Ted%20Gifford - PowerPoint PPT Presentation
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Ted%20Gifford
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Ted Gifford – PowerPoint PPT presentation
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Title: Ted%20Gifford
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Facility Location Problems At Schneider Logistics
Ted Gifford Director Research Group Schneider
National Inc
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General Background
- Subsidiary of Schneider National
- Largest truckload carrier in North America, 2001
Revenue 2.4 B, 14,000 tractors/drivers,
42,000 trailers - SLI operates in 38 countries, employs 1,200
associates - Freight Management Services
- Global, Multi-Modal Transportation
- - Manage 2.5 B purchased transportation
- Engineering Services
- Network and Route Design
- Facility Location
- Supply Chain Engineering
- Payment Services Bid Management
- Pay 7.5 billion third party invoices
- Combined Value Auctions
3
Facility Location Design at SLI
- 12-15 distinct problems / year
- 8 10 engineers participate, 30 engineers total
- Problem size Average Max
- Mfg facilities 2-10 20
- DC sites 15-30 50
- Customers 200-300 500
- Products 5-10 25
- Major Industries/Clients
- Consumer Products KC (US Europe)
- Manufacturing Otis Elevator (US Europe)
- Automotive - Ford (US Europe) GM
- Paper products Polyone
- Home Delivery (food) Schwans
4
Problem Types
5
Operational Issues
- Most problems are one-off -- A specific client
request which often has unique complications or
side constraints. - Time budget constraints often argue against
sophistication or pursuit of a mathematically
elegant solution. - Limited availability or poor quality of data is
often the main challenge and greatest consumer of
effort. - Realistic cost models are often either complex or
ill-defined. Estimates of actual costs are
highly variable. - Service requirements are often ambiguous.
Cost/service tradeoffs are unclearly specified. - Forecasts of expected demand exhibit considerable
uncertainty.
6
Current Process
- Access Database / Excel with VB Add-ins
- Basic user interface
- Navigation per problem taxonomy
- Data import maintenance
- AMPL w/ CPLEX
- MIP models
- Set Covering
- P-center
- Fixed Charge
- P-median
- Special algorithms
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Problem Taxonomy - 1
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Problem Taxonomy - 2
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Use of off-the-shelf software
- Some experience with CAPS Logic Tools, SLIM 2000,
I2 Strategist - Common difficulties
- Underlying model and MIP Formulation not visible
to user - Limited flexibility rigid parameter options
- Often necessary to trick the system for some
simple problems - Poor performance for problem structures not
anticipated by the model - Example - CAPS several hours
- Excel add-in 15 seconds
- High cost per use not general enough to handle
all problem types
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Factors which tend to complicate problems
- Ill-defined criteria
- Inconsistent or missing data
- Large number of candidate facilities
- Single sourcing requirements
- Disjunctive constraints
- Reverse logistics container flow back
- Echelon skipping
- Minimum flow constraints
- Piecewise linear (or worse) cost functions
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Current Development Activities
- Monte Carlo Simulation Risk Analysis
- Probability Distributions for Cost Demand
- Constraint Programming
- ILOG Solver / Dispatcher /OPL
- Local Search Heuristics
- Constraint Propagation / Domain Reduction
- Index variables over enumerated sets
- Special Purpose Algorithms for Global Constraints
- Conversion of AMPL to OPL
- Convert Excel Solver routines
- Utilize global set constraints
- Hybrid optimization Cooperative Solvers
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