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package samples.real;
import samples.AbstractProblem;
import solver.Solver;
import solver.constraints.real.Ibex;
import solver.constraints.real.RealConstraint;
import solver.search.loop.monitors.SMF;
import solver.search.strategy.IntStrategyFactory;
import solver.variables.IntVar;
import solver.variables.RealVar;
import solver.variables.VariableFactory;
/**
* <a href="http://www.mozart-oz.org/documentation/fdt/node21.html">mozart-oz</a>:<br/>
* "A kid goes into a grocery store and buys four items. The cashier
* charges $7.11, the kid pays and is about to leave when the cashier
* calls the kid back, and says ''Hold on, I multiplied the four items
* instead of adding them; I'll try again; Hah, with adding them the
* price still comes to $7.11''. What were the prices of the four items?
* <p/>
* The model is taken from: Christian Schulte, Gert Smolka, Finite Domain
* Constraint Programming in Oz. A Tutorial. 2001."
* <br/>
* <p/>
* This problem deals with large domains which result in integer overflows with classical constraints.
* Thus, this example introduces a dedicated propagator which handles large value products.
*
* @author Charles Prud'homme, Jean-Guillaume Fages
* @since 08/08/11
*/
public class Grocery extends AbstractProblem {
IntVar[] itemCost;
RealVar[] realitemCost;
@Override
public void createSolver() {
solver = new Solver("Grocery");
}
@Override
public void buildModel() {
double epsilon = 0.000001d;
// 4 integer variables (price in cents)
itemCost = VariableFactory.boundedArray("item", 4, 1, 711, solver);
// views as real variables to be used by Ibex
realitemCost = VariableFactory.real(itemCost, epsilon);
solver.post(new RealConstraint("Sum", "{0} + {1} + {2} + {3} = 711", Ibex.COMPO, realitemCost));
solver.post(new RealConstraint("Product", "{0} * {1}/100 * {2}/100 * {3}/100 = 711", Ibex.HC4, realitemCost));
// symmetry breaking
solver.post(new RealConstraint("SymmetryBreaking","{0} <= {1};{1} <= {2};{2} <= {3}", Ibex.HC4, realitemCost));
}
@Override
public void configureSearch() {
// choco branching
SMF.log(solver, true, true);
solver.set(IntStrategyFactory.lexico_UB(itemCost));
// ibex branching
// solver.set(new AssignmentInterval(realitemCost, new Cyclic(realitemCost), new RealDomainMiddle()));
}
@Override
public void solve() {
solver.findSolution();
solver.getIbex().release();
}
@Override
public void prettyOut() {
System.out.println("*******");
int sum = 0;
long prod = 1;
for (int i = 0; i < 4; i++) {
sum += realitemCost[i].getUB();
prod *= itemCost[i].getValue();
System.out.println("item " + i + " : " + itemCost[i].getValue());
}
prod /= 1000000;
System.out.println("sum = " + sum + " instead of 711");
System.out.println("prod = " + prod + " instead of 711");
}
public static void main(String[] args) {
new Grocery().execute(args);
}
}