Z3 negate maximisation objective #786
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ThomSerg
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As encountered during the last two XCSP3 competitions, Z3 internally negates the objective function when maximising (turning the problem into minimisation). But when calling
sol.evaluate(obj).as_long()to get the objective value after a solve call, this abstraction gets broken and Z3 returns the negated value. This in turn resulted in incorrect values forsolver.objective_value(). Added code to undo the negation.