If you are familiar with linear programming theory, then you recall that a linear programming problem can be stated in primal or dual form, and an optimal solution (if one exists) of the dual has a direct relationship to an optimal solution of the primal model. ILOG CPLEX Dual Simplex Optimizer makes use of this relationship, but still reports the solution in terms of the primal model. The dual simplex method is the first choice for optimizing a linear programming problem, especially for primal-degenerate problems with little variability in the righthand side coefficients but significant variability in the cost coefficients.