An Efficient Hybrid P2P Approach for Non-redundant Tree Exploration in B&B Algorithms

The branch and bound (B&B) algorithm is one of the most used methods to solve in an exact way combinatorial optimization problems. In a previous article, we proposed a new approach of the parallel B&B algorithm for distributed systems using the farmer-worker paradigm. However, the new farmer-worker approach has a disadvantage: some nodes of the B&B tree can be explored by several B&B processes. To prevent this redundant work and speed up, we propose a new P2P approach inspired from the strategies of existing P2P systems like Napster and JXTA. Validation is performed by experimenting the two approaches on mono-objective flow-shop problem instances using 500 processors belonging to the French national grid, Grid´5000. The obtained results prove the efficiency of the proposed P2P approach. Indeed, the execution time obtained with the P2P version, even if more communicative, is better than the farmer-worker´s one.