001 /*
002 * Created on Dec 4, 2004
003 *
004 */
005 package aima.test.logictest.prop.algorithms;
006
007 import java.util.List;
008
009 import junit.framework.TestCase;
010 import aima.logic.propositional.algorithms.DPLL;
011 import aima.logic.propositional.algorithms.KnowledgeBase;
012 import aima.logic.propositional.algorithms.Model;
013 import aima.logic.propositional.parsing.PEParser;
014 import aima.logic.propositional.parsing.ast.Sentence;
015 import aima.logic.propositional.parsing.ast.Symbol;
016 import aima.logic.propositional.visitors.CNFClauseGatherer;
017 import aima.logic.propositional.visitors.CNFTransformer;
018 import aima.logic.propositional.visitors.SymbolCollector;
019 import aima.util.Converter;
020
021 /**
022 * @author Ravi Mohan
023 *
024 */
025
026 public class DPLLTest extends TestCase {
027
028 private KnowledgeBase one, two, three, four;
029
030 private DPLL dpll;
031
032 private PEParser parser;
033
034 @Override
035 public void setUp() {
036 parser = new PEParser();
037 dpll = new DPLL();
038 }
039
040 public void testDPLLReturnsTrueWhenAllClausesTrueInModel() {
041 Model model = new Model();
042 model = model.extend(new Symbol("A"), true).extend(new Symbol("B"),
043 true);
044 Sentence sentence = (Sentence) parser.parse("((A AND B) AND (A OR B))");
045 boolean satisfiable = dpll.dpllSatisfiable(sentence, model);
046 assertEquals(true, satisfiable);
047 }
048
049 public void testDPLLReturnsFalseWhenOneClauseFalseInModel() {
050 Model model = new Model();
051 model = model.extend(new Symbol("A"), true).extend(new Symbol("B"),
052 false);
053 Sentence sentence = (Sentence) parser.parse("((A OR B) AND (A => B))");
054 boolean satisfiable = dpll.dpllSatisfiable(sentence, model);
055 assertEquals(false, satisfiable);
056 }
057
058 public void testDPLLFiltersClausesTheStatusOfWhichAreKnown() {
059 Model model = new Model();
060 model = model.extend(new Symbol("A"), true).extend(new Symbol("B"),
061 true);
062 Sentence sentence = (Sentence) parser
063 .parse("((A AND B) AND (B AND C))");
064 List<Sentence> clauseList = new Converter<Sentence>()
065 .setToList(new CNFClauseGatherer()
066 .getClausesFrom(new CNFTransformer()
067 .transform(sentence)));
068 List clausesWithNonTrueValues = dpll.clausesWithNonTrueValues(
069 clauseList, model);
070 assertEquals(1, clausesWithNonTrueValues.size());
071 Sentence nonTrueClause = (Sentence) parser.parse("(B AND C)");
072 clausesWithNonTrueValues.contains(nonTrueClause);
073 }
074
075 public void testDPLLFilteringNonTrueClausesGivesNullWhenAllClausesAreKnown() {
076 Model model = new Model();
077 model = model.extend(new Symbol("A"), true).extend(new Symbol("B"),
078 true).extend(new Symbol("C"), true);
079 Sentence sentence = (Sentence) parser
080 .parse("((A AND B) AND (B AND C))");
081 List<Sentence> clauseList = new Converter<Sentence>()
082 .setToList(new CNFClauseGatherer()
083 .getClausesFrom(new CNFTransformer()
084 .transform(sentence)));
085 List clausesWithNonTrueValues = dpll.clausesWithNonTrueValues(
086 clauseList, model);
087 assertEquals(0, clausesWithNonTrueValues.size());
088 }
089
090 public void testDPLLFindsPurePositiveSymbolsWhenTheyExist() {
091 Model model = new Model();
092 model = model.extend(new Symbol("A"), true).extend(new Symbol("B"),
093 true);
094 Sentence sentence = (Sentence) parser
095 .parse("((A AND B) AND (B AND C))");
096 List<Sentence> clauseList = new Converter<Sentence>()
097 .setToList(new CNFClauseGatherer()
098 .getClausesFrom(new CNFTransformer()
099 .transform(sentence)));
100 List<Symbol> symbolList = new Converter<Symbol>()
101 .setToList(new SymbolCollector().getSymbolsIn(sentence));
102
103 DPLL.SymbolValuePair sv = dpll.findPureSymbolValuePair(clauseList,
104 model, symbolList);
105 assertNotNull(sv);
106 assertEquals(new Symbol("C"), sv.symbol);
107 assertEquals(new Boolean(true), sv.value);
108 }
109
110 public void testDPLLFindsPureNegativeSymbolsWhenTheyExist() {
111 Model model = new Model();
112 model = model.extend(new Symbol("A"), true).extend(new Symbol("B"),
113 true);
114 Sentence sentence = (Sentence) parser
115 .parse("((A AND B) AND ( B AND (NOT C) ))");
116 List<Sentence> clauseList = new Converter<Sentence>()
117 .setToList(new CNFClauseGatherer()
118 .getClausesFrom(new CNFTransformer()
119 .transform(sentence)));
120 List<Symbol> symbolList = new Converter<Symbol>()
121 .setToList(new SymbolCollector().getSymbolsIn(sentence));
122
123 DPLL.SymbolValuePair sv = dpll.findPureSymbolValuePair(clauseList,
124 model, symbolList);
125 assertNotNull(sv);
126 assertEquals(new Symbol("C"), sv.symbol);
127 assertEquals(new Boolean(false), sv.value);
128 }
129
130 public void testDPLLSucceedsWithAandNotA() {
131 Sentence sentence = (Sentence) parser.parse("(A AND (NOT A))");
132 boolean satisfiable = dpll.dpllSatisfiable(sentence);
133 assertEquals(false, satisfiable);
134 }
135
136 public void testDPLLSucceedsWithChadCarffsBugReport() {
137 KnowledgeBase kb = new KnowledgeBase();
138 kb.tell("(B12 <=> (P11 OR (P13 OR (P22 OR P02))))");
139 kb.tell("(B21 <=> (P20 OR (P22 OR (P31 OR P11))))");
140 kb.tell("(B01 <=> (P00 OR (P02 OR P11)))");
141 kb.tell("(B10 <=> (P11 OR (P20 OR P00)))");
142 kb.tell("(NOT B21)");
143 kb.tell("(NOT B12)");
144 kb.tell("(B10)");
145 kb.tell("(B01)");
146 assertTrue(kb.askWithDpll("(P00)"));
147 assertFalse(kb.askWithDpll("(NOT P00)"));
148
149 }
150
151 public void testDPLLSucceedsWithStackOverflowBugReport1() {
152 KnowledgeBase kb = new KnowledgeBase();
153 Sentence sentence = (Sentence) parser
154 .parse("((A OR (NOT A)) AND (A OR B))");
155 assertTrue(dpll.dpllSatisfiable(sentence));
156
157 }
158
159 public void testDPLLSucceedsWithChadCarffsBugReport2() {
160 KnowledgeBase kb = new KnowledgeBase();
161 kb.tell("(B10 <=> (P11 OR (P20 OR P00)))");
162 kb.tell("(B01 <=> (P00 OR (P02 OR P11)))");
163 kb.tell("(B21 <=> (P20 OR (P22 OR (P31 OR P11))))");
164 kb.tell("(B12 <=> (P11 OR (P13 OR (P22 OR P02))))");
165 kb.tell("(NOT B21)");
166 kb.tell("(NOT B12)");
167 kb.tell("(B10)");
168 kb.tell("(B01)");
169 assertTrue(kb.askWithDpll("(P00)"));
170 assertFalse(kb.askWithDpll("(NOT P00)"));
171
172 }
173
174 }