An Improved Integer L-Shaped Method for the Vehicle Routing Problem with Stochastic Demands

We present an improved integer L-shaped method for the vehicle routing problem with stochastic demands. It exhibits speedups up to a factor of 325 compared with the current state-of-the-art, which allows us to solve 153 previously unsolved benchmark instances to optimality. The algorithm builds on the state-of-the-art in a few ways. First, we rectify a few technical issues found in the current literature. Second, we improve valid inequalities known as partial route inequalities. Finally, we introduce three new types of valid inequalities.