28 research outputs found
Analysing local algorithms in location-aware quasi-unit-disk graphs
A local algorithm with local horizon r is a distributed algorithm that runs in r synchronous communication rounds; here r is a constant that does not depend on the size of the network. As a consequence, the output of a node in a local algorithm only depends on the input within r hops from the node. We give tight bounds on the local horizon for a class of local algorithms for combinatorial problems on unit-disk graphs (UDGs). Most of our bounds are due to a refined analysis of existing approaches, while others are obtained by suggesting new algorithms. The algorithms we consider are based on network decompositions guided by a rectangular tiling of the plane. The algorithms are applied to matching, independent set, graph colouring, vertex cover, and dominating set. We also study local algorithms on quasi-UDGs, which are a popular generalisation of UDGs, aimed at more realistic modelling of communication between the network nodes. Analysing the local algorithms on quasi-UDGs allows one to assume that the nodes know their coordinates only approximately, up to an additive error. Despite the localisation error, the quality of the solution to problems on quasi-UDGs remains the same as for the case of UDGs with perfect location awareness. We analyse the increase in the local horizon that comes along with moving from UDGs to quasi-UDGs.Peer reviewe
Bribeproof mechanisms for two-values domains
Schummer (Journal of Economic Theory 2000) introduced the concept of
bribeproof mechanism which, in a context where monetary transfer between agents
is possible, requires that manipulations through bribes are ruled out.
Unfortunately, in many domains, the only bribeproof mechanisms are the trivial
ones which return a fixed outcome.
This work presents one of the few constructions of non-trivial bribeproof
mechanisms for these quasi-linear environments. Though the suggested
construction applies to rather restricted domains, the results obtained are
tight: For several natural problems, the method yields the only possible
bribeproof mechanism and no such mechanism is possible on more general domains.Comment: Extended abstract accepted to SAGT 2016. This ArXiv version corrects
typos in the proofs of Theorem 7 and Claims 28-29 of prior ArXiv versio
Passenger-Centric Urban Air Mobility: Fairness Trade-Offs and Operational Efficiency
Urban Air Mobility (UAM) has the potential to revolutionize transportation.
It will exploit the third dimension to help smooth ground traffic in densely
populated areas. To be successful, it will require an integrated approach able
to balance efficiency and safety while harnessing common resources and
information. In this work we focus on future urban air-taxi services, and
present the first methods and algorithms to efficiently operate air-taxi at
scale. Our approach is twofold. First, we use a passenger-centric perspective
which introduces traveling classes, and information sharing between transport
modes to differentiate quality of services. This helps smooth multimodal
journeys and increase passenger satisfaction. Second, we provide a flight
routing and recharging solution which minimizes direct operational costs while
preserving long term battery life through reduced energy-intense recharging.
Our methods, which surpass the performance of a general state-of-the-art
commercial solver, are also used to gain meaningful insights on the design
space of the air-taxi problem, including solutions to hidden fairness issues.Comment: Submitted to Transportation Research Part C: Emerging Technologie
Survey of local algorithms
A local algorithm is a distributed algorithm that runs in constant time, independently of the size of the network. Being highly scalable and fault-tolerant, such algorithms are ideal in the operation of large-scale distributed systems. Furthermore, even though the model of local algorithms is very limited, in recent years we have seen many positive results for non-trivial problems. This work surveys the state-of-the-art in the field, covering impossibility results, deterministic local algorithms, randomised local algorithms, and local algorithms for geometric graphs.Peer reviewe