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.
The user must submit a model in NL format. The NEOS Server will automatically handle an NL model in either binary or text format. NL files in either format can additionally be zipped, gzipped, or tarred prior to submission if desired.
An options file can optionally be specified. Please note that certain options may be restricted, altered, or removed by the NEOS server prior to solving. For example, users are limited to a max of four solver threads -- requests for more threads in the options file will not be honored.