AMPL FAQS

Ø I don’t have a copy of the AMPL book. Where can I go for help?

You might share a copy of the ampl book with your team mates --- that's about $10 each. No text is required for the class. If I had required the AMPL book....

You can look at lots of examples at

http://www.ampl.com/EXAMPLES/index.html

You can get the 1st chapter of the book at

http://www.ampl.com/BOOK/contents.html

Type the two words "AMPL" and “your command” into Google. That will generate lots of examples.

Ø I don't quite understand this peice of code in your lecture:

set EDGES := (PLANTS cross DCS) union (DCS cross CUSTS);

More specifically, I can guess what it means, but I have trouble using EDGES later on in the model.

You need to define the set EDGES. It's the "within" command that's giving you problems. It limits what can be in the set EDGES, but does not say what is in the set edges. Try this:

let PLANTS := {'plant1', 'plant2'};

let PRODUCTS := {'prod1', 'prod2'};

let CUSTS := {'cust1', 'cust2'};

let DCS := {'dc'};

/* This statement defines the set of EDGES. It is what you are missing */

let EDGES := PLANTS cross DCS union DCS cross CUSTS;

let {prd in PRODUCTS, p in PLANTS} Supply[prd, p] := 5;

let {prd in PRODUCTS, c in CUSTS} Demand[prd, c] := 4;

let {(i, j) in EDGES} Cost[i,j] := 1;

let {(i,j) in EDGES} Capacity[i,j] := 100;

save this as:

Example.run

invoke ampl

model [your model file].mod;

include example.run;

solve;

display Flow;