javax.constraints.impl.search.selectors.VarSelectorRandom Maven / Gradle / Ivy
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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
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//=============================================
// 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 randomly selects an unbound constrained
* variable from a given array of variables.
*/
import java.util.Random;
import javax.constraints.SearchStrategy;
import javax.constraints.VarSelectorType;
public class VarSelectorRandom extends AbstractVarSelector {
Random rn;
public VarSelectorType getType() {
return VarSelectorType.RANDOM;
}
/**
* Constructor from the Var[]
*/
public VarSelectorRandom(SearchStrategy strategy) {
super(strategy);
rn = new Random();
}
/**
* Returns the index of a randomly selected variable.
* If no variables to select, it returns -1;
*/
public int select() {
int[] unboundIndexes = new int[getVars().length];
int n = 0;
for(int i=0; i < getVars().length; i++) {
if (getVars()[i].isBound())
continue;
unboundIndexes[n++] = i;
}
if (n==0)
return -1;
if (n==1)
return unboundIndexes[0];
else {
int randomIndex = rn.nextInt(n); // return a value from 0 to n-1
return unboundIndexes[randomIndex];
}
}
}