Facility location problem is one of the most famous branches of operational research which is used to find the best location for establishing the facilities. Congested facility location problem is a subcategory of facility location problems in which customers have to wait in a queue in order to receive the service. In this type of location problems, in addition to finding the best location for facilities, the number of assigned servers to each facility should be optimized to minimize the customer’s aggregate waiting time or the server’s idle time. Since the location problems are known as NP-hard problems on a general graph, this study aims to develop a combined simulated annealing algorithm to improve the quality of solution based on the location and number of servers simultaneously.
