jp.ac.kobe_u.cs.cream.NeighborhoodSearchSolver Maven / Gradle / Ivy

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package jp.ac.kobe_u.cs.cream;

/**
 * A branch-and-bound solver with preset values. An array of initial values can be passed as an
 * argument to the solver.
 *
 * 
 *   The solver tries to preset the initial values to the variables as mush as possible until it
 *       violates some constraint.
 *   
Remaining variable values are determined by a backtrack search.
 *   
Preset values are also undone when the problem is unsatisfiable during the further search.
 *   
The changes are not ensured to the minimum changes.
 * 
 *
 * @see Solver
 * @see DefaultSolver
 * @author Naoyuki Tamura ([email protected])
 */
public class NeighborhoodSearchSolver extends DefaultSolver {
  private int[] values;

  public NeighborhoodSearchSolver(Network network, int[] values) {
    this(network, values, DEFAULT, null);
  }

  public NeighborhoodSearchSolver(Network network, int[] values, int options) {
    this(network, values, options, null);
  }

  public NeighborhoodSearchSolver(Network network, int[] values, String name) {
    this(network, values, DEFAULT, name);
  }

  public NeighborhoodSearchSolver(Network network, int[] values, int options, String name) {
    super(network, options, name);
    this.values = values;
  }

  @Override
  public void run() {
    clearBest();
    Trail trail = getTrail();
    if (values != null) {
      // Preset values[i] to the i-th variable as much as possible
      for (int i = 0; i < values.length; i++) {
        Variable v = network.getVariable(i);
        int t0 = trail.size();
        // Preset values[i] to the i-th variable
        v.updateDomain(new IntDomain(values[i]), trail);
        if (!satisfy()) {
          // Preset value violates some constraint
          trail.undo(t0);
          break;
        }
      }
    }
    // Invoke DefaultSolver
    solve(0);
    trail.undo(0);
    fail();
  }
}