDSTest {
  
  	/**
  	 * The tolerable epsilon for double comparisons
  	 */
  	private static final double DOUBLE_COMPARISON_EPSILON = 0.000001;
  
  	private VSIDS vsids;
  	private AtomStore atomStore;
  	private WritableAssignment assignment;
  	private NoGoodStoreAlphaRoaming noGoodStore;
  
  	private int lit1Neg = Literals.atomToLiteral(1, false);
  	private int lit2Neg = Literals.atomToLiteral(2, false);
  	private int lit3Neg = Literals.atomToLiteral(3, false);
  	private int lit4Neg = Literals.atomToLiteral(4, false);
  	private int lit1 = Literals.atomToLiteral(1);
  	private int lit2 = Literals.atomToLiteral(2);
  	private int lit3 = Literals.atomToLiteral(3);
  	private int lit4 = Literals.atomToLiteral(4);
  
  	@BeforeEach
  	public void setUp() {
  		atomStore = new AtomStoreImpl();
  		TestUtils.fillAtomStore(atomStore, 4);
  		assignment = new TrailAssignment(atomStore);
  		assignment.growForMaxAtomId();
  		noGoodStore = new NoGoodStoreAlphaRoaming(assignment);
  		this.vsids = new VSIDS(
  				assignment,
  				new PseudoChoiceManager(assignment, noGoodStore),
  				null);
  	}
  
  	/**
  	 * Tests the following artificial situation:
  	 * Static nogoods: { {-1, -2}, {-3, -4}}
  	 * Learnt nogood: { 2, 3 }
  	 * Atoms resolved out during conflict analysis: { 1 }
  	 */
  	@Test
  	public void testConflict() {
  		HeuristicTestUtils.addNoGoods(atomStore, assignment, noGoodStore, vsids, new NoGood(lit1Neg, lit2Neg), new NoGood(lit3Neg, lit4Neg));
  		vsids.chooseLiteral(); // to make VSIDS ingest buffered nogoods
  		assertEquals(vsids.getActivity(lit1), vsids.getActivity(lit2), DOUBLE_COMPARISON_EPSILON);
  		assertEquals(vsids.getActivity(lit2), vsids.getActivity(lit3), DOUBLE_COMPARISON_EPSILON);
  		assertEquals(vsids.getActivity(lit3), vsids.getActivity(lit4), DOUBLE_COMPARISON_EPSILON);
  
  		NoGood learnedNoGood = new NoGood(lit2, lit3);
  		Collection<Integer> resolutionAtoms = Arrays.asList(1);
  		ConflictAnalysisResult analysisResult = new ConflictAnalysisResult(learnedNoGood, 1, resolutionAtoms);
  		vsids.analyzedConflict(analysisResult);
  		assertEquals(vsids.getActivity(lit1), vsids.getActivity(lit2), DOUBLE_COMPARISON_EPSILON);
  		assertEquals(vsids.getActivity(lit2), vsids.getActivity(lit3), DOUBLE_COMPARISON_EPSILON);
  		assertLessThan(vsids.getActivity(lit4), vsids.getActivity(lit3));
  
  		assertEquals(0, vsids.getSignBalance(1));
  		assertEquals(1, vsids.getSignBalance(2));
  		assertEquals(1, vsids.getSignBalance(3));
  		assertEquals(0, vsids.getSignBalance(4));
  	}
  
  	/**
  	 * First, calls {@link #testConflict()}.
  	 * Then, simulates a second conflict, learning { -1, 4 } with resolved atoms { 2 }.
  	 * Due to decay, scores of atoms { 1, 4, 2 } must increase by the increased activity delta of {@link VSIDS#DEFAULT_DECAY_FACTOR}.
  	 * 
  	 */
  	@Test
  	public void testTwoConflicts() {
  		testConflict();
  
  		double activity1 = vsids.getActivity(lit1);
  		double activity2 = vsids.getActivity(lit2);
  		double activity3 = vsids.getActivity(lit3);
  		double activity4 = vsids.getActivity(lit4);
  
  		NoGood learnedNoGood = new NoGood(lit1Neg, lit4);
  		Collection<Integer> resolutionAtoms = Arrays.asList(2);
  		ConflictAnalysisResult analysisResult = new ConflictAnalysisResult(learnedNoGood, 1, resolutionAtoms);
  		vsids.analyzedConflict(analysisResult);
  		assertEquals(activity1 + VSIDS.DEFAULT_DECAY_FACTOR, vsids.getActivity(lit1), DOUBLE_COMPARISON_EPSILON);
  		assertEquals(activity2 + VSIDS.DEFAULT_DECAY_FACTOR, vsids.getActivity(lit2), DOUBLE_COMPARISON_EPSILON);
  		assertEquals(activity3, vsids.getActivity(lit3), DOUBLE_COMPARISON_EPSILON);
  		assertEquals(activity4 + VSIDS.DEFAULT_DECAY_FACTOR, vsids.getActivity(lit4), DOUBLE_COMPARISON_EPSILON);
  
  		assertEquals(-1, vsids.getSignBalance(1));
  		assertEquals(1, vsids.getSignBalance(2));
  		assertEquals(1, vsids.getSignBalance(3));
  		assertEquals(1, vsids.getSignBalance(4));
  	}
  
  	private static void assertLessThan(double d1, double d2) {
  		assertTrue(d1 < d2 + DOUBLE_COMPARISON_EPSILON);
  	}
  }
  