predicate fzn_disjunctive_opt_reif(array[int] of var opt int: s,
                               array[int] of var int: d,
                               var bool: b) =
          b <-> forall (i,j in index_set(d) where i<j) (
            absent(s[i]) \/ absent(s[j]) \/
            d[i]=0 \/ d[j]=0 \/
            deopt(s[i])+d[i] <= deopt(s[j]) \/
            deopt(s[j])+d[j] <= deopt(s[i])
          );