The Non-Permutation Flow-Shop scheduling problem: A literature review

The Non-Permutation Flow-Shop scheduling problem (NPFS) is a generalization of the traditional Permutation Flow-Shop scheduling problem (PFS) that allows changes in the job order on different machines. The flexibility that NPFS provides in models for industrial applications justifies its use despite its combinatorial complexity. The literature on this problem has expanded largely in the last decade, indicating that the topic is an active research area. This review is a contribution towards the rationalization of the developments in the field, organizing them in terms of the objective functions in the different variants of the problem. A schematic presentation of both theoretical and experimental results summarizes many of the main advances in the study of NPFS. Finally, we include a bibliometric analysis, showing the most promising lines of future development.