The Communication Burden of Single Transferable Vote, in Practice

We study single-winner STV from the point of view of communication. First, we assume that voters give, in a single shot, their top-k alternatives; we define a version of STV that works for such votes, and we evaluate empirically the extent to which it approximates the standard STV rule. Second, we evaluate empirically the communication cost of the protocol for STV defined by Conitzer and Sandholm (2005) and some of its improvements

Single Transferable Vote: Incomplete Knowledge and Communication Issues

International audienceSingle Transferable Vote (STV) is used in large political elections around the world. It is easy to understand and has desirable normative properties such as clone-proofness. However, voters need to report full rankings, which can make it less practical than plurality voting. We study ways to minimize the amount of communication required to use single-winner STV. In the first part of the paper, voters are assumed to report their top-k alternatives in a single shot. We empirically evaluate the extent to which STV with truncated ballots approximates STV with full information. We also study the computational complexity of the possible winner problem for top-k ballots. For $k=1$, it can be solved in polynomial time, but is NP-complete when $k\geq 2$. In the second part, we consider interactive communication protocols for STV. Building on a protocol proposed by Conitzer and Sandholm (2005), we show how we can reduce the amount of communication required in practice. We then study empirically the average communication complexity of these protocols, based on randomly generated profiles, and on real-world election data. Our conclusion is that STV needs, in practice, much less information than in the worst case

Variability in Responses to Phoma medicaginis Infection in a Tunisian Collection of Three Annual Medicago Species

Spring black stem and leaf spot, caused by Phoma medicaginis, is an issue in annual Medicago species. Therefore, in this study, we analyzed the response to P. medicaginis infection in a collection of 46 lines of three annual Medicago species (M. truncatula, M. ciliaris, and M. polymorpha) showing different geographic distribution in Tunisia. The reaction in the host to the disease is explained by the effects based on plant species, lines nested within species, treatment, the interaction of species × treatment, and the interaction of lines nested within species × treatment. Medicago ciliaris was the least affected for aerial growth under infection. Furthermore, the largest variation within species was found for M. truncatula under both conditions. Principal component analysis and hierarchical classification showed that M. ciliaris lines formed a separate group under control treatment and P. medicaginis infection and they are the most vigorous in growth. These results indicate that M. ciliaris is the least susceptible in response to P. medicaginis infection among the three Medicago species investigated here, which can be used as a good candidate in crop rotation to reduce disease pressure in the field and as a source of P. medicaginis resistance for the improvement of forage legumes

Optimisation multi-objectifs des problèmes de transport à la demande : modélisation et résolution

Cette thèse s’intéresse à trouver des solutions informatiques à certains problèmes de l’optimisation combinatoire, à savoir les problèmes de tournées de véhicules. Elle aborde les problèmes de Transport A la Demande (TAD). L’objectif principal visé dans cette thèse fait appel à certaines approches exactes et certaines approches méta-heuristiques pour résoudre des problèmes d’optimisation multi-objective de Transport A la Demande avec plusieurs véhicules. En effet, nos principaux objectifs de recherche consistent à : -I) Résoudre un problème multi-objectif de Transport A La Demande multi-véhicules basé sur la qualité de service ; - II) Résoudre un autre problème de Transport A la Demande multi-objectifs multi-véhicules. Ce problème traite un cas spécifique et qui consiste à l’application de ce problème aux domaines de l’Hospitalisation A Domicile (HAD). Nous avons appliqué des algorithmes exacts de "Branch and Bound" et des méthodes méta-heuristiques telles que l’algorithme évolutionnaire "Algorithme Génétique" et l’algorithme de "Colonie de Fourmis" pour apporter des solutions efficaces à ces différents problèmes. Un ensemble de résultats numériques est présenté pour chacune de ces méthodes pour montrer leurs capacités de produire des solutions de haute qualité en temps de calcul raisonnables.This thesis focuses on finding computer science solutions for some combinatorial optimization problems, namely Vehicle Routing Problems (VRP). The thesis addresses the Dial A Ride Problems (DARP). Its main objective is to use some exact and meta-heuristics approaches to solve multi-objective optimization of Dial A Ride Problem with multi-vehicles. Hence, our main research aims are : - I)Solve a multi-objective Dial A Ride Problem with multi-vehicles based on quality of service, this problem treats a general case ; - II) Solve another multi-objective Dial A Ride Problem with multi-vehicles, this problem deals with a specific case which is an application of the Dial A Ride Problem in Home Health Care (HHC). We have also applied exact algorithms "Branch and Bound" and meta-heuristic algorithms such as evolutionary algorithms "Genetic Algorithm" and "Ant Colony" algorithm to provide effective solutions to these different problems. A set of numerical results are presented for each of these methods. Our results show that they produce high quality solutions in a reasonable execution time for all the treated problems

Détermination du gagnant à partir des règles de vote communes à l'aide des bulletins tronqués

Classical voting rules assume that voters’ ballots are complete preference orders over candidates. However, when the number of candidates is large enough, it is too costly to ask the voters to rank all candidates. There is therefore a trade-off between the efficiency of an aggregation method and the communication burden it places on voters.In this thesis, we address this problem by suggesting to ask voters to report only their k preferred candidates (where k may vary depending on the voters and/or during the process). The obtained ballots are then said to be k-truncated. We study the amount of information needed to determine the outcome of the election (exact or approximate) from truncated ballots with respect to different voting rules and we propose and analyze different methods allowing a compromise between the accuracy of the result and the amount of communication required; some require only one round of communication, while others are interactive.Les règles de vote classiques supposent que les bulletins de vote des électeurs sont des ordres de préférence complets sur les candidats. Cependant, lorsque le nombre de candidats est suffisamment élevé, il est trop coûteux de demander aux électeurs de classer tous les candidats. Il y a donc un compromis à faire entre l’efficacité d’une méthode d’agrégation des préférences et la charge de communication qu’elle fait peser sur les électeurs.Dans cette thèse, nous abordons ce problème en suggérant de demander aux électeurs de ne classer que leurs k candidats préférés (où k peut varier selon les électeurs et/ou au cours du processus). On dit que de tels votes sont k- tronqués. Nous étudions la quantité d’information nécessaire pour déterminer le résultat de l’élection (de manière exacte ou approchée) à partir de bulletins tronqués selon différentes règles de vote et nous proposons et analysons différentes méthodes permettant un compromis entre précision du résultat et quantité de communication requise ; certaines ne requièrent qu’une seule phase de communication, alors que d’autres sont dynamiques

An Exact Method To Solve The Multi-Vehicle Static Demand Responsive Transport Problem Based on Service Quality with Hard Time Windows: the case of One-to-One

International audienceWith development the technologies in the transportation systems, the distributed applications are more and more used. Because these systems needs to have Service Quality (SQ) expectations (delay, not comfortable transportation , etc.),a set of SQ oriented system aimed at aiding passengers to be more satisfied in their daily transport. Traditionally, SQ is measured by its inverse that is to say in terms of inconvenience, today it's became more and more important mainly in transportation system.If we look now at the DRT we found that it can have a middle SQ compared with other mode of transportation according to Raje et al (2003), when they defined the DRT as "services provide transport 'on demand' from passengers using fleets of vehicles scheduled to pick up and drop off people in accordance with their needs. DRT is an intermediate form of transport, somewhere between bus and taxi which covers a wide range of transport services ranging from less formal community transport through to area-wide service networks ". Selecting the best routing with the best cost according to the application requirements and DRT contexts is a challenge if we want to provide enough SQ to the customer. For that we have the idea to make a new mathematical modeling for the Static DRTP totally based on SQ.Our modeling is different from those existing in literature in the way of integration of SQ as a penalty function in the objective function. If the customer reached late to his destination there is a penalty percentage will be added to the cost which must be minimized. So we have here a new variant of the SDRTP based on SQ with hard time windows called SDRTPSQHTW. Second we are tried to solve this new variant of SDRTP with multi-vehicle in the case of One- to-One transportation type uses an exact method the Branch and Bound. The Multi-Vehicle Demand Responsive Transport Problem Based on Service Quality in the case of One-to-One (MVSDRTPBSQHTW1-t-1) under study presented this characteristic: each customer have his own origin and own destination.The aim of this paper is to find the best routing scheduled of all receipt requests with the respecting of hard Time Windows of each customer. The novelty of our paper is presented in the new manner of B&B algorithm application. However, we will trying to take the general architecture of Branch & Bound algorithm and using valuation rules in a different way which can adapted for such problem to find an optimal solution. The main idea is to applicants B&B in each vehicle such as we have a mono-vehicle problem but we are already testing all existing possible case to affect nodes to vehicles. It is very difficult to found an optimal solution to this problem since it is a NP hard mostly with using an exact methods ,but finally, we are succeed to adapt B&B algorithm and found very interesting results.</p

An Exact Method To Solve The Multi-Vehicle Static Demand Responsive Transport Problem Based on Service Quality with Hard Time Windows: the case of One-to-One

International audienceWith development the technologies in the transportation systems, the distributed applications are more and more used. Because these systems needs to have Service Quality (SQ) expectations (delay, not comfortable transportation , etc.),a set of SQ oriented system aimed at aiding passengers to be more satisfied in their daily transport. Traditionally, SQ is measured by its inverse that is to say in terms of inconvenience, today it's became more and more important mainly in transportation system.If we look now at the DRT we found that it can have a middle SQ compared with other mode of transportation according to Raje et al (2003), when they defined the DRT as "services provide transport 'on demand' from passengers using fleets of vehicles scheduled to pick up and drop off people in accordance with their needs. DRT is an intermediate form of transport, somewhere between bus and taxi which covers a wide range of transport services ranging from less formal community transport through to area-wide service networks ". Selecting the best routing with the best cost according to the application requirements and DRT contexts is a challenge if we want to provide enough SQ to the customer. For that we have the idea to make a new mathematical modeling for the Static DRTP totally based on SQ.Our modeling is different from those existing in literature in the way of integration of SQ as a penalty function in the objective function. If the customer reached late to his destination there is a penalty percentage will be added to the cost which must be minimized. So we have here a new variant of the SDRTP based on SQ with hard time windows called SDRTPSQHTW. Second we are tried to solve this new variant of SDRTP with multi-vehicle in the case of One- to-One transportation type uses an exact method the Branch and Bound. The Multi-Vehicle Demand Responsive Transport Problem Based on Service Quality in the case of One-to-One (MVSDRTPBSQHTW1-t-1) under study presented this characteristic: each customer have his own origin and own destination.The aim of this paper is to find the best routing scheduled of all receipt requests with the respecting of hard Time Windows of each customer. The novelty of our paper is presented in the new manner of B&B algorithm application. However, we will trying to take the general architecture of Branch & Bound algorithm and using valuation rules in a different way which can adapted for such problem to find an optimal solution. The main idea is to applicants B&B in each vehicle such as we have a mono-vehicle problem but we are already testing all existing possible case to affect nodes to vehicles. It is very difficult to found an optimal solution to this problem since it is a NP hard mostly with using an exact methods ,but finally, we are succeed to adapt B&B algorithm and found very interesting results.</p