2 research outputs found
Polyhedral Computations for the Simple Graph Partitioning Problem
The simple graph partitioning problem is to partition an edge-weighted graph into mutually disjoint subgraphs, each containing no more than b nodes, such that the sum of the weights of all edges in the subgraphs is maximal. In this paper we present a branch-and-cut algorithm for the problem that uses several classes of facet-defining inequalities as cuttingplanes. These are b-tree, clique, cycle with ear, multistar, and S, Tinequalities. Descriptions of the separation procedures that are used for these inequality classes are also given. In order to evaluate the usefulness of the inequalities and the overall performance of the branch-and-cut algorithm several computational experiments are conducted. We present some of the results of these experiments.Branch-and-cut algorithm; Facets; Graph partitioning; Multicuts; Separation procedures
Extraction et partitionnement pour la recherche de rĂ©gularitĂ©s : application Ă lâanalyse de dialogues
In the context of dialogue analysis, a corpus of dialogues can be represented as a set of arrays of annotations encoding the dialogue utterances. In order to identify the frequently used dialogue schemes, we design a two-step methodology in which recurrent patterns are first extracted and then partitioned into homogenous classes constituting the regularities. Two methods are developed to extract recurrent patterns: LPCA-DC and SABRE. The former is an adaptation of a dynamic programming algorithm whereas the latter is obtained from a formal modeling of the extraction of local alignment problem in annotations arrays.The partitioning of recurrent patterns is realised using various heuristics from the literature as well as two original formulations of the K-partitioning problem in the form of mixed integer linear programs. Throughout a polyhedral study of a polyhedron associated to these formulations, facets are characterized (in particular: 2-chorded cycle inequalities, 2-partition inequalities and general clique inequalities). These theoretical results allow the establishment of an efficient cutting plane algorithm.We developed a decision support software called VIESA which implements these different methods and allows their evaluation during two experiments realised by a psychologist. Thus, regularities corresponding to dialogical strategies that previous manual extractions failed to identify are obtained.Dans le cadre de lâaide Ă lâanalyse de dialogues, un corpus de dialogues peut ĂȘtre reprĂ©sentĂ© par un ensemble de tableaux dâannotations encodant les diffĂ©rents Ă©noncĂ©s des dialogues. Afin dâidentifier des schĂ©mas dialogiques mis en oeuvre frĂ©quemment, nous dĂ©finissons une mĂ©thodologie en deux Ă©tapes : extraction de motifs rĂ©currents, puis partitionnement de ces motifs en classes homogĂšnes constituant ces rĂ©gularitĂ©s. Deux mĂ©thodes sont dĂ©veloppĂ©es afin de rĂ©aliser lâextraction de motifs rĂ©currents : LPCADC et SABRE. La premiĂšre est une adaptation dâun algorithme de programmation dynamique tandis que la seconde est issue dâune modĂ©lisation formelle du problĂšme dâextraction dâalignements locaux dans un couple de tableaux dâannotations.Le partitionnement de motifs rĂ©currents est rĂ©alisĂ© par diverses heuristiques de la littĂ©rature ainsi que deux formulations originales du problĂšme de K-partitionnement sous la forme de programmes linĂ©aires en nombres entiers. Lors dâune Ă©tude polyĂšdrale, nous caractĂ©risons des facettes dâun polyĂšdre associĂ© Ă ces formulations (notamment les inĂ©galitĂ©s de 2-partitions, les inĂ©galitĂ©s 2-chorded cycles et les inĂ©galitĂ©s de clique gĂ©nĂ©ralisĂ©es). Ces rĂ©sultats thĂ©oriques permettent la mise en place dâun algorithme de plans coupants rĂ©solvant efficacement le problĂšme.Nous dĂ©veloppons le logiciel dâaide Ă la dĂ©cision VIESA, mettant en oeuvre ces diffĂ©rentes mĂ©thodes et permettant leur Ă©valuation au cours de deux expĂ©rimentations rĂ©alisĂ©es par un expert psychologue. Des rĂ©gularitĂ©s correspondant Ă des stratĂ©gies dialogiques que des extractions manuelles nâavaient pas permis dâobtenir sont ainsi identifiĂ©es