Odd-Cycle-Packing-treewidth: On the Maximum Independent Set problem in odd-minor-free graph classes

TL;DR

This paper introduces a new graph width parameter called Odd-Cycle-Packing-treewidth (OCP-tw), establishes its structural properties, and demonstrates its utility in efficiently solving the Maximum Independent Set problem in certain graph classes.

Contribution

It defines OCP-tw, proves a Grid Theorem analogue for it, and develops algorithms for approximating OCP-tw and solving MIS on graphs with bounded OCP-tw.

Findings

OCP-tw is monotone under odd-minor relation.

Presence of certain grid-like graphs implies large OCP-tw.

Polynomial-time algorithm for MIS on graphs with bounded OCP-tw.

Abstract

We introduce the tree-decomposition-based graph parameter Odd-Cycle-Packing-treewidth (OCP-tw) as a width parameter that asks to decompose a given graph into pieces of bounded odd cycle packing number. The parameter OCP-tw is monotone under the odd-minor-relation and we provide an analogue to the celebrated Grid Theorem of Robertson and Seymour for OCP-tw. That is, we identify two infinite families of grid-like graphs whose presence as odd-minors implies large OCP-tw and prove that their absence implies bounded OCP-tw. This structural result is constructive and implies a 2^(poly(k))poly(n)-time parameterized poly(k)-approximation algorithm for OCP-tw. Moreover, we show that the (weighted) Maximum Independent Set problem (MIS) can be solved in polynomial time on graphs of bounded OCP-tw. Finally, we lift the concept of OCP-tw to a parameter for matrices of integer programs. To this end, we show that our strategy can be applied to efficiently solve integer programs whose matrices can be "tree-decomposed" into totally delta-modular matrices with at most two non-zero entries per row.