The Quadratic Assignment Problem (QAP) has remained one of the great challenges in combinatorial optimization. It is still considered a computationally nontrivial task to solve modest size problems, say of size n=25. The QAPLIB was first published in 1991, in order to provide a unified testbed for QAP, accessible to the scientific community. It consisted of virtually all QAP instances that were accessible to the authors at that time. Due to the continuing demand for these instances, and the strong feedback from many researchers, a major update was provided by Burkard, Karisch and Rendl in 1994. This update was also accessible through anonymous ftp. This update included many new problem instances, generated by several researchers for their own testing purposes. Moreover, a list of current champions, i.e. best known feasible solutions, and best lower bounds was included.
The update of April 1996 reflected on one hand the big changes in electronic communication. QAPLIB became a World Wide Web site, the QAPLIB Home Page. On the other hand, the update was necessary, due to the increased research activities around the QAP. A short list of at-that-time-recent dissertations concerning QAP, was included.
The update of June 2000 reflects the progress made on the QAP especially on solving new test instances and test instances which were previously not solved to optimality. It includes an updated list of people working on the QAP and an updated list of surveys and dissertations on the QAP.
The update of January 2002 reflects the progress made more recently on the QAP. The emphasis relies on the optimal solution of test instances which were previously not solved to optimality. The optimal solutions were obtained by using new bounding techniques and new branch and bound schemes generally implemented in very powerful parallel computation environments. This update also includes new test instances and some improvements on the best known solutions of existing test instances. The list of people working on the QAP as well the list of references have also been updated.
The web site will be updated on a regular basis and we hope that, with your help, the QAPLIB Home Page will be an up-to-date source for the QAP. We appreciate any hints on new and better solutions to existing instances or new test instances form QAPLIB, as well as any hints on recent literature pointers on the QAP.