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18153
20/06/2018

A Study of Evacuation Planning for Wildfires

C.ARTIGUES, E.HEBRARD, Y.PENCOLE, A.SCHUTT, P.STUCKEY

ROC, DISCO, CSIRO, Univ of Melbourne

Rapport LAAS N°18153, Juin 2018, 17p.

Lien : https://hal.archives-ouvertes.fr/hal-01814083

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Abstract

The GEO-SAFE project gathers researchers and fire emergency practitioners from EU and Australia with the aim to design innovative models and efficient response tools based on optimization methods for fighting wildfires. In this paper, we consider an evacuation planning problem issued from discussions with practitioners, where a wildfire is threatening a region with intermediate populated centres. As in earlier approaches in case of flood, we use a constraint optimization model involving malleable tasks to represent the evacuation of a population and a cumulative constraint per route segments. Indeed, in order to mitigate congestion risks, the authorities may delay the start of the evacuation but they may also affect the rate of evacuation by modulating the method used to raise the alarm. However, we consider a different objective: we maximize the minimum " safety margin " , weighted by the population, over every road segment. We introduce a new heuristic and a global flow constraint propa-gator. Moreover, we also propose an instance generator based on a random generation of road networks and basic fire propagation models. This generator produces challenging benchmarks even with very few evacuation tasks. Finally, we report the results of extensive computational experiments done using CP Optimizer.

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18154
20/06/2018

GeoSafe – Evacuation planning problems

C.ARTIGUES, E.HEBRARD, Y.PENCOLE, A.SCHUTT, P.STUCKEY

ROC, DISCO, CSIRO, Univ of Melbourne

Rapport LAAS N°18154, Juin 2018, 10p.

Lien : https://hal.archives-ouvertes.fr/hal-01814177

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Abstract

This paper aims at identifying new challenging variants of the evacuation planning problems, especially in case of bush fires, based on exchanges with practitioners in the context of the GeoSafe project. A large amount of work has been carried out at NICTA mainly in the context of floodings, which can be easily transposed to evacuation in case of fires. .We present a state-of-the-art review of these papers and we provide new research directions for the GeoSafe project.

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18155
20/06/2018

Data Instance generator and optimization models for evacuation planning in the event of wildfire

C.ARTIGUES, E.HEBRARD, Y.PENCOLE, A.SCHUTT, P.STUCKEY

ROC, DISCO, CSIRO, Univ of Melbourne

Rapport LAAS N°18155, Juin 2018, 18p.

Lien : https://hal.archives-ouvertes.fr/hal-01814063

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Abstract

One critical part of decision support during the response phase to a wildfire is the ability to perform large-scale evacuation planning. While in practice most evacuation planning is principally designed by experts using simple heuristic approaches or scenario simulations, more recently optimization approaches to evacuation planning have been carried out, notably in the context of floodings. Evacuation planning in case of wildfires is much harder as wildfire propagations are inherently less predictable than floods. This paper present a new optimization model for evacuation planning in the event of wildfire aiming at maximizing the temporal safety margin between the evac-uees and the actual or potential wildfire front. As a first contribution, an open-source data instance generator based on road network generation via quadtrees and a basic fire propagation model is proposed to the community. As a second contribution we propose 0–1 integer programming and constraint programming formulations enhanced with a 1 simple compression heuristic that are compared on 240 problem instances build by the generator. The results show that the generated instances are computationally challenging and that the contraint programming framework obtains the best performance.

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18094
20/06/2018

SRide: A Privacy-Preserving Ridesharing System

U.M.AIVODJI, K.HUGUENIN, M.J.HUGUET, M.O.KILLIJIAN

TSF, HEC Lausanne, ROC

Manifestation avec acte : ACM Conference on Security and Privacy in Wireless and Mobile Networks ( WiSec ) 2018 du 18 juin au 20 juin 2018, Stockholm (Suède), Juin 2018 , N° 18094

Lien : https://hal.archives-ouvertes.fr/hal-01762436

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143253
18142
11/06/2018

Octal Games on Graphs: The game 0.33 on subdivided stars and bistars. Full proof of Theorem 22

L.BEAUDOU, P.COUPECHOUX, A.DAILLY, S.GRAVIER, J.MONCEL, A.PARREAU, E.SOPENA

UBP, ROC, LIRIS, UJF, LABRI

Rapport LAAS N°18142, Juin 2018, 16p.

Lien : https://hal.archives-ouvertes.fr/hal-01807116

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Abstract

We give a full proof of Theorem 22 of "Octal Games on Graphs: The game 0.33 on subdivided stars and bistars".

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18120
22/05/2018

Optimal convergence rates for Nesterov acceleration

J.F.AUJOL, C.DOSSAL, A.RONDEPIERRE

IMB, IMT, Toulouse, ROC

Rapport LAAS N°18120, Mai 2018, 16p.

Lien : https://hal.archives-ouvertes.fr/hal-01786117

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Abstract

In this paper, we study the behavior of solutions of the ODE associated to Nesterov acceleration. It is well-known since the pioneering work of Nesterov that the rate of convergence O(t 2) is optimal for the class of convex functions. In this work, we show that better convergence rates can be obtained with some additional geometrical conditions, such as Lojasiewicz property. More precisely, we prove the optimal convergence rates that can be obtained depending on the geometry of the function F to minimize. The convergence rates are new, and they shed new light on the behavior of Nesterov acceleration schemes.

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18098
20/04/2018

Multi-skill project scheduling in a nuclear research facility

O.POLO MEJIA, M.C.ANSELMET, C.ARTIGUES, P.LOPEZ

CEA Cadarache, ROC

Manifestation avec acte : International Conference on Project Management and Scheduling ( PMS ) 2018 du 17 avril au 20 avril 2018, Rome (Italie), Avril 2018 , N° 18098

Lien : https://hal-cea.archives-ouvertes.fr/cea-01780570

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18159
13/04/2018

Online firefighting on trees

P.COUPECHOUX, M.DEMANGE, D.ELLISON, B.JOUVE

ROC, RMIT, IMT, Toulouse

Manifestation avec acte : International Symposium on Combinatorial Optimization ( ISCO ) 2018 du 11 avril au 13 avril 2018, Marrakech (Maroc), Avril 2018, 13p. , N° 18159

Lien : https://hal.archives-ouvertes.fr/hal-01815768

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Abstract

In the Firefighter problem, introduced by Hartnell in 1995, a fire spreads through a graph while a player chooses which vertices to protect in order to contain it. In this paper, we focus on the case of trees and we consider as well the Fractional Firefighter game where the amount of protection allocated to a vertex lies between 0 and 1. We introduce the online version of both Firefighter and Fractional Firefighter, in which the number of firefighters available at each turn is revealed over time. We show that the greedy algorithm on finite trees, which maximises at each turn the amount of vertices protected, is 1/2-competitive for both online versions; this was previously known only in special cases of Firefighter. We also show that, for Firefighter, the optimal competitive ratio of online algorithms ranges between 1/2 and the inverse of the golden ratio. The greedy algorithm is optimal if the number of firefighters is not bounded and we propose an optimal on- line algorithm which reaches the inverse of the golden ratio if at most 2 firefighters are available. Finally, we show that on infinite trees with linear growth, any firefighter sequence stronger than a non-zero periodic sequence is sufficient to contain the fire, even when revealed online.

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18064
15/03/2018

Soft-Cascade Learning with Explicit Computation Time Considerations

FBARBOSA ANDA, F.LERASLE, C.BRIAND, A.A.MEKONNEN

RAP, ROC

Manifestation avec acte : IEEE Winter Conference on Applications of Computer Vision ( WACV ) 2018 du 12 mars au 15 mars 2018, Lake Tahoe (USA), Mars 2018, 10p. , N° 18064

Lien : https://hal.archives-ouvertes.fr/hal-01726292

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Abstract

This paper presents a novel framework for learning a soft-cascade detector with explicit computation time considerations. Classically, training techniques for soft-cascade detectors select a set of weak classifiers and their respective thresholds, solely to achieve the desired detection performance without any regard to the detector response time. Nevertheless, since computation time performance is of utmost importance in many time-constrained applications , this work divulges an optimization approach that aims to minimize the mean cascade response time, given a desired detection performance, fixed beforehand. The resulting problem is NP-Hard, therefore finding an optimal threshold vector can be very time-consuming, especially when building a soft-cascade detector of long length. An efficient local search procedure is presented that deals with long-length detectors. Our evaluations on two challenging public datasets confirm that a faster cascade detector can be learned while maintaining similar detection performances .

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18029
02/03/2018

A Three-step Decomposition Method for Solving the Minimum-Fuel Geostationary Station Keeping of Satellites Equipped with Electric Propulsion

C.GAZZINO, D.ARZELIER, L.CERRI, D.LOSA, C.LOUEMBET, C.PITTET-MECHIN

MAC, ROC, CNES, Thalès Alenia Space

Rapport LAAS N°18029, Mars 2018, 14p.

Lien : https://hal.laas.fr/hal-01696455

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Abstract

In this paper, a control scheme is elaborated in order to perform the station keeping of a geostationary satellite equipped with electric propulsion while minimizing the fuel consumption. The use of electric thrusters imposes to take into account some additional non linear and operational constraints that make the overall station keeping optimal control problem difficult to solve directly. That is why the station keeping problem is decomposed in three successive control problems. The first one consists in solving a classical optimal control problem with an indirect method initialized by a direct method without enforcing the thrusters operational constraints. Starting from this non feasible solution for the genuine problem, the thrusters operating constraints are incorporated in the second problem, whose solution produces a feasible but non optimal control profile via two different ways. Finally, the third optimizes the commutation times thanks to a method borrowed to the switched systems theory. Simulation results on a realistic example validate the benefit of this particular control scheme in the reduction of the fuel consumption for the geostationary station keeping problem.

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