[BUG] Exponential performance dropoff in addClauses with increasing number of AND subclauses in OR

[jpd236]

Describe the bug
When creating a clause of the form LogOp.or(LogOp.and(a, b), LogOp.and(c, d), ...) and adding it via Model#addClauses, the performance drops off exponentially.

I don't encounter the same performance issue when building an equivalent expression with a.and(b).or(c.and(d).or(...)).

To Reproduce
Here is some toy code that reproduces the issue. On my laptop, I start to see exponential increases in elapsed time around 10 AND clauses, and stop seeing progress above 17 AND clauses.

import org.chocosolver.solver.Model;
import org.chocosolver.solver.constraints.nary.cnf.LogOp;
import org.chocosolver.solver.variables.IntVar;

public class ChocoIssue {
    public static void main(String[] args) {
        Model m = new Model();
        IntVar[] vars = m.intVarArray(2, 1, 2);
        for (int i = 1; i < 100; i++) {
            LogOp[] ops = new LogOp[i];
            for (int j = 0; j < ops.length; j++) {
                ops[j] = LogOp.and(vars[0].eq(1).decompose().reify(), vars[1].eq(2).decompose().reify());
            }
            long startTime = System.nanoTime();
            m.addClauses(LogOp.or(ops));
            long endTime = System.nanoTime();
            System.out.println("Elapsed time for " + i + " clauses = " + (endTime - startTime));
        }
    }
}

Expected behavior
Since both approaches appear to be logically equivalent, I'd expect performance to be about the same. That said, I admit I'm a novice with this library and may absolutely be missing something silly that I'm doing here.

Environment (please complete the following information):

• Choco-solver version: 4.10.7
• JRE : 8