[BUG] Start and end of tasks are always enforced at root #1119
Description
Hi,
I'm attempting to model a half-reified Cumulative constraint (see sample code below).
However, while the "non-overlapness" of the Cumulative constraints is correctly reified, the link between start and end variables in the tasks is not reified with it.
E.g., the model with constraints [e == 1, bv -> Cumulative([s], [3], [e], [1],[1])] should be satisfied when the Boolean variable is set to False.
However, as the task is created at the toplevel of the constraint model, it will fail because of the e == 1 assignment.
Is this considered the expected behaviour of the tasks-constructor? And if so, how should I modify my model to properly reflect a truely half-reified Cumulative constraint?
import org.chocosolver.solver.Model;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.BoolVar;
import org.chocosolver.solver.variables.Task;
public class CumulativeModel {
public static void main(String[] args) {
// Create a Choco model
Model model = new Model("Cumulative Scheduling Model");
// Define variables
IntVar[] start = new IntVar[3];
IntVar[] end = new IntVar[3];
int[] duration = {3, 3, 3};
IntVar[] demand = new IntVar[3];
IntVar capacity = model.intVar("cap", 1,1);
for (int i = 0; i < 3; i++) {
start[i] = model.intVar("start[" + i + "]", 0, 5);
end[i] = model.intVar("end[" + i + "]", 0, 5);
demand[i] = model.intVar("demand[" + i +"]", 1,1);
}
// Make the tasks
Task[] tasks = new Task[3];
for (int i = 0; i < 3; i++) {
tasks[i] = new Task(start[i], duration[i], end[i]);
}
// Define the Boolean variable
BoolVar bv = model.boolVar("bv");
// Add cumulative constraint wrapped in implication
model.cumulative(tasks, demand, capacity).impliedBy(bv);
// Add the constraint end[0] == 1
model.arithm(end[0], "=", 1).post(); // This makes the model UNSAT
// Solve the model
if (model.getSolver().solve()) {
System.out.println("Solution found:");
for (int i = 0; i < 3; i++) {
System.out.println("start[" + i + "] = " + start[i].getValue());
System.out.println("end[" + i + "] = " + end[i].getValue());
}
} else {
System.out.println("No solution found.");
}
}
}I'm running on the latest release (v4.10.17)
Kind regards,
Ignace