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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

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

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

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 here:

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

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 AssumesResponsibilities 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 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.