MULTISTAGE is a program for optimizing cyclic schedules of multiproduct continuous plants according to Jose M.Pinto and Ignacio E.Grossmann in "Optimal Scheduling of Multistage Multiproduct Continuous Plants", Computers and Chemical Engineering, 9, 797-816 (1994).
These are multistage plants which consist of a sequence of stages each involving one production line that are interconnected by storage tanks.The basic model is Mixed Integer Nonlinear Programming (MINLP).
Multistage works through the use of different menus; it is flexible and easy to use. Given the data of the problem, MULTISTAGE creates a new GAMS file containing the model equations and optimizes the problem using the outer approximation code DICOPT++, and plot the Gantt Chart for the optimal assignments of products to stages.
DICOPT++ (DIscrete and Continuos OPTimizer) was developed by J.Viswanathan and Ignacio E.Grossmann at the Engineering Research Center (EDRC) of the Carnegie Mellon University. It is based on the extensions of the outer- approximation algorithm for the equality relaxation strategy.The code MINOS is used for solving the NLP subproblem and OSL is used for solving the MILP master problem in this model.