The Traveling Purchaser Problem and its variants

The Traveling Purchaser Problem (TPP) has been one of the most studied generalizations of the Traveling Salesman Problem. In recent decades, the TPP attracted the attention of both researchers in combinatorial optimization and practitioners, thanks to its double nature of procurement and transportation problem. The problem has been used to model several application contexts and is computationally challenging, dealing at the same time with the suppliers selection, the optimization of the purchasing plan and the routing decisions of the purchaser. For the first time after 50 years from its birth, we survey all the research done on the TPP including the most interesting and best performing solution methods proposed so far. We conclude providing some interesting future developments.