Chapter 17
Since there are three tankers and three loading docks each loading dock must be assigned to a tanker.
! EACH LOADING DOCK MUST BE ASSIGNED A TANKER;
The constraints that require each tanker to be assigned a loading dock, and each loading dock
assigned a tanker form the constraint set for the assignment problem. The assignment problem was
introduced in Chapter 6. However, unlike the assignment problem the objective function in this
problem is nonlinear. Consider, for example, the result of assigning tanker 1 to dock 2 and tanker 3
to dock 1. The distance between loading docks 1 and 2 is 100 meters. Also, tanker 1 must transfer
80 tons of goods to tanker 3. This means that 80 tons must be moved 100 meters. To capture this in
MIN = 100*60*X11*X22 + 150*60*X11*X23 + 100*80*X11*X32 +
150*80*X11*X33
+ 100*60*X12*X21 + 50*60*X12*X23 + 100*80*X12*X31 + 50*80*X12*X33
+ 150*60*X13*X21 + 50*60*X13*X22 + 150*80*X13*X31 + 50*80*X13*X32;
The solution to this model is
Global optimal solution found.
Objective value: 10000.00
Extended solver steps: 0
Total solver iterations: 38
Variable Value Reduced Cost
X11 0.000000 0.000000
X22 0.000000 0.000000
X23 0.000000 0.000000
X32 0.000000 0.000000
Thus tanker 1 should be assigned to dock 2, tanker 2 to dock 1 and tanker 3 to dock 3.
Depending on the starting point, Excel Solver will likely get stuck at a local optimum and not the
find the optimal solution that LINGO finds.
27. The objective is to minimize total production cost. To minimize total product cost minimize the
production cost at Aynor plus the production cost at Spartanburg. Minimize the production cost at
the two plants subject to the constraint that total production of kitchen chairs is equal to 40. The
model is: