How to model special set constraints using Choco solver framework for Java

Question

I'm having problems modelling a problem and solving it with Choco-solver in Java, and I am not that familiar with constraint programming to begin with, but have been tasked to make a seating app for conferences where:

• Each table must have a minimum of 6 people, and there are always enough tables.
• People should be seated with neighbors as to maximize shared interests.
• On preceding days we want to minimize people being seated on tables with people they were seated with earlier.
• People are either of class A or B, and we want to minimize occurrences of class A on each table.

So far we have a SetVar guest_list including 1 up to number of guests. then partition guest_list to SetVar[] tables.

But how do I make constraints saying that each table.size >= 6?

How do I make constraints between two sets, as to minimize membership/intersections?

And I have no idea how to model for neighbors within a set as to maximize shared interests.

import org.chocosolver.solver.Model;
import org.chocosolver.solver.Solution;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.SetVar;

// constant value declarations
int number_of_guests = 100;
int table_size = 8;
int tables_needed = number_of_guests / table_size + 1;

// this will later be passed as argument, generated for testing
int[] guest_ids = new int[number_of_guests];
for (int i = 0; i < number_of_guests; i++) {
    guest_ids[i] = i;
}

// Model and variables
Model model = new Model("Seating solver");

IntVar min_guests_at_tables = model.intVar(6);
// a list containing all guests in its LB
SetVar guest_list  = model.setVar("guests", guest_ids);
// making empty sets for each table needed, UB is all guests
SetVar[] tables = model.setVarArray(tables_needed, new int[]{}, guest_ids);
// log over table seatings from earlier days, starts empty for day 1.
// want to minimize how many members from tables[x] share with any ser of logged_tables
SetVar[] logged_tables = model.setVarArray(0, new int[]{}, new int[]{});
// a setvar of all interests for each guest, will be imported later.
SetVar[] guest_interests = model.setVarArray(number_of_guests, new int[]{}, new int[]{});
// set of all those members of group A
// random test values inserted
SetVar group_A_members = model.setVar(1,23,54,2);

// Constraints unsure about all of these

// each set must be unique
model.allDifferent(tables);
for (SetVar table : tables) {
    // TODO trying to constrain sizes of each table set to 6 or greater
    model.arithm(model.intVar(table.getLB().size()), ">=", min_guests_at_tables);
// TODO trying to minimize number of shared members in tables, with whats in logged_tables
for (SetVar old_table : logged_tables) {
    // no idea
}
// TODO trying to maximize the amount of interest neigbors in a set share
// no idea

// TODO minimize shared members from table with group_A_members
// no idea how to minimize or maximize
}

// Solving

Solution s = model.getSolver().findSolution();
if (s != null) System.out.println(s.toString());

Answer 1

The set of available constraints is accessible from model, which implements IConstraintFactory. Look at ISetConstraintFactory.java in the source code. There are constraints related to set sizes, unions, partitions...