This video is about Job Sequencing Problem , processing N Jobs on 2 machines. by the help of JOHNSON'S ALGORITHM.

JOHNSON'S RULE Steps:

: Let there be ‘n’ jobs each of which is to be processed through two machines say A & B, in the order AB. That is each job will go to machine A first and then to B in other words passing off is not allowed.

All ‘n’ jobs are to be processed on A without any idle time. On the other hand the machine B is subject to its remaining idle at various stages.

Let A1 A2………….An & B1 B2……..Bn be the expected processing time of n jobs on these two machines.

Step 1. Select the smallest processing time occurring in list Ai or Bi, if there is a tie select either of the smallest processing time.

Step 2. If the smallest time is on machine A, then place it at first place if it is for the B machine place the corresponding job at last. Cross off that job.

Step 3. if there is a tie for minimum time on both the machines then select machine A first & machine B last and if there is tie for minimum on machine A (same machine) then select any one of these jobs first and if there is tie for minimum on machine B among and select any of these job in the last.

Step 4. Repeat step 2 & 3 to the reduced set of processing times obtained by deleting the processing time for both the machines corresponding to the jobs already assigned.

Step 5. Continue the process placing the job next to the last and so on till all jobs have been placed and it is called optimum sequence.

Step 6. after finding the optimum sequence we can find the followings Total elapsed time = Total time between starting the first job of the optimum sequence on machine A and completing the last job on machine B. Idle time in machine A = Time when the last job in the optimum sequence is completed on Machine B – Time when the last job in the optimum sequence is completed on Machine A.