PSU CS410/510SS: Search and Scheduling
Lecture 6
Case Study: The Aircraft Assembly Problem At CIRL

Administrative

• Homework 3: look at it now
• Projects: CIRL-AA, job shop
• Reading for next week (online)

Lecture 6

• History
  • Barry Fox (McDonnell-Douglas) publishes scheduling ``challenge'' benchmark
  • Various results from OR community
  • CIRL takes up the challenge: ``MD4''
    • Priority Scheduling (Crawford, Ginsberg)
    • Doubleback (Crawford)
    • Noise (Parkes, Massey, Clements)
• Problem characteristics
  • 575 tasks: uneven resource use
  • 17 resources: 13 "zone" and 4 "labor"
  • Precedences
• Review: Priority Scheduling w. LDS
  • left-to-right precedence scheduling
  • LDS
  • left-to-right bin packing
  • aside: Cole's pruning rule for bin packing
  • priority pruning rule (removing symmetries): proof
• ``Doubleback'' Optimization
  • Review: local search
  • An odd fact about bin packing
  • ``right-shifting'' and ``left-shifting'' schedules
  • Proof: doubleback does optimize
  • The role of ``shifts'' in MD4
  • Initial schedules
    • PERT
    • From LDS
    • Random
• Injection of noise in DBO
  • Need local move which
    • preserves legal schedule
    • ignores heuristic
  • Solution: grab arbitrary task on prec. frontier
  • Didn't work!
  • Clements: use tiny noise (because of ``shift noise''!)
  • What didn't work: simulated annealing