Extending interval branch-and-bound from two to few objectives in nonlinear multiobjective optimization

Nonlinear multiobjective optimization presents significant challenges, particularly when addressing problems with three or more objectives. Building on our previous work using Interval Branch and Bound (B&B) techniques for biobjective optimization, we extend these methods to handle the increased complexity of multiobjective scenarios. Interval B&B methods involve dividing the original problem into smaller subproblems and solving them recursively to achieve a desired level of accuracy. These methods offer the advantage of guaranteeing global optimality and providing rigorous bounds on solution quality. We introduce a refined representation of non-dominated regions using two sets of vectors: the non dominated feasible vectors found so far and its associated set of extreme vectors. To accurately define the feasible non-dominated region within each subspace, we adapt an “envelope constraint” from biobjective solvers. Additionally, we propose a novel method for computing the distance from a subspace to the dominated region, and enhance a peeling technique for contracting the subspace based on the dominated region and the envelope constraint. Our approach is evaluated on a set of benchmark problems, and our results show a significant improvement in solution quality and convergence speed compared to a basic approach. Specifically, our enhanced strategy achieves a 42% reduction in relative CPU time, with a remarkable average time reduction of 63% in problems with three objectives. The code of our solver can be found in our git repository ( https://github.com/INFPUCV/ibex-lib/tree/master/plugins/optim-mop ).