javax.constraints.impl.search.selectors.VarSelectorMinDomain Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of jsr331 Show documentation

JCP Standard JSR331 “Java Constraint Programming API”. It is used for Modeling and Solving Constraint Satisfaction and Optimization Problems using Java and off-the-shelf Constraint/Linear Solvers

The newest version!

//=============================================
// J A V A  C O M M U N I T Y  P R O C E S S
// 
// J S R  3 3 1
// 
// Common Implementation
// 
//=============================================
package javax.constraints.impl.search.selectors;

/**
 * This class creates a selector that selects an unbound constrained
 * variable from a given array of variables by this criteria:
 * "min size of domain, random tie break"
 */

import javax.constraints.SearchStrategy;
import javax.constraints.Var;
import javax.constraints.VarSelectorType;

public class VarSelectorMinDomain extends AbstractVarSelector {
	
	public VarSelectorType getType() {
		return VarSelectorType.INPUT_ORDER;
	}

	/**
	 * Constructor from SearchStrategy strategy
	 */
	public VarSelectorMinDomain(SearchStrategy strategy) {
		super(strategy);
	}

	/**
	 * Returns the index of the selected variable:
	 * "min size of domain, random tie break".
	 * If no variables to select, it returns -1;
	 */
	public int select() {
		int minSize = Integer.MAX_VALUE;
	    int minIndex = -1;
		for(int i=0; i < getVars().length; i++) {
			Var var = getVars()[i];
			if (var.isBound())
				continue;
			int size = var.getDomainSize();
			if (minIndex == -1 || minSize > size) {
				minIndex = i;
				minSize = size;
				if (size == 2)
					break;
			}
			// TO DO add random tie break
		}
		return minIndex;
	}

}