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Dominique de Werra

Publications associées (46)

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On two coloring problems in mixed graphs

Dominique de Werra, Bernard Ries

We are interested in coloring the vertices of a mixed graph, i.e., a graph containing edges and arcs. We consider two different coloring problems: in the first one we want adjacent vertices to have different colors and the tail of an arc to get a color str ...

2008

Polarity of chordal graphs

Dominique de Werra, Tinaz Ekim

Polar graphs are a common generalization of bipartite, cobipartite, and split graphs. They are defined by the existence of a certain partition of vertices, which is NP-complete to decide for general graphs. It has been recently proved that for cographs, th ...

2008

Polar cographs

Dominique de Werra, Tinaz Ekim

Polar graphs are a natural extension of some classes of graphs like bipartite graphs, split graphs and complements of bipartite graphs. A graph is (s, k)-polar if there exists a partition A, B of its vertex set such that A induces a complete s-partite grap ...

Elsevier2008

Construction of balanced sports schedules using partitions into subleagues

Dominique de Werra, Tinaz Ekim

Direct constructions for balanced tournaments known so far solve problems with 2n teams if 2n mod 3 not equal 1 or 2n = 2(p), p >= 3 or n is odd. Our construction uses an arbitrary partition of the league into subleagues. It solves more than half of the mi ...

2008

Bicolored matchings in some classes of graphs

Dominique de Werra, Bernard Ries

We consider the problem of finding in a graph a set

R

of edges to be colored in red so that there are maximum matchings having some prescribed numbers of red edges. For regular bipartite graphs with

n

nodes on each side, we give sufficient conditions f ...

2007

Variations of split-coloring in permutation graphs

Dominique de Werra, Tinaz Ekim

Combinatorial optimization problems related to permutations have been widely studied. Here, we consider different generalizations of the usual coloring problem in permutation graphs. A cocoloring is a partition of a permutation into increasing and decreasi ...

2006

Partitioning cographs into cliques and stable sets

Dominique de Werra, Tinaz Ekim

We consider the problem of partitioning the node set of a graph into p cliques and k stable sets, namely the (p,k)-coloring problem. Results have been obtained for general graphs \cite{hellcomp}, chordal graphs \cite{hellchordal} and cacti for the case whe ...

2005

Polar cographs

Dominique de Werra, Tinaz Ekim

Polar graphs are a natural extension of some classes of graphs like bipartite graphs, split graphs and complements of bipartite graphs. A graph is (s,k)-polar if there exists a partition A,B of its vertex set such that A induces a complete s-partite graph ...

2005

Preemptive open shop scheduling with multiprocessors: polynomial cases and applications

Dominique de Werra

This paper addresses a multiprocessor generalization of the preemptive open-shop scheduling problem. The set of processors is partitioned into two groups and the operations of the jobs may require either single processors in either group or simultaneously ...

2004

Recherche opérationnelle pour ingénieurs I

Dominique de Werra, Thomas Liebling, Jean-François Hêche

Permettant la conception et l'entretien de systèmes logistiques et techniques toujours plus complexes, la recherche opérationnelle fait aujourd'hui partie du bagage essentiel à tout ingénieur. Avec un formalisme mathématique réduit, ce livre offre une intr ...

PPUR2003

Bicolored matchings in some classes of graphs

Dominique de Werra, Bernard Ries

We consider the problem of finding in a graph a set

R

of edges to be colored in red so that there are maximum matchings having some prescribed numbers of red edges. For regular bipartite graphs with

n

nodes on each side, we give sufficient conditions f ...

2007