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Experimental AMPL Graphical Interfaces

17 December 1999: Three new experimental GUIs for AMPL are available free for downloading. They have a common style, but differ somewhat in details and capabilities. Tcl/Tk and Java versions are available as source code, and can be run on many popular Microsoft, Unix and Linux platforms. A Visual Basic version is available in the form of an executable including AMPL, the MINOS solver, and the interface; it requires Windows 95 or later. See the new experimental AMPL GUI page for further details including download information and screen shots.

AMPL Plus version 1.6

17 December 1999: A new version of the AMPL Plus graphical user interface for AMPL, CPLEX and MINOS is now available. Contact ILOG, Inc. for further information on purchases or upgrades.

AMPL Plus Student Edition version 1.6

17 December 1999: Beginning in early 2000, the AMPL book is to be shipped with updated software on CD. Components will include a student edition of the AMPL Plus version 1.6 graphical user interface for Microsoft Windows, restricted to 300 variables and 300 constraints plus objectives but otherwise complete except for certain advanced database access features, plus the CPLEX 6.5.3 and MINOS 5.5 solvers. For more detailed information, consult the readme file that comes with the new book software.

If you purchased an earlier copy of the AMPL book, you can arrange to download the new AMPL Plus Student Edition 1.6 software. See our book software upgrade instructions for details.

MProbe 3.0

6 October 1999: A new version of the MProbe Nonlinear Function Analyzer for AMPL models features offers numerous new plotting options, sampling inside any convex enclosure (for improved accuracy of conclusions), and identification of redundant constraints and bounds. A student/demo edition of the new version, bundled with the AMPL Student Edition software, is available for downloading.

AMPL Software Download Page

5 September 1999: We’ve collected in one place the instructions for downloading many versions of AMPL and solvers that are available at no charge. These versions are restricted to problems of limited size — in most cases, to 300 variables and 300 constraints and objectives — but are full-featured in other respects. They can be used to update the AMPL Student Edition software that comes with the AMPL book, or to set up a demonstration version for small-scale evaluation and testing.

Solvers for which downloadable versions are referenced include CPLEX, DONLP2, LOQO, lp_solve, MINOS, and WSAT(OIP).

Next-day Shipping for the AMPL Book

1 September 1999: AMPL: A Modeling Language for Mathematical Programming is now shipping within 24 hours most days when ordered via our Optimization Bookstore.

We link to Barnes & Noble or, depending on which seems to be shipping fastest. If you’re determined to get the lowest possible price, you might also want to try the listings from AddAll or BestBookBuys; try searching on the book’s ISBN, 0534378951.

Expanded Lineup of AMPL Vendors

11 August 1999: Unicom Consultants is the latest addition to the list of AMPL vendors. Unicom also sells FortMP solver software, several specialized optimization packages, and consulting services in database design, web publishing, and optimization.

23 April 1999: Dash Optimization, Inc. has been added to the list of AMPL vendors. Dash also sells XPRESS-MP solver software, as well as consulting, training and customization services.

25 March 1999: Optimal Solution Technologies, Inc. has joined our lineup of AMPL vendors. OST also sells IBM OSL solver software and service, and offers consulting services for data management, modeling and analysis, and supply chain optimization.


4 August 1998: A simplified interface to the AMPL Student Edition lets you experiment with AMPL on test problems up to 300 variables and 300 constraints + objectives. Request any example from the AMPL book, or use your own model and data files. Specify AMPL commands for setting options, solving, and displaying results; choose among 8 solvers for linear, nonlinear, and integer programming and complementarity problems. Then push the “Send” button to solve on our computer. Your most recent input and cumulative results are returned on one web page, so that it’s easy to make changes and solve again.

For other AMPL remote execution alternatives, see our description of AMPL Remote Access via the NEOS Server.

Enhanced Solver Interface Features

4 August 1998: New status features automatically start simplex solvers from the most recent optimal basis, examine or modify basis status, and test for infeasibility, unboundedness, and other solver results. New suffix features expand the range of specialized information that can be exchanged with solvers. For example, CPLEX uses user-defined suffixes to specify individual priorities for integer variables, and solver-defined suffixes to provide diagnostic information for infeasible problems and to report sensitivity ranges.

Complementarity Problems

3 April 1998: A new constraint operator, complements, permits linear and nonlinear complementarity problems to be expressed directly and naturally as AMPL constraints. Both standard and mixed complementarity conditions are supported. The first solver to take advantage of these new forms is Dirkse and Ferris’s PATH; users can download the the AMPL/PATH interface routines from netlib.

MProbe 2.0

28 February 1998: A new version of the MProbe Nonlinear Function Analyzer for AMPL models features a faster 32-bit implementation, recognition of quadratic forms, and tools for assessing constraint region convexity, constraint “effectiveness” and likelihood of a global optimum. A student/demo version bundled with the AMPL Student Edition remains available for downloading.

AMPL Remote Access

1 February 1998: To simplify the work of comparing and testing solvers, we have undertaken a project to make AMPL and solver resources available over the Internet, in collaboration with the NEOS Server project of the Argonne/Northwestern Optimization Technology Center. AMPL users can interact with the NEOS server by requesting runs of both AMPL and solvers at a remote site, or by using a local AMPL session to send optimization problems to remote solvers. Five solvers — DONLP2, LANCELOT, LOQO, MINOS, and SNOPT — are initially available.

AMPL in Action: Toxic Waste Disposal

15 November 1997: In this addition to the AMPL in Action case studies section, a pharmaceutical and chemicals company seeks to improve its scheduling of a special toxic waste furnace. An AMPL mixed-integer program determines a solution that increases throughput by 20% while more evenly distributing filter load and reducing slag burnoff.

AMPL in Action: “Balanced Assignment”

16 October 1997: A company divides its employees at meetings and training sessions into groups “as diverse as possible” with respect to several characteristics. The resulting problem differs in key ways from the textbook “assignment problem” and other familiar applications of optimization. AMPL’s power and flexibility are advantageous in trying out many alternative models in for quickly modifying models to accommodate new requirements.

NEOS Server for LOQO Supports AMPL Input

14 October 1997: AMPL models, data and command files for linear and quadratic programs can now be submitted to the NEOS Server for solution by LOQO. Submissions can be made (and results returned) either through a web page or by e-mail. AMPL support is planned for a number of other solvers currently supported by NEOS.

AMPL Interface for XPRESS-MP

12 September 1997: The XPRESS-MP solvers for linear programming (simplex or interior) and integer programming are now available with an AMPL interface. Contact Dash Associates for further information.

Enhanced LOQO 3.07 with Built-In AMPL Interface

16 August 1997: The newly released version 3.07 of Vanderbei’s LOQO solver finds locally optimal points for general (smooth) nonlinear functions (as well as global optimums for the usual linear and convex cases). You can download demo executables with a built-in AMPL interface for most popular Unix workstations and for PCs running Linux. Just install the executable file loqo in your search path and set option solver loqo to access the new version from AMPL when you issue a solve command. Since LOQO’s interior-point algorithm requires Hessian (2nd derivative) information, AMPL is the currently the only modeling language that supports it for general nonlinear optimization.

Shared Libraries for User-Defined Functions

21 July 1997: AMPL now provides a more convenient way to make your own functions available to models and solvers, through the use of shared libraries (also known as dynamic-link libraries, or DLLs). A new ampl/solvers/funclink directory in netlib provides an introduction, together with system-dependent examples and makefiles.

AMPL in Action

3 June 1997: This new section presents five summaries of practical AMPL applications:

All are reprinted from Compass News, the newsletter of Compass Modeling Solutions, Inc.

Expanded Support for Nonlinear Solvers

25 April 1997: AMPL’s public routines for linking to nonlinear solvers have been extended in two significant respects:

  • Automatic recognition of partial separability. A nonlinear function can be recognized as a sum of terms that each depend on only a few variables (possibly after a linear change of variables).
  • Computation of Hessians. Elements of the matrix of 2nd derivatives can be computed in a range of forms. Partial separability can be exploited to speed the computations.

These routines, together with new utilities to simplify linking with solvers of all kinds, are documented in a revised version of “Hooking Your Solver to AMPL” — now available in PDF, postscript, and hypertext form.


25 April 1997: AMPL has become the first modeling language to offer a full-featured link to the highly-regarded nonlinear solver LANCELOT. The AMPL interface automatically provides LANCELOT with the partially separable structure of nonlinear objectives and constraints, as well as Hessian information if requested.

LANCELOT is one of several solvers that you can now download at minimal cost for use with AMPL. For further information, see our updated listing of Solvers that Work with AMPL.

1997 Meetings and Tutorials

29 January 1997: Our list of conferences and tutorials of interest to optimization users has been updated and extended for 1997 (and on into 1998). Details of conference presentations on AMPL features and applications will be added as they become known.

New AMPL Student Edition Software for Windows

22 December 1996: Beginning late 1996, the AMPL book is being shipped with completely updated software. Components include a student edition of the AMPL Plus graphical user interface for Microsoft Windows, and Windows versions of standard (command-line) AMPL, MINOS 5.5, and CPLEX 4.0.

MProbe: A Nonlinear Function Analyzer for AMPL Models

22 December 1996: We have begun a section on optimization problem analysis tools that work with AMPL. The first entry is MProbe, which provides information on the convexity or concavity (or more generally, the shape) of nonlinear objective and constraint functions. This information is often useful in choosing a solver or solution strategy.

Proposed New AMPL Features

1 November 1996: This new section of the AMPL Web site will present descriptions of new features planned for inclusion in future versions of AMPL. Our first installment includes prospective AMPL extensions for stochastic programming, constraint logic programming, and a more general & powerful solver interface.

AMPL Training Seminar

1 November 1996: A session for beginning to intermediate AMPL users has been scheduled for January 20-21, 1996 in Reno, Nevada.

Software for Optimization: A Buyer’s Guide

14 October 1996: Part 2 of this article by AMPL co-developer Robert Fourer, reprinted from the Fall 1996 issue of the INFORMS Computer Science Technical Section Newsletter,has been added.

AMPL at the INFORMS Atlanta Meeting

29 September 1996: Uses of AMPL are described in a tutorial and three invited talks at this fall’s INFORMS meeting, November 3-6. The AMPL meetings page provides details, including links to abstracts.

Books on Optimization

15 August 1996: A variety of titles, most of them recommended in the Linear Programming FAQ. Most are available (on special order) from Books; simply click any title or titles to order.

Testing the Solver Return Message

13 August 1996: A new built-in symbolic parameter can be tested, using the AMPL string functions, to distinguish optimality, infeasibility, and other conditions at the most recent solver run. This feature is particularly useful in AMPL scripts that loop over one or more solve commands.

Software for Optimization: A Buyer’s Guide

6 June 1996: Part 1 of an article by AMPL co-developer Robert Fourer, reprinted from the Spring 1996 issue of the INFORMS Computer Science Technical Section Newsletter.

New Writeups for String-Handling and Other Features

24 April 1996: Descriptions of new functions, operators and conventions that help you work with set members and other character-string data in AMPL. Topics include: string functions and operators, string expressions in AMPL commands, number-to-string conversions, string-to-number conversions, character-code conversions, and display formats for strings. Examples include automatic generation of sets like {"WEEK1","WEEK2","WEEK3"} and of filename sequences like diet1.out, diet2.out, diet3.out . . .

Other newly documented features include read for importing unformatted data; delete, purge and redeclare for removing or redefining declarations of model components; and xref for listing all components dependent on a given component.

Downloadable Student Editions for Unix

14 March 1996: Links to updated versions of the AMPL Student Edition for popular Unix workstations from Hewlett-Packard, IBM, Silicon Graphics and Sun, and for LINUX running on PCs. (Solvers still must be supplied independently, for now.)

The latest versions of the DOS Student Edition (which accompanies the AMPL book) also remain available for downloading.

Meetings page

5 March 1996: A listing of conferences, symposia and meetings having a substantial focus on aspects of large-scale optimization. Presentations and tutorials of special relevance to AMPL are highlighted.

Advanced AMPL Tutorial

1 March 1996: in conjunction with the spring meeting of INFORMS, Sunday, May 5, 7:00-10:00 pm, Georgetown East Room, Washington Hilton Hotel: Topics to be covered include new features (looping and if-then-else statements, implementing iterative schemes), application development (single-stepping, expanding constraints, system integration), upcoming enhancements, and more.

Optimization on the Web

17 February 1996: Expanded listings of on-line information sources.

New feature writeups in hypertext

6 February 1996: Descriptions of features added after the AMPL book’s publication have been converted to html format.

Guide to exercises

25 January 1996: Instructors may request a guide to the AMPL book’s end-of-chapter exercises.


15 January 1996: Forthcoming conferences relevant to large-scale optimization are listed, with details of AMPL-related talks and sessions.


10 January 1996: CONOPT, for nonlinear programming problems, joins the list of solvers available for use with AMPL.