Given a graph G=(V,E) and a "cost function" f: 2^{V} -> R (provided by an oracle), the problem [PCliqW] consists in finding a partition into cliques of V(G) of minimum cost. Here, the cost of a partition is the sum of the costs of the cliques in the partition. We provide a polynomial time dynamic program for the case where G is an interval graph and f belongs to a subclass of submodular set functions, which we call "value-polymatroidal". This provides a common solution for various generalizations of the coloring problem in co-interval graphs such as max-coloring, "Greene-Kleitman's dual", probabilist coloring and chromatic entropy. In the last two cases, this is the first polytime algorithm for co-interval graphs. In contrast, NP-hardness of related problems is discussed. We also describe an ILP formulation for [PCliqW] which gives a common polyhedral framework to express min-max relations such as \bchrom=\alpha for perfect graphs and the polymatroid intersection theorem. This approach allows to provide a min-max formula for [PCliqW] if G is the line-graph of a bipartite graph and f is submodular. However, this approach fails to provide a min-max relation for [PCliqW] if G is an interval graph and f is value-polymatroidal.
Bibtex entry:
@techreport{egres-06-14,
AUTHOR | = | {Gijswijt, Dion and Jost, Vincent and Queyranne, Maurice}, |
TITLE | = | {Clique partitioning of interval graphs with submodular costs on the cliques}, |
NOTE | = | {{\tt www.cs.elte.hu/egres}}, |
INSTITUTION | = | {Egerv{\'a}ry Research Group, Budapest}, |
YEAR | = | {2006}, |
NUMBER | = | {TR-2006-14} |