Question

what does it mean to ”define decision variables” (this is more vague, but is mostly what went wrong)

Answer 1

Defining decision variables. A decision variable is a quantity that the decision-maker controls. For example, in an optimization model for labor scheduling, the number of nurses to employ during the morning shift in an emergency room may be a decision variable.

Decision variables are added to an optimization problem by instantiating a decision variable and adding the instance to the optimization using the COptQuestOptimization::AddVariable() method.

You can optionally assign a name to a decision variable and the variable names can be used in string expressions for defining a COptQuestStringObjective or a COptQuestStringConstraint. If the variable name contains special characters such as blanks, enclose the variable name in square brackets when creating the string expression. For example, "2500*[Machine 1] + 3000 * [Machine 2] <= 100000".