Difference: WhiskasCatFoodProblem (47 vs. 48)

<-- Ready to Review -->

ampl: include whiskas.run;
CPLEX 10.1.0: optimal solution; objective 0.52
2 dual simplex iterations (0 in phase I)
Amount [*] :=
   BEEF  60
CHICKEN   0
    GEL  40
 MUTTON   0
   RICE   0
  WHEAT   0
;

This solution indicates that the mix of ingredients for minimising the cost of a can of Whiskas cat food is to use 60g of beef and 40g of gel. The cost of the can will be 52c.

For the Whiskas Cat Food Problem we will not perform any post-optimal analysis. However, this is the example case study for SensitivityAnalysis and ParametricAnalysis.

Validation To validate our solution for the Whiskas Cat Food Problem, we can do a quick check that our solution makes sense. First, the amounts should add up to the weight of the can (e.g., 60g + 40g = 100g). If not, there is something wrong.

Next, we can do a quick check of the constraints to ensure none of them are violated. For large models you won't always be able to check the solution by hand. However, you can use AMPL expressions to quickly calculate quantities needed for validation.

ampl: display {r in REQUIREMENTS} sum {i in INGREDIENTS} Contributes[r, i] * Amo
unt[i];
sum{i in INGREDIENTS} Contributes[r,i]*Amount[i] [*] :=
    FAT    6
  FIBRE    0.3
 ONECAN  100
PROTEIN   12
   SALT    0.3
;

ampl: display Lower, Upper;
:           Lower       Upper       :=
FAT               6   Infinity
FIBRE     -Infinity          2
ONECAN          100        100
PROTEIN           8   Infinity
SALT      -Infinity          0.4
;

The final validation is to write up a management summary for your manager and/or client and see if they think your solution is a valid one. If they identify some (or all) of the solution that is not valid, then you should discuss with them the reasons why it is invalid and start a "feedback" loop in the Operations Research methodology. | |*FORM FIELD Conclusions*|Conclusions|The solution for the Whiskas Cat Food Problem is a simple one to summarise. Here is the management summary for the Whiskas Cat Food Problem.

Important When presenting your solution you must be careful about the number of decimal places you use. You should not use a greater accuracy than your data allows.

Implementation and Ongoing Monitoring The first step towards Implementation of a solution is a good management summary. You may also want to discuss any issues that may arise from the solution you have found with Uncle Ben's (e.g., if you solution can be implemented on their production line).

Ongoing Monitoring may take the form of:

1. Updating your data files and resolving as the data changes (changing costs, nutritional requirements, etc);
2. Resolving our model for new products (e.g., 200g cans);
3. Looking for possible savings (e.g., analysing the cost of the ingredients to see if any price changes will affect the ingredient mix).|