Gabriele Di Stefano

Learn More
In this paper we provide efficient robust algorithms for shunting problems concerning the reordering of train cars over a hump. In particular, we study algorithms able to cope with small disruptions, as temporary and local unavailability and/or malfunctioning of key resources that can occur and affect planned operations. To this aim, a definition of robust(More)
We propose a fully-dynamic distributed algorithm for the all-pairs shortest paths problem on general networks with positive real edge weights. If ∆σ is the number of pairs of nodes changing the distance after a single edge modification σ (insert, delete, weight decrease, or weight increase) then the message complexity of the proposed algorithm is O(n∆σ) in(More)
Parity graphs form a superclass of bipartite and distance-hereditary graphs. Since their introduction, all the algorithms proposed as solutions to the recognition problem and other combinatorial problems exploit the structural property of these graphs described by Burlet and Uhry in [8]. This paper introduces a different structural property of parity(More)
Partitioning a permutation into a minimum number of monotone subsequences is NP-hard. We extend this complexity result to minimum partitioning into k-modal subsequences; here unimodal is the special case k = 1. Based on a network flow interpretation we formulate both, the monotone and the k-modal version, as mixed integer programs. This is the first(More)
The paper deals with a recent model of robot-based computing which makes use of identical, memoryless mobile robots placed on nodes of anonymous graphs. The robots operate in Look-Compute-Move cycles; in one cycle, a robot takes a snapshot of the current configuration (Look), takes a decision whether to stay idle or to move to one of its adjacent nodes(More)
Several attempts have been done in the literature in the last years in order to provide a formal definition of the notions of robustness and recoverability for optimization problems. Recently, a new model of recoverable robustness has been introduced in the context of railways optimization. The basic idea of recoverable robustness is to compute solutions(More)
A set of robots arbitrarily placed on different nodes of an anonymous ring have to meet at one common node and there remain. This problem is known in the literature as the gathering. Anonymous and oblivious robots operate in Look–Compute–Move cycles; in one cycle, a robot takes a snapshot of the current configuration (Look), decides whether to stay idle or(More)