Re: [Choco-users] Newbie question: constrained and instantiated events.

[Guillaume R. <ro...@gm...>]

Hi,

Well, this is not really an available feature right now. But you can
simulate it easily. For instance, you can do a fake constraint which
only watch events on all variables. For instance you can use the
following code.

Hope it helps,

Guillaume


===============

package mestests;

import choco.integer.IntDomainVar;
import choco.integer.constraints.AbstractLargeIntConstraint;
import choco.ContradictionException;
import choco.Problem;

/**
 * Created by IntelliJ IDEA.
 * User: grochart
 * Date: 5 juin 2007
 * Time: 09:58:16
 * To change this template use File | Settings | File Templates.
 */
public class TestVarListener {

  static class VarListener extends AbstractLargeIntConstraint {
    public VarListener(IntDomainVar[] vars) {
      super(vars);
    }


    public void propagate() throws ContradictionException {
      // Nothing is done !
    }

    public void awakeOnInf(int idx) throws ContradictionException {
      System.out.println("Lower bound of " + getIntVar(idx) + " was
increased !");
    }

    public void awakeOnSup(int idx) throws ContradictionException {
      System.out.println("Upper bound of " + getIntVar(idx) + " was
decreased !");
    }

    public void awakeOnInst(int idx) throws ContradictionException {
      System.out.println(getIntVar(idx) + " was instantiated !");
    }

    public void awakeOnRem(int idx, int x) throws ContradictionException {
      System.out.println("Value " + x + " of " + getIntVar(idx) + "
was removed !");
    }

    public boolean isSatisfied() {
      return true;
    }
  }

  public static final int NB_REINES = 8;


  public static void main(String[] args) {
    long time = System.currentTimeMillis();
    System.out.println("NReine model 2");

    // ******* 0. Problem creation **********
    Problem pb = new Problem();

    // ******* 1. Variables creations *********
    IntDomainVar[] vars =
        createVariables(pb);

    // ******* 2. Constraints posting *********
    postConstraints(pb, vars);

    // ******* 3. Heuristic *********
    setHeuristic(pb);

    // ******* 4. Solving *********
    pb.solve();

    // ******* 5. Displaying solution *********
    displayResult(pb, vars);

    System.out.println("Time ellapsed: " + (System.currentTimeMillis()
- time) + "ms.");
  }

  private static IntDomainVar[] createVariables(Problem pb) {
    IntDomainVar[] vars = new IntDomainVar[NB_REINES];
    for (int i = 0; i < NB_REINES; i++) {
      vars[i] = pb.makeEnumIntVar("x" + i, 0, NB_REINES - 1);
    }
    return vars;
  }

  private static void postConstraints(Problem pb, IntDomainVar[] vars) {
    postConstraints1(pb, vars);
    postConstraints2(pb, vars);
    pb.post(new VarListener(vars));
  }

  private static void postConstraints1(Problem pb, IntDomainVar[] vars) {
    for(int i = 0; i < NB_REINES; i++) {
      for(int j = i+1; j < NB_REINES; j++) {
        pb.post(pb.neq(vars[i], vars[j]));
      }
    }
  }

  private static void postConstraints2(Problem pb, IntDomainVar[] vars) {
    for (int i = 0; i < NB_REINES; i++) {
      for (int j = i + 1; j < NB_REINES; j++) {
        int k = j - i;
        pb.post(pb.neq(vars[i], pb.plus(vars[j], k)));
        pb.post(pb.neq(vars[i], pb.minus(vars[j], k)));
      }
    }
  }

  private static void setHeuristic(Problem pb) {
    //pb.getSolver().setValIterator(new DecreasingDomain());
  }

  private static void displayResult(Problem pb, IntDomainVar[] vars) {
    if (pb.getSolver().getNbSolutions() > 0) {
      System.out.println("Found solution : ");
      for (int i = 0; i < NB_REINES; i++) {
        int val = vars[i].getVal();
        for (int j = 0; j < NB_REINES; j++) {
          System.out.print(val == j ? "R " : ". ");
        }
        System.out.println("");
      }
    } else {
      System.out.println("No solution found !!");
    }
  }
}


===============




On 6/5/07, Malcolm Ryan <mal...@cs...> wrote:
> Hi,
>
> I've been doing some constraint programming in ECLiPSe prolog, but
> the language is beginning to really annoy me and I've been thinking
> about migrating to a different platform. Choco looks like a
> possibility, but I need to make sure it can do the things I need.
> Eclipse has an event model whereby you can set an action to occur
> when a particular event occurs on a variable. Defined events include
> an event whenever the domain is constrained and an event when the
> variable is instantiated. Is there an equivalent functionality in Choco?
>
> Malcolm
>
> --
> Many clever men like you have trusted to civilisation.
> Many clever Babylonians, many clever Egyptians,
> Many clever men at the end of Rome.
>                                - G.K.Chesterton, The Napoleon of
> Notting Hill
>
>
>
>
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