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NEOS Interfaces to AlphaECP

Sample Submissions
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The NEOS Server offers AlphaECP for the solution of mixed-integer nonlinear optimization problems. Problems for AlphaECP can be submitted on NEOS Server in GAMS format.

AlphaECP is based on the extended cutting plane (ECP) method, an extension of Kelley's cutting plane method, which was originally given for convex NLP problems. The method requires only the solution of a MIP subproblem in each iteration. The MIP subproblems can be solved to optimality, to feasibility or to only an integer-relaxed solution in intermediate iterations. This makes the ECP algorithm efficient and easy to implement.

AlphaECP was developed by Tapio Westerlund and Toni Lastusilta of Abo Akademi University in Finland.

For further information on AlphaECP and GAMS, please visit the AlphaECP/GAMS Documentation website.

Using the NEOS Server for AlphaECP/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 mixed-integer nonlinear optimization problem specified in the GAMS modeling language, you need to specify the absolute path to a 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

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