Controlled rounding of tabular data

Controlled rounding is a procedure that perturbs tabular data collected from respondents in such a way as to preserve the anonymity of the respondents while maintaining the integrity of the data. The three-dimensional controlled rounding problem is NP-complete. This paper describes a binary tree search algorithm for solving three-dimensional problems based on linear programming techniques. Computational results obtained from tests with over 31000 randomly generated tables and 292 real-life tables have shown that this algorithm can effectively find controlled roundings when they exist or determine that no solution exists. The computational results also demonstrate that the running time of the search algorithm can be cut in half by using a heuristic for initializing the simplex basis for the linear programming problems.