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NEOS Interfaces to Ipopt

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The NEOS Server offers IPOPT for the solution of non-linear programs in AMPL format. IPOPT is an open source software package for large-scale non-linear optimization. It implements a primal-dual interior point algorithm, which uses a filter line search method to ensure global convergence.

More information on IPOPT is available from the IPOPT home page. A technical report describing the algorithm can be downloaded here.

IPOPT has been developed by Andreas Wächter, Lorenz T. Biegler, Arvind Raghunathan, and Yi-Dong Lang.

Using the NEOS Server for IPOPT

The user must submit a model in AMPL format to solve a non-linear program (NLP). Examples of models in AMPL format can be found in the netlib collection. A large collection of NLPs modeled in AMPL can be found at Bob Vanderbei's website.

The model is specified by a model file, and optionally, a data file and a commands file. If the command file is specified it must contain the AMPL solve command.

The commands file can contain any AMPL command, and may set options for IPOPT, for example

option ipopt_options "imaxiter=1000 dtol=1e-6";

Printing directed to standard out is returned to the user with the output.

Having a rich, realistic testset is of paramount importance for the evolution of optimization solvers. Therefore, models submit to NEOS for solution with IPOPT may be used by the authors for testing and improvement of their code.

Enter the location of the ampl model (local file)
Model File:

Enter the location of the ampl data file (local file)
Data File:

Enter the location of the ampl commands file (local file)
Commands File:


Dry run: generate job XML instead of submitting it to NEOS
Short Priority: submit to higher priority queue with maximum CPU time of 5 minutes
e-mail address:

By submitting a job, you have accepted the Terms of Use
Please do not click the 'Submit to NEOS' button more than once.

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