Numerous algorithms are sensitive to the order in which PROC OPTGRAPH reads the data. If the order of the nodes or links is changed, either by you or by some parameter setting, the final result might change. In some cases, this difference is simply a permutation of identifiers (for example, connected components). In other cases, when using local optimization (for example, community detection) or discrete branching decisions (for example, traveling salesman problem), the final result might be a local (or alternative) solution. Two parameters that could have such an effect are STANDARDIZED_LABELS and NTHREADS=. Both of these options can change the internal order of the nodes and links.