javax.constraints.impl.constraint.ConstraintMax 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

There is a newer version: 2.3.1

Show 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.constraint;


import javax.constraints.Var;
import javax.constraints.impl.AbstractConstraint;
import javax.constraints.impl.AbstractProblem;


/**
 * This is a linear constraints for a constrained integer variable that is equal to the maximal
 * variable in the array "vars" when they are all instantiated.
 */
public class ConstraintMax extends AbstractConstraint {

	String oper;
	Var[] vars;
	Var var;
	int value;
	Var maxVar;

	public ConstraintMax(Var[] vars, String oper, Var var) {
		super(vars[0].getProblem());
		this.vars = vars;
		this.oper = oper;
		this.var = var;
		createMaxVar();		
	}
	
	public ConstraintMax(Var[] vars, String oper, int value) {
		super(vars[0].getProblem());
		this.vars = vars;
		this.oper = oper;
		this.var = null;
		this.value = value;
		createMaxVar();		
	}
	
	void createMaxVar() {
		AbstractProblem p = (AbstractProblem)getProblem();
		int min = vars[0].getMin(); // the largest minimum
		int max = vars[0].getMax(); // the largest maximum
		for (int i = 1; i < vars.length; i++) {
			int mini = vars[i].getMin();
			int maxi = vars[i].getMax();
			if (min < mini)
				min = mini;
			if (max < maxi)
				max = maxi;
		}
		maxVar = p.variable("MaxArray", min, max);
		Var[] equalities = new Var[vars.length];
		for (int i = 0; i < vars.length; i++) {
			p.post(maxVar, ">=", vars[i]);
			equalities[i] = p.linear(maxVar,"=",vars[i]).asBool();
		}
		p.post(equalities, ">=", 1);
	}
	
	public void post() {
		if (var == null)
			getProblem().post(maxVar, oper, value);
		else 
			getProblem().post(maxVar, oper, var);
	}
	
	public Var getMaxVar() {
		return maxVar;
	}
	
}