/*******************************************************************************
* SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU Lesser General Public License Version 2.1 or later (the
* "LGPL"), in which case the provisions of the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of the LGPL, and not to allow others to use your version of
* this file under the terms of the EPL, indicate your decision by deleting
* the provisions above and replace them with the notice and other provisions
* required by the LGPL. If you do not delete the provisions above, a recipient
* may use your version of this file under the terms of the EPL or the LGPL.
*
* Based on the original MiniSat specification from:
*
* An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
* Sixth International Conference on Theory and Applications of Satisfiability
* Testing, LNCS 2919, pp 502-518, 2003.
*
* See www.minisat.se for the original solver in C++.
*
*******************************************************************************/
package org.sat4j.reader;
import java.io.IOException;
import java.io.LineNumberReader;
import java.io.PrintWriter;
import java.io.Serializable;
import java.util.Scanner;
import java.util.StringTokenizer;
import org.sat4j.core.VecInt;
import org.sat4j.specs.ContradictionException;
import org.sat4j.specs.IProblem;
import org.sat4j.specs.ISolver;
import org.sat4j.specs.IVecInt;
/**
* Very simple Dimacs file parser. Allow solvers to read the constraints from a
* Dimacs formatted file. It should be used that way:
*
* <pre>
* DimacsReader solver = new DimacsReader(SolverFactory.OneSolver());
* solver.readInstance("mybench.cnf");
* if (solver.isSatisfiable()) {
* // SAT case
* } else {
* // UNSAT case
* }
* </pre>
*
* That parser is not used for efficiency reasons. It will be updated with Java
* 1.5 scanner feature.
*
* @version 1.0
* @author dlb
* @author or
*/
public class DimacsReader extends Reader implements Serializable {
private static final long serialVersionUID = 1L;
protected int expectedNbOfConstr; // as announced on the p cnf line
protected final ISolver solver;
private boolean checkConstrNb = true;
protected final String formatString;
public DimacsReader(ISolver solver) {
this(solver, "cnf");
}
public DimacsReader(ISolver solver, String format) {
this.solver = solver;
formatString = format;
}
public void disableNumberOfConstraintCheck() {
checkConstrNb = false;
}
/**
* Skip comments at the beginning of the input stream.
*
* @param in
* the input stream
* @throws IOException
* if an IO problem occurs.
*/
protected void skipComments(final LineNumberReader in) throws IOException {
int c;
do {
in.mark(4);
c = in.read();
if (c == 'c') {
in.readLine();
} else {
in.reset();
}
} while (c == 'c');
}
/**
* @param in
* the input stream
* @throws IOException
* iff an IO occurs
* @throws ParseFormatException
* if the input stream does not comply with the DIMACS format.
*/
protected void readProblemLine(LineNumberReader in) throws IOException,
ParseFormatException {
String line = in.readLine();
if (line == null) {
throw new ParseFormatException(
"premature end of file: <p cnf ...> expected on line "
+ in.getLineNumber());
}
StringTokenizer stk = new StringTokenizer(line);
if (!(stk.hasMoreTokens() && stk.nextToken().equals("p")
&& stk.hasMoreTokens() && stk.nextToken().equals(formatString))) {
throw new ParseFormatException(
"problem line expected (p cnf ...) on line "
+ in.getLineNumber());
}
int vars;
// reads the max var id
vars = Integer.parseInt(stk.nextToken());
assert vars > 0;
solver.newVar(vars);
// reads the number of clauses
expectedNbOfConstr = Integer.parseInt(stk.nextToken());
assert expectedNbOfConstr > 0;
solver.setExpectedNumberOfClauses(expectedNbOfConstr);
}
/**
* @param in
* the input stream
* @throws IOException
* iff an IO problems occurs
* @throws ParseFormatException
* if the input stream does not comply with the DIMACS format.
* @throws ContradictionException
* si le probl?me est trivialement inconsistant.
*/
protected void readConstrs(LineNumberReader in) throws IOException,
ParseFormatException, ContradictionException {
String line;
int realNbOfConstr = 0;
IVecInt literals = new VecInt();
while (true) {
line = in.readLine();
if (line == null) {
// end of file
if (literals.size() > 0) {
// no 0 end the last clause
solver.addClause(literals);
realNbOfConstr++;
}
break;
}
if (line.startsWith("c ")) {
// ignore comment line
continue;
}
if (line.startsWith("%") && expectedNbOfConstr == realNbOfConstr) {
System.out
.println("Ignoring the rest of the file (SATLIB format");
break;
}
boolean added = handleConstr(line, literals);
if (added) {
realNbOfConstr++;
}
}
if (checkConstrNb && expectedNbOfConstr != realNbOfConstr) {
throw new ParseFormatException("wrong nbclauses parameter. Found "
+ realNbOfConstr + ", " + expectedNbOfConstr + " expected");
}
}
protected boolean handleConstr(String line, IVecInt literals)
throws ContradictionException {
int lit;
boolean added = false;
Scanner scan;
scan = new Scanner(line);
while (scan.hasNext()) {
lit = scan.nextInt();
if (lit == 0) {
if (literals.size() > 0) {
solver.addClause(literals);
literals.clear();
added = true;
}
} else {
literals.push(lit);
}
}
return added;
}
@Override
public final IProblem parseInstance(final java.io.Reader in)
throws ParseFormatException, ContradictionException, IOException {
return parseInstance(new LineNumberReader(in));
}
/**
* @param in
* the input stream
* @throws ParseFormatException
* if the input stream does not comply with the DIMACS format.
* @throws ContradictionException
* si le probl?me est trivialement inconsitant
*/
private IProblem parseInstance(LineNumberReader in)
throws ParseFormatException, ContradictionException {
solver.reset();
try {
skipComments(in);
readProblemLine(in);
readConstrs(in);
return solver;
} catch (IOException e) {
throw new ParseFormatException(e);
} catch (NumberFormatException e) {
throw new ParseFormatException("integer value expected on line "
+ in.getLineNumber(), e);
}
}
@Override
public String decode(int[] model) {
StringBuffer stb = new StringBuffer();
for (int i = 0; i < model.length; i++) {
stb.append(model[i]);
stb.append(" ");
}
stb.append("0");
return stb.toString();
}
@Override
public void decode(int[] model, PrintWriter out) {
for (int i = 0; i < model.length; i++) {
out.print(model[i]);
out.print(" ");
}
out.print("0");
}
protected ISolver getSolver() {
return solver;
}
}