1. EMIS 8373: Integer Programming
Introduction to AMPL
updated 10 January 2006

2. Starting AMPL

3. Entering the GT Railroad Problem

4. Solving the GT Railroad Problem

5. A General Transportation Modelh e s t o f r i g n D d a u m b v l j q c p x m i n X 2 O ; j D c x s u b e t o a 8 r

6. transport_model.txt set O; set D; param a {i in O}; param r {j in D};
param c {i in O, j in D};
var x {i in O, j in D} >= 0;
minimize cost: sum {i in O, j in D} c[i,j] * x[i,j];
subject to supply {i in O}: sum {j in D} x[i,j] <= a[i];
subject to demand {j in D}: sum {i in O} x[i,j] >= r[j];

7. GT_data.txt set O := IE_Junction, Centerville, Wayover_City;
set D := A_Station, Fine_Place, Goodville, Somewhere_Street;
# supply
param a :=
IE_Junction     4
Centerville     1
Wayover_City    2;
# demand
param r :=
A_Station       1
Fine_Place      1
Goodville       1
Somewhere_Street        1;

8. GT_data.txt
param c :                A_Station       Fine_Place      Goodville       Somewhere_Street :=
IE_Junction                                              
Centerville                    61                           
Wayover_City            ;      

9. Solving the Model with GT_data.txt

10. The expand Command

11. The expand Command

12. Editing the Data File

13. Edited GT_data.txt set O := IE_Junction, Centerville, Wayover_City;
set D := A_Station, Fine_Place, Goodville, Somewhere_Street;
# supply
param a :=
IE_Junction     3
Centerville     3
Wayover_City    3;
# demand
param r :=
A_Station       2
Fine_Place      2
Goodville       2
Somewhere_Street        2;

14. Resolving the Model

15. New Optimal Solution

16. Display the Results to a File

17. Using AMPL Student Edition on Windows
Download AMPL Student Edition
Download model and data file from Blackboard
transport_model.txt
GT_data.txt
Save the files in the amplcml directory created in step 1
Double click on the AMPL icon to start AMPL

19. Solving the Model

20. Solving the Model with CPLEX

21. Edit GT_data.txt with WordPad

22. Find New Solution and Save Results

23. Viewing the Results
Quit AMPL
Open results.txt with WordPad or Word