Diagnose constraints

When you run Infeasibility Diagnosis with the Diagnose Constraints option selected, infeasibility diagnosis identifies individual constraints that are causing infeasibility. It populates the Constraint Summary output table and identifies which the set of all constraints that are conflicting with each other. This method can be used for nearly all Network Optimization problem, but it is particularly developed for identifying the set of “all” conflicting constraints. As an example, you have a model with a maximum production constraint that conflicts with another minimum production constraint. When you run this algorithm, you will see both constraints in the Constraint Summary output table. To set this option in a scenario item, select the “Diagnosis Type” Infeasibility Diagnosis Option and select Diagnose constraints as the value.

Upon completion of the infeasibility diagnosis, the Constraint Summary output table is displayed, filtered for those constraints that were detected as causing the infeasibility. You can review the Diagnostic Excess and Diagnostic Deficit values in the Constraint Summary table.

Assume a constraint such as:

Flow >= 100

The Diagnostic Excess is the amount needed to be added to the constraint value (left hand side of the equation) or alternatively be subtracted from the constraint requirement (right hand side of the equation).

Similarly:

Flow <= 100

The Diagnostic Deficit is the amount needed to be subtracted from the constraint value (left hand side of the equation) or alternatively be added to the constraint requirement (right hand side of the equation).

Consider the following two examples: