Operations research
Remember it
Never forget transportation steps again
Never forget the transportation method order again. Can you name step one?
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Lesson notes
Find an initial solution (NWC, least cost, VAM) and test optimality with MODI
Key points
- Big / Balance check: First check total supply equals total demand, or add a dummy row or column.
- Ships / Supply-demand table: Ships reminds you to lay out Tema and Takoradi supplies against depot demands.
- Need / NWC or least cost: Need means an initial allocation by north-west corner or least cost method.
- Very / Vogel's approximation: Very stands for Vogel: allocate to the row or column with biggest penalty.
- Many / m+n−1 cells: Many reminds you to count occupied cells; fewer than m plus n minus one is degeneracy.
- Docks / MODI test: Docks means MODI: compute improvement indices; all non-negative means minimum cost reached.
Takeaway: Balance first, allocate, check m+n−1, then test with MODI.
Quick check: Supply is 500 tonnes but demand is 450 tonnes. What must you add first?
- A dummy depot column
- A dummy plant row
- An extra MODI index
Excess supply needs a dummy destination of 50 tonnes at zero cost.
balanced problemVogel's approximationMODI methoddegeneracy
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