Test AMPL and popular solvers for free using a convenient online service.

To simplify the work of comparing and testing solvers, we have made AMPL and solver resources available “in the cloud” in collaboration with the NEOS Server project.

What is the NEOS server?

The NEOS Server is a free internet-based service for solving numerical optimization problems. Hosted by the Wisconsin Institute for Discovery at the University of Wisconsin in Madison, the NEOS Server provides access to more than 60 state-of-the-art solvers in more than a dozen optimization categories. Solvers hosted by the University of Wisconsin in Madison run on distributed high-performance machines enabled by the HTCondor software; remote solvers run on machines at Arizona State University, the University of Klagenfurt in Austria, and the University of Minho in Portugal.

AMPL users can interact with the NEOS server in either of two ways:

  • by requesting execution of both AMPL and solvers at a remote site, or

  • by using a local AMPL session to send optimization problems to remote solvers.

These services, described in more detail below, are available free of charge, using any Internet connection. They have proved valuable for testing, prototyping, teaching, and small-scale projects. Pursuant to the posted terms of use, the NEOS project makes no guarantees of performance or confidentiality.

Remote AMPL with remote solvers: The NEOS website

This facility lets you send an AMPL “job” to one of the NEOS Server’s remote computers. A job consists of an AMPL model file, plus optionally an associated data file, plus optionally a command file containing an AMPL script to be executed.

When you submit a job, the NEOS Server’s central scheduler locates an appropriate remote computer on which to run it, holding the job in a queue if necessary. When a remote computer is available, the server sends it instructions to start up a copy of the AMPL processor, and it handles the rest of the computations. Thus the remote computer automatically reads and executes the submitted files, runs the requested solver, and gathers the resulting output for return to the Server. The Server reports the output on the submission website and emails a copy to the user. AMPL’s display or printing commands can be included in the command file to produce listings of results that are sent back along with other AMPL output.

To use this facility, follow a link below to consult the page of instructions for the solver in which you are interested. Solvers currently available for AMPL modeling include the following: 

Each solver submission page provides summary solver information, links for additional information sources, and specific instructions for sending optimization problems to the solver via the NEOS Server.

Local AMPL with remote solvers: The Kestrel client

In this mode of operation, you run your own copy of AMPL on your local computer. But instead of specifying a solver installed on your computer or local network, you invoke Kestrel, a “client” program that sends your problem to a solver running on one of the NEOS Server’s remote computers. The results from the NEOS Server are eventually returned through Kestrel to AMPL, where you can view and manipulate them locally in the usual way. Thus you get all the benefits of using AMPL environment, without having to first obtain and install each solver you want to try.

The introduction below covers everything you need to know to start using Kestrel with AMPL. There is also a paper about Kestrel that describes more advanced features and other uses.

Downloading and installing the Kestrel client

To get started using this feature, you must obtain the free Kestrel program. Kestrel downloads are available from the My Downloads page of your account at the AMPL Portal, and are included in the demo bundles that are used for free trials. 

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