1.NEH principle

(1) the processing time of each workpiece on all machines is summed; the summed values are sorted from large to small;
(2) first select the first workpiece (the longest processing time), with the second workpiece into the first workpiece before and after the two positions, calculate makespan, small is saved;
(3) fix the sequence in the previous step, insert the next workpiece into the previous workpiece, and compare the smallest makespan and save it;
(4) Repeat the previous step to arrive at the final result.