By default Calc in Apache Office ships with a solver engine for linear programming only. This allows the optimization of models to a certain degree. However, if the formulas or constraints become more complex, nonlinear programming is required. That missing gap is now filled by the NLPSolver extension (developed by Sun Microsystems Inc).
It incorporates two cooperative group optimization algorithms, SCO and DEPSO, which can handle continuous and integer variables as well as nonlinear constraints. For more information about their usage, please refer to here.
Both algorithms include work from Dr. Xie, who did a lot of research in this area.