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package solver.search.strategy.strategy;
import solver.search.strategy.assignments.DecisionOperator;
import solver.search.strategy.decision.Decision;
import solver.search.strategy.decision.fast.FastDecision;
import solver.search.strategy.selectors.IntValueSelector;
import solver.search.strategy.selectors.VariableSelector;
import solver.variables.IntVar;
import util.PoolManager;
/**
* Class to perform branching decisions over integer variables
* <br/>
*
* @author Charles Prud'homme, Jean-Guillaume Fages
* @since 2 juil. 2010
*/
public class IntStrategy extends AbstractStrategy<IntVar> {
// Search strategy parameters
VariableSelector<IntVar> variableSelector;
IntValueSelector valueSelector;
DecisionOperator<IntVar> decisionOperator;
// object recycling management
PoolManager<FastDecision> decisionPool;
/**
* Creates a search strategy which selects a variable X and a value V to perform
* the decision X = V
*
* BEWARE: if the variable domain is not enumerated, the value V should be a domain bound.
* Otherwise, the decision cannot be negated, and the search may loop infinitely.
*
* @param scope defines which variables to branch on
* @param varSelector defines how to select the next variable to branch on
* @param valSelector defines how to select the value involved in the branching decision
*/
public IntStrategy(IntVar[] scope, VariableSelector<IntVar> varSelector, IntValueSelector valSelector) {
this(scope, varSelector, valSelector,DecisionOperator.int_eq);
}
/**
* Creates a search strategy which selects a variable X and a value V to perform
* the decision X decOperator V
*
* This can be X <= V for instance.
*
* BEWARE: if the variable domain is not enumerated, and if the operator is either "=" or "!=",
* then the value V should be a domain bound. Otherwise, the decision cannot be negated,
* and the search may loop infinitely.
*
* @param scope defines which variables to branch on
* @param varSelector defines how to select the next variable to branch on
* @param valSelector defines how to select the value involved in the branching decision
* @param decOperator defines what to do in a branching decision
*/
public IntStrategy(IntVar[] scope, VariableSelector<IntVar> varSelector, IntValueSelector valSelector,
DecisionOperator<IntVar> decOperator) {
super(scope);
this.variableSelector = varSelector;
this.valueSelector = valSelector;
this.decisionOperator = decOperator;
this.decisionPool = new PoolManager<>();
}
@Override
public void init() {}
@Override
public Decision<IntVar> computeDecision(IntVar variable) {
if (variable == null || variable.isInstantiated()) {
return null;
}
int value = valueSelector.selectValue(variable);
FastDecision d = decisionPool.getE();
if (d == null) {
d = new FastDecision(decisionPool);
}
d.set(variable, value, decisionOperator);
return d;
}
@SuppressWarnings({"unchecked"})
@Override
public Decision getDecision() {
IntVar variable = variableSelector.getVariable(vars);
return computeDecision(variable);
}
}