predicate pareto_optimal(var int: obj1, var int: obj2) =
	let {
		int: ms = 1000;   % max solutions
		var 0..ms: nsol;  % number of solutions
		set of int: SOL = 1..ms;
		array[SOL] of var lb(obj1)..ub(obj1): s1;
		array[SOL] of var lb(obj2)..ub(obj2): s2;
	} in if status() = START then
		nsol = 0
	elseif status() = UNSAT then
		complete()        % we are finished!
	elseif status() = SAT then
		nsol = sol(nsol) + 1 /\
		s1[nsol] = sol(obj1) /\
		s2[nsol] = sol(obj2)
	endif
	/\ for(i in 1..nsol) (
		obj1 < lastval(s1[i]) \/ obj2 < lastval(s2[i])
	) /\ for(i in 1..ms) (
		if i in 1..nsol-1 then
			s1[i] = lastval(s1[i]) /\ 
			s2[i] = lastval(s2[i]) /\ 
		elsif i = nsol /\ status() != SAT then
			s1[i] = lastval(s1[i]) /\ 
			s2[i] = lastval(s2[i]) /\ 
		elseif i in nsol+1..ms then
			s1[i] = lb(obj1) /\
			s2[i] = lb(obj2)
		endif
	);