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Service Manager. Forecasting (traffic, orders, …) Determine the Level of Service (Newsboy) Estimate Manpower Requirements Shift Scheduling (LP, IP) Assigning Shifts to Workers (Assignment, LP) Job Sequencing and Scheduling. Determine the Level of Service.
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Service Manager Forecasting (traffic, orders, …) • Determine the Level of Service (Newsboy) • Estimate Manpower Requirements • Shift Scheduling (LP, IP) • Assigning Shifts to Workers (Assignment, LP) • Job Sequencing and Scheduling
Determine the Level of Service • Choose Service Criteria (t.d. Average Waiting Time or P(wait>T) • P(wait) or P(balking) • “Newsboy Problem” • Probability Distribution of Demand • Estimate Cost Under & Over • Usually difficult => Service Level
Manpower Requirements • Experience • Statistics • Queueing Theory • QTP, Armann Ingolfsson • Simulation: • @Risk, Crystal Ball • Simul8 • ProModel
Queueing Theory • Analytical Models of Waiting Systems • Markov-assumptions, i.e. expon (both arrivals & service) <=> Poisson • Memoryless Process! • Open/Closed System (“Limited Source”) • Wait/Balk (“Limited Queue”) • Steady State: Arrivals < Capacity
Open Systems, M/M/s • M/M/1 og M/M/s TEMPLATE.XLS • Given: Arrival og cap. s*µ ,Ws=1/µ • Steady State: U = Ls/s = / s*µ < 1 • Key Results: L, Lq, W, Wq • L = Lq + Ls, W = Wq + Ws • Little: L = *W og Lq= *Wq
Optimizing Waiting Systems • Given (beside , µ): Cs og Cq • Find economical no of servers s • Difficult to estimate Cq, therefore service level • Other models, see G/G/s (approx) etc • LIMITED_Q_TEMPLATE.XLS • LIMITED_SOURCE_TEMPLATE.XLS
Simulating Waiting Systems • Simulation more realistic, “you can always simulate”! • Not limited to Markov assumptions • Sometimes expensive model building • Sometimes too great expectations • MULTISERVERSIM.XLS • Simul8, ProModel, …
Shift Scheduling • Scheduling shifts on days/weeks • See p. 148 in Rardin • Based on known manpower requirements • Ex p. 142 í W&A, WorkerScheduling.xls, Work 5 days, off 2 days • Determine how many start at time t • Min no of employees needed, LP
Assigning shifts or tasks • “Assignment”, see p 235- in W&A • Transport Model with all RHS = 1 • Assigning jobs to men/machines • Swim Teams, Exam Shedules, Fishing Vessels Landings, … See p 58 in Rardin • “Crew Scheduling”, See p 572 in Rardin • Assigning Shifts: Employees grade shifts
Job Sequencing • See p 609- in Rardin • Orders or Batches • Given: Processing Times, Due Dates • Criteria: Flow and/or Due Dates • Rules: FCFS, SPT, Slack, EDD • Complexity: n jobs to m machines, min setup time, …