/*
* Kodkod -- Copyright (c) 2005-present, Emina Torlak
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package kodkod.examples.csp;
import kodkod.ast.Formula;
import kodkod.ast.Relation;
import kodkod.engine.Evaluator;
import kodkod.engine.Solution;
import kodkod.engine.Solver;
import kodkod.engine.config.ConsoleReporter;
import kodkod.engine.satlab.SATFactory;
import kodkod.instance.Bounds;
import kodkod.instance.Instance;
import kodkod.instance.TupleFactory;
import kodkod.instance.TupleSet;
import kodkod.instance.Universe;
/**
* Reads a graph from a file, formatted using the DIMACS or the ASP (http://asparagus.cs.uni-potsdam.de/?action=instances&id=30) graph format,
* and finds a Hamiltonian cycle in it if one exists.
*
* @author Emina Torlak
*/
public final class HamiltonianCycle {
private final Relation vertex, start, edges, cycle;
/**
* Constructs an instance of the encoding.
*/
public HamiltonianCycle() {
this.vertex = Relation.unary("Vertex");
this.start = Relation.unary("start");
this.edges = Relation.binary("edges");
this.cycle = Relation.binary("cycle");
}
/**
* Returns a formula that defines a Hamiltonian cycle.
* @return a formula that defines a Hamiltonian cycle
*/
public Formula cycleDefinition() {
final Formula f0 = cycle.function(edges.join(vertex), vertex.join(edges));
final Formula f1 = vertex.in(start.join(cycle.closure()));
return f0.and(f1);
}
/**
* Returns Bounds extracted from the graph
* definition in the given file.
* @requires file is in the specified format
* @return Bounds extracted from the graph
* definition in the given file.
*/
public Bounds bounds(String file, Graph.Format format) {
final Graph<?> graph = format.parse(file);
final Universe u = new Universe(graph.nodes());
final TupleFactory f = u.factory();
final Bounds b = new Bounds(u);
b.boundExactly(vertex, f.allOf(1));
b.boundExactly(start, f.setOf(graph.start()==null ? u.atom(0) : graph.start()));
final TupleSet edgeBound = f.noneOf(2);
for(Object from : graph.nodes()) {
for (Object to : graph.edges(from))
edgeBound.add(f.tuple(from, to));
}
b.boundExactly(edges, edgeBound);
b.bound(cycle, edgeBound);
return b;
}
private static void usage() {
System.out.println("Usage: examples.classicnp.HamiltonianCycle <graph file> <file format>");
System.exit(1);
}
private final boolean verify(Instance instance) {
final Evaluator eval = new Evaluator(instance);
System.out.println(eval.evaluate(cycle));
return eval.evaluate(cycleDefinition());
}
/**
* Usage: examples.classicnp.HamiltonianCycle <graph file> <DIMACS | ASP>
*/
public static void main(String[] args) {
if (args.length!=2)
usage();
final HamiltonianCycle model = new HamiltonianCycle();
final Formula f = model.cycleDefinition();
final Bounds b = model.bounds(args[0], Enum.valueOf(Graph.Format.class, args[1].toUpperCase()));
System.out.println(f);
System.out.println(b);
final Solver solver = new Solver();
solver.options().setSolver(SATFactory.MiniSat);
solver.options().setReporter(new ConsoleReporter());
// solver.options().setFlatten(false);
final Solution s = solver.solve(f,b);
System.out.println(s);
if (s.instance()!=null) {
System.out.print("verifying solution ... ");
System.out.println(model.verify(s.instance()) ? "correct." : "incorrect!");
}
}
}
