Quadratic assignment problem
From Glossary
(QAP). See assignment problem.
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Assignment problem |
Choose an assignment of people to jobs so as to minimize total cost. The ordinary model is that of a matching problem. Although the usual assignment problem is solvable in polynomial time (as a linear program), important extensions are the following NP-complete problems:
- Quadratic assignment (QAP). The objective is a quadratic form, which can have just cross terms, so it need not be convex (in fact, it can be quasiconcave, in which case a solution occurs at an extreme point). The QAP includes the traveling salesman problem as a special case (this is what is used with a neural network model of the TSP).
- Multi-dimensional assignment. More than 2 indexes, the variables are of the form, . The constraints sum all but one index -- for example, the 3-index assignment problem is