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NEOS Interfaces to JAMS

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JAMS

The NEOS Server offers EMP (Extended Mathematical Programming), an (experimental) framework for automated mathematical programming reformulations through the solver JAMS. Models that cannot be solved reliably are reformulated into models of established mathematical programming classes in order to use advanced solver technology.

EMP supports the modeling of Bilevel Programs, Variational Inequalities, Disjunctive Programs, Extended Nonlinear Programs and Embedded Complementarity Systems. The reformulation is done by the solver JAMS, which is currently the only solver that is capable of handling EMP models.

The GAMS EMP Library, which is included in the GAMS Distribution, includes examples demonstrating how to use the EMP framework and the solver JAMS. JAMS is included free of charge with any licensed GAMS system but needs a subsolver to solve the generated models. Additional information on EMP can be found on wikipedia.

EMP has been developed jointly by Michael Ferris of UW-Madison, Ignacio Grossmann of Carnegie Mellon University, and GAMS Development Corporation.


Using the NEOS Server for JAMS/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 an EMP 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.
Comments
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.