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NEOS Interfaces to AlphaECP

WWW Form & Sample Submissions


The NEOS Server offers AlphaECP for the solution of mixed-integer nonlinear optimization problems 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.

Documentation for AlphaECP is available on the GAMS Documentation website. AlphaECP is developed by Tapio Westerlund and Toni Lastusilta of Abo Akademi University in Finland.

Using the NEOS Server for AlphaECP

The user must submit a model in GAMS format to solve a mixed-integer nonlinear 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 must not execute external programs, i.e., no $call or execute statements.
  • It must not create files, i.e., no put files or $echo statements.
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 and an alphabetical index is also available.

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 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
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.