NEOS Server Home

NEOS Interfaces to Ipopt

Sample Submissions
WWW Form - Email - XML-RPC


The NEOS Server offers IPOPT for the solution of nonlinear programs. Problems can be submitted to IPOPT on the NEOS server in AMPL or GAMS format.

IPOPT is an open-source software package for large-scale nonlinear optimization. It implements a primal-dual interior point algorithm, which uses a filter line-search method to ensure global convergence.

The main authors of IPOPT are Andreas Wächter and Carl Laird, with additional development by Lorenz T. Biegler, Arvind Raghunathan, and Yi-Dong Lang. For more information, see the IPOPT home page. A list of papers and publications describing the algorithm is available here.

Using the NEOS Server for Ipopt/GAMS

The user must submit a model in GAMS format to solve an optimization problem. For security purposes, the model submitted must adhere to the following conventions:

If you are unfamiliar with GAMS, the GAMS Documentation includes a GAMS Tutorial and User's Guide. Examples of models in GAMS format can be found in the GAMS model library.

By default, the NEOS Server limits the amount of output generated in the listing file by turning off the symbol and unique element list, symbol cross references, and restricting the rows and columns listed to zero. This behavior can be changed by specifying the appropriate options in the model file. See the documentation on GAMS output for further information.

You may optionally submit an options file if you wish to override the default parameter settings for the solver. Currently, the NEOS Server can only use optfile=1 with GAMS input. Therefore, any model that specifies a different options file will not work as intended.

Web Submission Form
Model File
To submit a nonlinear programming problem specified in the GAMS modeling language, you need to specify the absolute path to the GAMS file on your system.
Options File
The Options file is optional and requires that the statement <modelname>.optfile = 1 ; exist before the solve statement in your model file. Only optfile = 1 is supported, however, options also may be specified within the model input file (see the GAMS documentation).
GDX File
The GDX file is an optional file for inputs. It will be renamed in.gdx. The model must include "$GDXIN in.gdx" to load this file.
Return GDX output
Return log file
You may enter any additional comments here, for example, to identify the data for your own information. These comments will be returned with your results.
Additional Settings

E-Mail address:
Please do not click the 'Submit to NEOS' button more than once.