AllDifferent OnlyEnforceIf doesn't work as expected

[Daniel Karapetyan]

Hi,

I am trying to implement a constraint that ensures that at least two of the three variables have different values (in general, I need to ensure that at least k out of n variables have different values).  I tried the following code but it incorrectly tells me that the problem is unsat.  Replacing AddAllDifferent([x, y]) with Add(x != y) fixed the issue but it's hard (and I assume inefficient) to generalise to larger n's.

    model = cp_model.CpModel()
    s1 = model.NewIntVar(1, 5, 's1')
    s2 = model.NewIntVar(1, 5, 's2')
    s3 = model.NewIntVar(1, 5, 's3')

    v1 = model.NewBoolVar('v1')
    v2 = model.NewBoolVar('v2')
    v3 = model.NewBoolVar('v3')

    # This constraint is added for testing purposes; a feasible solution is s1 = s2 = 1 and s3 = 2
    model.Add(s1 == s2)

    model.AddAllDifferent([s1, s2]).OnlyEnforceIf(v1)
    model.AddAllDifferent([s2, s3]).OnlyEnforceIf(v2)
    model.AddAllDifferent([s1, s3]).OnlyEnforceIf(v3)
           
    model.AddBoolOr([v1, v2, v3])

    solver = cp_model.CpSolver()
    status = solver.Solve(model)

Am I not allowed to use AllDifferent with OnlyEnforceIf?

Thank you,

Daniel.

[Laurent Perron]

Enforcement is only supported on linear equations, bool and, bool or and intervals.

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[Daniel Karapetyan]

I see, thank you Laurent!