Flashcards in Chapter 14 Deck (19)
refers to the assignment of start and completion times to particular jobs, people, or equipment.
ex: scheduling restaurant employees, airline crews and planes, sports teams, factory jobs
refers to determining the order in which jobs or tasks are processed.
ex: emergency room patients, automobile models on an assembly line, outgoing flights on runways
Scheduling applications and approaches
Scheduling applies to all aspects of the value chain, from planning and releasing orders in a factory, determining work shifts for employees, and making deliveries to customers.
- Software packages
- Web-based tools
attempts to match available personnel with the needs of the organization
1. Accurately forecasting demand and translating it into the quantity and timing of work to be done.
2. Determining the staffing required to perform the work by time period.
3. Determining the personnel available and the full- and part-time mix.
4.Matching capacity to demand requirements and developing a work schedule that maximizes service and minimizes costs.
can be viewed as a reservation for service time and capacity.
1. Determine the appointment time interval.
2. Determine the length of each workday and time off-duty.
3. Decide how to handle overbooking.
4. Develop customer appointment rules that maximize customer satisfaction.
1. Process-focused performance criteria (flow time and makespan)
2. Customer-focused due date criteria (lateness and tardiness)
3. Cost-based criteria
is the amount of time a job spent in the shop or factory.
Fi = ∑pij + ∑wij = Ci - Ri
is the time needed to process a given set of jobs.
M = C - S
is the difference between the completion time and the due date (either positive or negative).
is the amount of time by which the completion time exceeds the due date
tardiness is defined as zero if job is completed before due date
Shortest Processing Time (SPT)
SPT sequencing maximizes resource utilization and minimizes average flow time and work-in-process inventory.
Earliest Due Date (EDD)
EDD minimizes the maximum job tardiness and lateness.
Priority rules when new jobs arrive intermittently
1. First come-first served (FCFS).
2. Fewest number of operations remaining (FNO).
3. Least work remaining (LWR) – the sum of all processing times for operations not yet performed.
4. Least amount of work at the next process queue (LWNQ) – amount of work awaiting the next process in a job’s sequence.
Single-Resource Sequencing Problem
Process a set of jobs on a single processor.
- SPT sequencing finds a minimal average flow time sequence.
- FCFS rule works well when processing times are relatively equal.
- EDD rule minimizes the maximum job tardiness and lateness.
Two-Resource Sequencing Problem (Johnson's Rule)
1. List the jobs and their processing times on Resources #1 and #2.
2. Find the job with the shortest processing time (on either resource).
3. If this time corresponds to Resource #1, sequence the job first; if it corresponds to Resource #2, sequence the job last.
4. Repeat steps 2 and 3, using the next-shortest processing time and working inward from both ends of the sequence until all jobs have been scheduled.