Package samples.integer

Source Code of samples.integer.CostasArrays

/**
*  Copyright (c) 1999-2014, Ecole des Mines de Nantes
*  All rights reserved.
*  Redistribution and use in source and binary forms, with or without
*  modification, are permitted provided that the following conditions are met:
*
*      * Redistributions of source code must retain the above copyright
*        notice, this list of conditions and the following disclaimer.
*      * 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.
*      * Neither the name of the Ecole des Mines de Nantes nor the
*        names of its contributors may be used to endorse or promote products
*        derived from this software without specific prior written permission.
*
*  THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS AND 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 samples.integer;

import org.kohsuke.args4j.Option;
import samples.AbstractProblem;
import solver.Solver;
import solver.constraints.ICF;
import solver.constraints.IntConstraintFactory;
import solver.search.loop.monitors.SMF;
import solver.search.strategy.ISF;
import solver.variables.IntVar;
import solver.variables.VariableFactory;
import util.tools.StringUtils;

/**
* Costas Arrays
* "Given n in N, find an array s = [s_1, ..., s_n], such that
* <ul>
* <li>s is a permutation of Z_n = {0,1,...,n-1};</li>
* <li>the vectors v(i,j) = (j-i)x + (s_j-s_i)y are all different </li>
* </ul>
* <br/>
* An array v satisfying these conditions is called a Costas array of size n;
* the problem of finding such an array is the Costas Array problem of size n."
* <br/>
*
* @author Jean-Guillaume Fages
* @since 25/01/11
*/
public class CostasArrays extends AbstractProblem {

    @Option(name = "-o", usage = "Costas array size.", required = false)
    private static int n = 14// should be <15 to be solved quickly

    IntVar[] vars, vectors;

    @Override
    public void createSolver() {
        solver = new Solver("CostasArrays");
    }

  @Override
  public void buildModel() {
    vars = VariableFactory.enumeratedArray("v", n, 0, n - 1, solver);
    vectors = new IntVar[(n*(n-1))/2];
    IntVar[][] diff = new IntVar[n][n];
    int idx = 0;
    for (int i = 0; i < n; i++) {
      for (int j = i+1; j < n; j++) {
        IntVar k = VariableFactory.enumerated(StringUtils.randomName(), -n, n, solver);
        solver.post(ICF.arithm(k,"!=",0));
        solver.post(IntConstraintFactory.sum(new IntVar[]{vars[i],k},vars[j]));
        vectors[idx] = VariableFactory.offset(k, 2 * n * (j - i));
        diff[i][j] = k;
        idx++;
      }
    }
    solver.post(IntConstraintFactory.alldifferent(vars, "AC"));
    solver.post(IntConstraintFactory.alldifferent(vectors, "BC"));

    // symmetry-breaking
    solver.post(ICF.arithm(vars[0],"<",vars[n-1]));
  }

  @Override
  public void configureSearch() {
    SMF.limitTime(solver,20000);
    solver.set(ISF.lexico_LB(vectors));
  }

    @Override
    public void solve() {
        solver.findSolution();
    }

    @Override
    public void prettyOut() {
        String s = "";
        for (int i = 0; i < n; i++) {
            s += "|";
            for (int j = 0; j < n; j++) {
                if (j == vars[i].getValue()) {
                    s += "x|";
                } else {
                    s += "-|";
                }
            }
            s += "\n";
        }
        System.out.println(s);
    }

    public static void main(String[] args) {
        new CostasArrays().execute(args);
    }
}
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