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2. Implementing a Mathematical Formulation

You should approach the building of an LP model using Aspen SCM Planning as you would the building of any other LP model. That is, you should start by working out the mathematical formulation using pencil and paper. See Algebraic Formulation for advice as to how to identify and document a mathematical formulation.

The components of a mathematical formulation and their corresponding entities in an Aspen SCM Planning model are:

Mathematical Formulation Aspen SCM Planning
Subscripts User-defined sets which index generic rows and columns and are specified as generic fields in ROWS(*,FLD2–FLD6) or COLS(*,FLD2–FLD6)
Sets Subsets of the sets which correspond to subscripts; may also be implemented as user-defined incidence tables
Constants User-defined tables indexed by the sets which correspond to subscripts
Decision Variables Generic columns are defined in COLS
Nature of the column (UP, UI, BV, etc) defined in POLI(*,MIN)
Objective Function CST column in POLI
Constraints Generic rows are defined in ROWS
Nature of the row (E, L, G) defined in POLI(*,MIN)
Coefficients of generic columns in generic rows are defined in COEF
Right hand sides are defined in POLI(*,MAX)
Bounds Usually specified in POLI(*,MIN) and POLI(*,MAX). POLI(*,MIN) is also used to specify some variable types, e.g. FR, UI, BV, SC. In these cases the more important bound is specified as POLI(*,MAX) and the other has to be written into the generated matrix by bespoke code.


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