Information about CPLEX and AMPL

CPLEX is free for students and academics

Join the IBM Academic Initiative. You can run CPLEX in standalone mode, or you can call it from C or C++ or Matlab or Python.

Background information and reading

AMPL is a mathematical programming and optimization modeling language which can be used to solve linear, integer, and nonlinear programming problems. You can input your model into AMPL in a reasonably intuitive way and it will use a solver (such as MINOS or CPLEX) for solving the problem. It is capable of solving linear, nonlinear, and integer programs.

The AMPL website contains the whole of the AMPL book.

The student version of AMPL

The AMPL website contains downloadable executables for use in Windows or in Unix/Linux systems, including Mac OSX. These executables are limited in the size of problems they can solve.

Note that if you use the command line interface with Windows and you use Word to create and edit the files, Word will add txt to the end of a filename when stored as a text file. For example, if your model is called zoff.mod and you created it and stored it using Word, the file will be called zoff.mod.txt. To read it into AMPL, you will need to use the command

ampl: model zoff.mod.txt;

More on solvers

AMPL is a modelling language. It uses other packages to actually solve optimization problems.

Here is some more information about working with AMPL.

The NEOS Server

AMPL can also be run remotely on the NEOS server. You submit your model and data files and it will give you the solution.

Examples:

Here are some more AMPL examples.
More examples, including a set formulation of a general production problem together with three data files. And yet more examples.
The CPLEX distribution of AMPL examples can be found here.
An excellent collection of nonlinear programming models. A good place to start may be the block QP models in the Cute set, for example blockqp1.mod.
My page of generators for nonconvex quadratically constrained quadratic programs contains more involved examples, with run files that solve multiple problems, that use the output from one problem in the input to another, that use random number generators, and that use if-then-else statements and loops.

Web resources and hints

The CPLEX manual is part of the software distribution. So when you download and install cplex on your computer, it creates a documentation folder. The documentation comes in both html and pdf format. It should give you some sort of introduction to modeling as well as to the syntax of CPLEX. It also includes some tutorials in the gscplex.pdf file. There is also a folder of examples included in the distribution. The documentation also includes information about installing CPLEX.
More information about working with AMPL and getting more from it.
An AMPL tutorial, originally prepared by Phil Kaminsky at Berkeley.
The CPLEX website. This uses the IIS options within CPLEX. In particular, you can use the AMPL command
option cplex_options 'iisfind 1';
Displaying the values of all variables simultaneously.

John Mitchell