What’s New

at AMPL Optimization

“Logic” and Constraint Programming Extensions

22 October 2012: The AMPL language has been extended in a variety of ways to take better advantage of constraint programming and mixed-integer programming solvers that deal directly with "logic" in constraints of various kinds. Among these extensions are basic logical operators (and, or, not, exists, forall), conditional operators (if ... then ..., ==>), counting operators (count, atleast, atmost), and operators that facilitate so-called global constraints (alldiff, numberof).

Many of the extended operators are recognized by a new AMPL driver for the ILOG Concert Technology C++ interface to the IBM ILOG CP constraint programming optimizer and also the IBM CPLEX mixed-integer programming optimizer. This driver is available to all registered CPLEX for AMPL users including academic and trial license users.

See our new logic extensions page for a syntax and usage summary of all of the extended operators recognized by the new ilogcp driver.

Free Extended Function Library

22 October 2012: A new, free
function library extends AMPL with over 300 functions chosen from the GNU Scientific Library. Included are scientific, statistical, and utility functions of many kinds, and a variety of random number generators.

Once installed and declared, these functions may be applied to any arguments anywhere in an AMPL model or script. When applied to variables in objectives or constraints, they are sent to solvers, which automatically gain access to them. Thus solvers that rely on function evaluations can optimize over expressions that use this library.

Xpress for AMPL Now Available

15 October 2012: FICO
Xpress version 23 for linear, mixed integer, and quadratic programming is now available for purchase with an AMPL interface, directly from AMPL Optimization. A complete, udpated Xpress option listing details settings for access to all of the Xpress solver features. With this addition, we now offer a choice among all of the best MIP optimizers; free trials are available for benchmarking.

AMPL Book Chapters Now Free Online

28 August 2012: We are pleased to announce that chapters of "AMPL: A Modeling Language for Mathematical Programming" are now
freely available for download. This offering became possible through a recent agreement with the book's publisher, who will continue to make hardbound books available for purchase.

Victor Zverovich Joins AMPL Optimization

1 June 2012: AMPL Optimization is pleased to welcome Victor Zverovich as the newest member of the AMPL team. Victor's skills will play a key role in the development of the next generation of AMPL products.

Victor is a specialist in mathematical optimization. In 2011 he completed his PhD in Mathematics at Brunel University, UK. His main research interests are stochastic programming and algebraic modeling languages. During and after his PhD Victor worked at OptiRisk Systems on a stochastic programming solver, stochastic extensions to AMPL and an integrated development environment for those extensions. Victor has a first class honors degree in Mathematics from Belarusian State University and many years of software development experience.

Gurobi 5.0 for AMPL Now Available

15 May 2012:
Gurobi version 5.0 for linear, mixed integer, and quadratic programming is now available for purchase with an AMPL interface, both directly through us and from Gurobi Optimization. This version adds support for quadratic constraints and a variety of performance enhancements. Accounts that are up-to-date on Gurobi for AMPL maintenance and support service can download this major update immediately; other should contact licensing@ampl.com for information.

CPLEX 12.4 for AMPL Now Available

15 May 2012: IBM ILOG CPLEX version 12.4 for linear, mixed integer, and quadratic programming is now available for purchase with an AMPL interface, directly from AMPL Optimization. Accounts that are up-to-date on CPLEX for AMPL maintenance and support service can download this significant update immediately; other should contact licensing@ampl.com for information.

CPLEX 12.3 for AMPL Now Available

12 June 2011: IBM ILOG
CPLEX version 12.3 for linear, mixed integer, and quadratic programming is now available for purchase with an AMPL interface, directly from AMPL Optimization. Those who have purchased earlier versions from us can also arrange to download this update; contact licensing@ampl.com if you need to set up a download account.

Gurobi 4.5 for AMPL Now Available

15 April 2011:
Gurobi version 4.5 for linear, mixed integer, and quadratic programming is now available for purchase with an AMPL interface, both directly through us and from Gurobi Optimization. Those who have purchased earlier versions from us can also arrange to download this update; contact licensing@ampl.com if you need to set up a download account.

KNITRO 7.0 for AMPL Now Available

13 October 2010:
KNITRO version 7.0 for nonlinear optimization in continuous and integer variables is now available for purchase with an AMPL interface, both directly through us and from Ziena Optimization. Those who have purchased earlier versions from us can also arrange to download this update; contact licensing@ampl.com if you need to set up a download account.

Full-Featured MIP Solvers Available Free for Academic Use

20 September 2010: The AMPL-enabled versions of two popular mixed-integer optimizers are now available free for teaching and research at degree-granting academic institutions. These are full-featured versions that impose no arbitrary limits on problem size.

Gurobi may be included as a no-cost item on any academic license order. Those who already have AMPL academic licenses can contact us to arrange to add Gurobi, or can download solver software and academic licenses free of charge from the Gurobi website; see our Gurobi download instructions for details.

CPLEX for AMPL can be obtained without charge through the IBM Academic Initiative; see our CPLEX download instructions for details.

Purchase CPLEX for AMPL Directly From Us

15 September 2010:
CPLEX for linear, quadratic, and mixed-integer programming has joined the lineup of AMPL-enabled solvers available for purchase directly from AMPL Optimization LLC. Version 12.2 is currently shipping. Contact us at info@ampl.com for pricing on single-user, floating, and server licenses. Full-featured trials are also available.

Gurobi 3.0 for AMPL Now Available

15 April 2010:
Gurobi version 3.0 for linear and mixed integer programming is now available for purchase with an AMPL interface, both directly through us and from Gurobi Optimization.

Purchase Gurobi for AMPL Directly From Us

21 May 2009: The new solver
Gurobi for linear and mixed-integer programming will be supported by AMPL. Gurobi binaries incorporating the AMPL interface will be available for purchase directly from AMPL Optimization LLC, together with AMPL for new users, and separately for current users of AMPL with other solvers. We will also offer free student versions restricted to 500 variables and constraints, and unrestricted 30-day trial licenses.

Orders are being taken now, and shipments will begin in June. For a listing of commercial or academic prices, contact us at info@ampl.com.

Purchase AMPL/MINOS and AMPL/SNOPT Directly From Us

7 April 2008: Two
Systems Optimization Laboratory solvers — MINOS and SNOPT — are now available for purchase with AMPL interfaces directly from AMPL Optimization LLC. Both are general-purpose solvers for large-scale smooth optimization problems having linear or nonlinear objectives and constraints. Each uses specific optimization methods that have varying strengths for different kinds of problems. Comparisons can be made by submitting AMPL problems to the NEOS Server or by arranging through us for short-term trial licences.

We make available the full AMPL/MINOS and AMPL/SNOPT packages in binary form, and also the solver part of each package for those who have already licensed AMPL. For a listing of commercial or academic prices, contact us at info@ampl.com.

Support for new features in CPLEX 11

1 February 2008: AMPL's communications with CPLEX have been enhanced to add support for two major features introduced in the new version 11:

  • A solution pool allows more than one solution to be returned from a single run of the branch-and-cut solver for mixed-integer programming.

  • A tuning algorithm automatically runs the branch-and-cut algorithm repeatedly with different combinations of algorithm parameters, and reports back on the best results found.
AMPL cplex_options directives have also been added to request or control a variety of features new to CPLEX 11, including zero-half cuts, a feasibility-pump heuristic, "dynamic search" as an alternative to traditional branch-and-cut, alternative node relaxations for solving quadratically constrained mixed-integer problems, and choice of deterministic and opportunistic modes in parallel optimization. For an updated account of all CPLEX options controllable through AMPL, see the summary in
README.cplex and the ILOG AMPL CPLEX System 11.0 User's Guide.

Support for new features in KNITRO 5.1 and CPLEX 10.1

30 November 2006: AMPL has added support for features introduced in recent versions of these two solvers. Our INFORMS Pittsburgh
slides show a variety of examples.

KNITRO has been extended to accept optimization problems that incorporate any of AMPL's complementarity constraints. Other recent options include Hessian-vector products to speed derivative calculations, a crossover procedure to make complementarity of the solution more exact, and a multistart facility that tries multiple random starting points to search for improved results.

CPLEX allows for indicator constraints that specify implications directly by means of a ==> operator rather than indirectly by use of formulation tricks involving zero-one variables. Also certain problems that have very large collections of equations or inequalities can benefit by declaring many of them to be lazy constraints or user cuts. Enhancements for mixed-integer programming that can be requested from AMPL include taking advantage of infeasible MIP starting solutions, automatic MIP symmetry-breaking, re-applying presolve after root processing is complete, and attempting to polish the current solution at the end of the procedure. Also added is a mechanism for returning a meaningful solution when the problem is infeasible.

AMPL Studio Graphical Interface and AMPL COM Objects Now Available

11 January 2006:
AMPL Studio is a new AMPL product that offers a graphical user interface to AMPL and to several solvers, including FortMP, CPLEX and MINOS. It provides for viewing multiple model, data, and result displays, and for organizing AMPL files into projects and workspaces. All AMPL commands remain available through command-entry and console windows. AMPL Studio is available from OptiRisk Systems, who also offer a collection of COM Objects for embedding AMPL into Windows applications.

AMPL Newsgroup Established at Google.com

8 August 2005: Post questions, give advice, or search the archives at our newly established newsgroup. To browse postings, visit our group home page. To have postings automatically mailed to you, indicate your preferences at our group join-up page or enter your email address in the Google box on the AMPL home page.

Purchase AMPL/KNITRO and AMPL/CONOPT Directly From Us

19 December 2004, 24 July 2004: The AMPL/
KNITRO and AMPL/CONOPT nonlinear solvers are now available for purchase directly from AMPL Optimization LLC. Both are general-purpose solvers for large-scale problems having nonlinear objectives and/or constraints. Each uses specific optimization methods that have varying strengths for different kinds of problems. We can arrange trial licenses for benchmarking.

We make available the full AMPL/KNITRO and AMPL/CONOPT packages, and also the solver part of each package for those who have already licensed AMPL. For a listing of commercial or academic prices, contact us at info@ampl.com.

Purchase AMPL Directly From Us

31 May 2004: AMPL is now available for purchase directly from AMPL Optimization LLC. For a listing of commercial or academic prices, contact us at

For those who have obtained AMPL from other sources, or are connecting AMPL to their own solvers, we are selling standalone copies of AMPL. We are also announcing the availability of AMPL/solver packages, beginning with AMPL/CONOPT and AMPL/KNITRO (see above). Additional AMPL/solver packages remain available from our vendors.

AMPL Optimization LLC Assumes
Responsibilities for AMPL Development and Support

14 July 2003: Following an agreement recently concluded with Lucent Technologies, Inc., responsibility for development and support of the AMPL modeling language and system has been assumed by AMPL Optimization LLC, a new company formed by the inventors of AMPL. Lucent is the corporate parent of Bell Laboratories, where Robert Fourer, David Gay, and Brian Kernighan initiated the AMPL project in 1985.

The newly concluded agreement anticipates that current AMPL vendor agreements will be assigned to AMPL Optimization LLC. Thus initially AMPL sales and maintenance will continue to be available from existing vendors.

Also under the new agreement, the ampl.com internet domain and AMPL trademark have been transferred to the new company. Further developments will continue to be announced on the AMPL home page.

AMPL Plus Student Edition expired at the end of 2002

1 January 2003: Due to the expiration of an embedded CPLEX license, copies of AMPL Plus for Windows that were distributed with the AMPL book expired on January 1, 2003. Current users should download a standard (command-line) student edition for Windows, following the instructions on the AMPL download page.

New graphical user interfaces for AMPL are under development. You can currently download copies of several experimental GUIs, but release dates for finished products are still to be set.

AMPL Book 2nd Edition

8 November 2002: A second edition of AMPL: A Modeling Language for Mathematical Programming is now available. It contains updated versions of all of the material in the first edition, plus new chapters on database and spreadsheet interactions, command scripts, solver communications, and complementarity problems. All of the new features described at this web site in mid-2002 or earlier are now covered in the book.

CPLEX 8.0 Student Edition for AMPL

8 October 2002: Users of standard (command-line) AMPL can now download an AMPL student edition of the new version 8.0 of CPLEX. Like other AMPL student editions, this AMPL/CPLEX is full-featured but limited to 300 variables and 300 constraints.

If you're new to AMPL, you might want to take a look at the quick start instructions on our downloads page. Windows users can now get the Student Editions of standard AMPL, CPLEX 8.0, and MINOS 5.5, plus the Kestrel client for internet access to solvers and a table handler for database access to data, by downloading and unpacking a single archive file.

(The AMPL Plus Student Edition expired at the end of 2002 as described in the the January 1, 2003 item above.)

Student Edition software licenses must be updated for 2002

7 December 2001: The Student Edition of AMPL Plus 1.6 that is packaged with the AMPL book will not work after December 2001. To continue using this software, you must download and install an updated version that will continue to work through 2002.

To carry out this update, download the files readme.txt and setup.exe. Then run (double-click) setup.exe and follow the directions that appear. All of the files needed to keep running the AMPL Plus 1.6 Student Edition will be unpacked and written to a folder you can specify, ready for use. It is OK for this folder to be the same one you have been using for AMPL Plus, but in this case any files you have changed since first installing AMPL Plus will be overwritten. More installation details appear in readme.txt

The availability of AMPL Plus and other AMPL student versions after 2002 is currently under negotiation. Developments will be reported on the AMPL home page.

The main advantage of AMPL Plus is its Windows-style graphical user interface. If you do not require this feature, you can download a command-line version of the AMPL Student Edition that has no expiration date.

AMPL Remote Access via NEOS and Kestrel

16 July 2001 (updated 12 October 2001): The NEOS Server accepts AMPL input to over 20 solvers of various kinds, through web, e-mail, and socket-based interfaces. These services are available free of charge to anyone who has the requisite Internet connections. They are intended mainly for testing, prototyping, and instructional purposes where a guaranteed schedule or volume of computing resources is not essential, but currently uses for any legitimate purpose are permitted.

Kestrel, a new interface to NEOS, permits you to use many of the NEOS solvers -- currently 9 in all -- through the usual solve command in an AMPL session, with results returned for display and processing within the AMPL environment. Currently supported for Windows, Linux, and Sun's SPARC Solaris, Kestrel is implemented as a single executable file that takes over the role of the local solver at a traditional AMPL session.

The Try AMPL web interface to the AMPL Student Edition and solvers also remains available.

MOSEK AMPL Vendor and Solver Link

16 July 2001: EKA Consulting ApS, based in Copenhagen, Denmark, now sells AMPL in addition to their optimization products.

7 September 2000: EKA Consulting has added an AMPL interface to their MOSEK Optimization Tools. MOSEK includes a simplex method for linear programs and an interior-point method for linear, convex nonlinear, and convex quadratically constrained optimization problems.

Relational Database Support

15 June 2000: A flexible new table declaration defines correspondences from AMPL data and results to relational database tables maintained by other software. New read table and write table commands use these correspondences to move information between AMPL and databases. Communication with external database software is managed by plug-in "handlers" that can be loaded as needed.

A new writeup on Relational Database Access explains the principles and operational details of this feature. You can try it out now by using the standard (command-line) AMPL Student Edition in conjunction with a handler for the Open Database Connectivity (ODBC) standard under Microsoft Windows; see Downloading the standard AMPL database handler for instructions. This handler supports Microsoft Access and Excel and any other database software for which an ODBC driver is installed.

To upgrade the standard AMPL Professional Edition software with relational database support, contact your AMPL vendor. As vendors release new AMPL versions that provide this support, their availability will also be announced on this web site.

(The standard AMPL database features are independent of the database access facilities in the AMPL Plus Professional Edition.)

Scrolling Window Utility for Windows

15 June 2000: Microsoft Windows users who have been running standard (command-line) AMPL in an "MS-DOS" window can now switch to sw.exe, a utility that provides a more convenient scrolling window with facilities for cut-and-paste and font selection. See Downloading the "Scrolling Window" utility for instructions.

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 Amazon.com, 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 dtabase 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 Amazon.com 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.

Comments or questions?
Write to info@ampl.com or use our comment form.

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