Johnson's approximate method for the 3 × n job shop problem

The effectiveness of Johnson's Approximate Method (JAM) for the 3 × n job shop scheduling problems was examined on 1,500 test cases with n ranging from 6 to 50 and with the processing times Ai, Bi, Ci (for item i on machines A, B, C) being uniformly and normally distributed. JAM proved to be quite effective for the case Bi ⩽ max (Ai, Ci) and optimal for Bi, ⩽ min (Ai, Ci).