Fleet Size and Mix Split-Delivery Vehicle Routing
  In the classic Vehicle Routing Problem (VRP) a fleet of of vehicles has to
visit a set of customers while minimising the operations' costs. We study a
rich variant of the VRP featuring split deliveries, an heterogeneous fleet, and
vehicle-commodity incompatibility constraints. Our goal is twofold: define the
cheapest routing and the most adequate fleet.
  To do so, we split the problem into two interdependent components: a fleet
design component and a routing component. First, we define two Mixed Integer
Programming (MIP) formulations for each component. Then we discuss several
improvements in the form of valid cuts and symmetry breaking constraints.
  The main contribution of this paper is a comparison of the four resulting
models for this Rich VRP. We highlight their strengths and weaknesses with
extensive experiments.
  Finally, we explore a lightweight integration with Constraint Programming
(CP). We use a fast CP model which gives good solutions and use the solution to
warm-start our models.
