A mixed-integer optimization problem contains both continuous-valued and integer-valued decision variables. Continuous variables can take real-number values, while integer variables represent discrete choices such as selections, sequences, or assignments. section 2.1.1
This classification describes the decision variables, not the number of objectives, constraints, or the linearity of the problem. When discrete variables form sets, combinations, or permutations, the problem may also be combinatorial. section 2.1.1 section 2.5
Elevator operation
Optimizing elevator speed and acceleration uses continuous variables, while choosing the sequence in which passengers are picked up uses a discrete variable. Optimizing all of them together creates a mixed-integer optimization problem. section 2.1.1
Classify decision variables as follows:
- Use continuous optimization when variables take real-number values. section 2.1.1
- Use integer or discrete optimization when variables take integer values. section 2.1.1
- Use mixed-integer optimization when both variable types occur in the same problem. section 2.1.1
