NEOS Server Home

NEOS Interfaces to Knitro

WWW Form & Sample Submissions


The NEOS Server offers Knitro for the solution of general mixed-integer nonlinearly constrained optimization problems that can be modeled in GAMS format. Knitro also can be used to solve simpler classes of problems, such as unconstrained problems, bound constrained problems, linear programming (LP) problems and quadratic programming (QP) problems.

Knitro was developed by Richard Byrd, Mary Beth Hribar, Jorge Nocedal and Richard Waltz with additional help from Guanghui Liu, Marcelo Marazzi, Todd Plantenga and Jose Luis Morales. For a detailed description of Knitro, see R. H. Byrd, J. Nocedal, and R. A. Waltz. 2006. KNITRO: An Integrated Package for Nonlinear Optimization. In: G. di Pillo and M. Roma, editors. Large-Scale Nonlinear Optimization. Springer-Verlag. p. 35-59.

Knitro is available from Artelys. For more information on Knitro, see the Knitro website.

Using the NEOS Server with Knitro

The user must submit a model in GAMS format to solve a mixed-integer nonlinearly constrained optimization problem. For security purposes, the model submitted must adhere to the following conventions:
  • It must be self contained, i.e., no $include or $batinclude statements.
  • It may not execute external programs, i.e., no $call or execute statements.
  • It may not create files, i.e., no put files or $echo statements.
If you are unfamiliar with GAMS, the GAMS Documentation Center provides a GAMS User's Guide. Examples of models in GAMS format can be found in the GAMS model library and an alphabetical index is also available.

An options file can be used to specify Knitro options. 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.

The NEOS Server initially 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 the modeling language for further information.

Web Submission Form
Model File
To submit a mixed-integer nonlinearly constrained optimization problem, 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 ; exists before the solve statement in your model file. At this time, only optfile = 1 is supported; however, options may also 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
If the box is checked, the solver will return a compressed GDX file that contains all symbols in the model.
Return log file
If the box is checked, the log file containing information generated by the solver will be returned with the output.
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
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:
Please do not click the 'Submit to NEOS' button more than once.