I. Introduction
Flexible job shop scheduling problem (FJSP) is closer to actual production, which has received widespread attention. FJSP can be divided into total flexible job shop scheduling(TFJSP) and partially flexible job shop scheduling(PFJSP), while TFJSP means that any processes can be processed on all machines, and the processes of PFJSP can only be done on available machines. Process path flexibility makes FJSP a more complex NP-hard problem.