A note on the 2-circulant inequalities for the max-cut problem

The max-cut problem is a much-studied NP-hard combinatorial optimisation problem. Poljak and Turzik found some facet-defining inequalities for this problem, which we call 2-circulant inequalities. Two polynomial-time separation algorithms have been found for these inequalities, but one is very slow and the other is very complicated. We present a third algorithm, which is as fast as the faster of the existing two, but much simpler.