A Parallel Branch and Bound Algorithm for the Maximum Labelled Clique   Problem
  The maximum labelled clique problem is a variant of the maximum clique problem where edges in the graph are given labels, and we are not allowed to use more than a certain number of distinct labels in a solution. We introduce a new branch-and-bound algorithm for the problem, and explain how it may be parallelised. We evaluate an implementation on a set of benchmark instances, and show that it is consistently faster than previously published results, sometimes by four or five orders of magnitude. 
Ciaran McCreesh and Patrick Prosser
cs.DS cs.DC cs.SI