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Introduction

Constrained network models can be used to describe a wide variety of real-world applications ranging from production, inventory, and distribution problems to financial applications. These problems can be solved with the NETFLOW procedure.

These models are conceptually easy since they are based on network diagrams that represent the problem pictorially. PROC NETFLOW accepts the network specification in a format that is particularly suited to networks. This not only simplifies problem description but also aids in the interpretation of the solution.

Certain algebraic features of networks are exploited by a specialized version of the simplex method so that solution times are reduced. Another optimization algorithm, the interior point algorithm, has been implemented in PROC NETFLOW and can be used as an alternative to the simplex algorithm to solve network problems.

Should PROC NETFLOW detect there are no arcs and nodes in the model's data, (that is, there is no network component), it assumes it is dealing with a linear programming (LP) problem. The interior point algorithm is automatically selected to perform the optimization.

You can also solve LP problems by using the OPTLP procedure. The OPTLP procedure requires a linear program to be specified by using a SAS data set that adheres to the MPS format, a widely accepted format in the optimization community. You can use the MPSOUT= option in the NETFLOW procedure to convert typical PROC NETFLOW format data sets into MPS-format SAS data sets.