Browsing by Subject "Quadratic Assignment Problem"

Now showing 1 - 4 of 4

Open Access
A branch-and-cut algorithm for quadratic assignment problems based on linearizations
(Elsevier, 2007-04) Erdoğan, G.; Tansel, B.
The quadratic assignment problem (QAP) is one of the hardest combinatorial optimization problems known. Exact solution attempts proposed for instances of size larger than 15 have been generally unsuccessful even though successful implementations have been reported on some test problems from the QAPLIB up to size 36. In this study, we focus on the Koopmans–Beckmann formulation and exploit the structure of the flow and distance matrices based on a flow-based linearization technique that we propose. We present two new IP formulations based on the flow-based linearization technique that require fewer variables and yield stronger lower bounds than existing formulations. We strengthen the formulations with valid inequalities and report computational experience with a branch-and-cut algorithm. The proposed method performs quite well on QAPLIB instances for which certain metrics (indices) that we proposed that are related to the degree of difficulty of solving the problem are relatively high (⩾0.3⩾0.3). Many of the well-known instances up to size 25 from the QAPLIB (e.g. nug24, chr25a) are in this class and solved in a matter of days on a single PC using the proposed algorithm.
Open Access
A polyhedral approach to quadratic assignment problem
(1994) Köksaldı, Ahmet Sertaç Murat
In this thesis, Quadratic Assignment Problem is considered. Since Quadratic Assignment Problem is JVP-bard, no polynomial time exact solution method exists. Proving optimality of solutions to Quadratic Assignment Problems has been limited to instances of small dimension. In this study, Quadratic Assignment Problem is handled from a polyhedral point of view. A graph theoretic formulation of the problem is presented. Later, Quadratic Assignment Polytope is defined and subsets of valid equalities and inequalities for Quadratic Assignment Polytope is given. Finally, results of the experiments with a polyhedral cutting plane algorithm using the new formulation is also presented.
Open Access
Quadratic assignment problem : linearizations and polynomial time solvable cases
(2006) Erdoğan, Güneş
The Quadratic Assignment Problem (QAP) is one of the hardest combinatorial optimization problems known. Exact solution attempts proposed for instances of size larger than 15 have been generally unsuccessful even though successful implementations have been reported on some test problems from the QAPLIB up to size 36. In this dissertation, we analyze the binary structure of the QAP and present new IP formulations. We focus on “flow-based” formulations, strengthen the formulations with valid inequalities, and report computational experience with a branch-and-cut algorithm. Next, we present new classes of instances of the QAP that can be completely or partially reduced to the Linear Assignment Problem and give procedures to check whether or not an instance is an element of one of these classes. We also identify classes of instances of the Koopmans-Beckmann form of the QAP that are solvable in polynomial time. Lastly, we present a strong lower bound based on Bender’s decomposition.
Open Access
Two classes of quadratic assignment problems that are solvable as linear assignment problems
(Elsevier, 2011) Erdoǧan, G.; Tansel, B. Ç.
The Quadratic Assignment Problem is one of the hardest combinatorial optimization problems known. We present two new classes of instances of the Quadratic Assignment Problem that can be reduced to the Linear Assignment Problem and give polynomial time procedures to check whether or not an instance is an element of these classes.