In this paper, the focus is put on multi-core branch-and-bound algorithms for solving large-scale permutationbased optimization problems. We investigate five work stealing (WS) strategies with a new data structure called integer-vector-matrix (IVM). In these strategies, each thread has a private IVM allowing the local management of a set of subproblems enumerated using a factorial system. The WS strategies differ in the way the victim thread is selected and the granularity of stolen work units (intervals of factoradics). To assess the efficiency of the private IVM-based WS approach, the five WS strategies have been extensively experimented on the flowshop scheduling permutation problem and compared with their conventional linked-list-based counterparts. The obtained results demonstrate that the IVM-based WS outperforms the linked-list-based one in terms of CPU time, memory usage and number of performed WS operations. of a process share the same virtual memory. Therefore, communications between these threads are faster than between processes. Many programming methods (such as [1-3] and [4]) based on the use of threads have been developed. To the best of our knowledge, all parallel B&B algorithms developed in the literature are based on using one or several pool(s) that store subproblems [5]. In these conventional approaches, B&B threads cooperate by adding subproblems to or removing subproblems from this or these pool(s), usually implemented as a linked-list (LL). The parallel B&B algorithm stops when this or these pool(s) is or are empty.In this paper, we propose a new approach to manage the pools of subproblems of a B&B parallel algorithm using five different work stealing (WS) strategies. Our new B&B approach aims at reducing the CPU time used to manage the thread-private B&B pools, the memory behaviour of the algorithm, the number of performed WS operations and finally the total execution time.This new approach is based on the use of an integer-vector-matrix (IVM) data structure [6] to manage the thread-private B&B pools. In our stealing strategies, work units stolen by threads are intervals of factoradics instead of sets of nodes. The factoradic, called also factorial number system, is a mixed radix numeral system adapted to numbering permutations. Based on the IVM-data structure and the factoradic-based WS, we propose a multi-core B&B algorithm and its extension to a hybrid multi-core-GPU B&B algorithm.The IVM-based B&B is compared with the LL-based B&B approach by solving some hard flowshop scheduling problem instances using the five WS strategies. The multi-core IVM-based approach spends on average 11 times less time managing the pool of subproblems, and for four out of five WS strategies, idle workers wait at least 10 times less for new work. Moreover, our experimental results indicate that, for the IVM-based approach, there is no direct relation between the number of performed WS operations and the instance size, while the number of WS events in the listed-list approach clearly grows with the size of the...