Everyone! The NEOS Server is open free to the public. Some of the solvers may limit use, however.

Check out the AMPL FAQ.

We do not offer any of the optimization solvers we let you use through the Server for download from the Server site. Some of these solvers are commercial to varying degrees, but we are allowed to offer them for your use through the Server free-of-charge. To find out more about them, follow any links on the Web page for the solver, or do a Web search on the solver or name of the developer. If you cannot find anything, we may be able to help, but often we know no more about it than you do.

First, you need to have your optimization problem formulated in one of the input formats accepted by a solver. Look through the solvers on the server-solvers page to see what formats are available for your type of problem. Most of the solvers have links to pages or Web sites that explain the syntax of their input format. Once you have your input files ready, you can go to the Web Form link on the solver page, fill in the names of your files and any other information, and submit your job to the Server. Later, you may look at the E-mail option or the Submission Tool for Unix or Windows (or Macintosh when it has a good Java runtime environment implementation).

The NEOS Submission tool is a high speed, socket-based interface for UNIX workstations that provides easy access to all the optimization solvers available with the NEOS Server. This tool allows users to submit problems to the NEOS Server directly from their local networks. Results are displayed on the screen.

Yes! NEOS does not allow you to compress your entire submission, but if you want to compress the files individually (to accommodate large data files, for example), you can submit them via the Web or Submission Tool interfaces. The NEOS Server checks each file to see whether it is compressed, so you can compress any data for which the interface has a Browse option. The compression types the Server supports are standard deflation for .gz,.z,.zip, and .Z files.

At the bottom of the list of solvers are the Administrative solvers. Kill Job is the one you are looking for, but you will need your job number and password.

From the main Server Web page, click on the check progress link.

First of all, always give your email address so that the results can be sent to you more reliably. Sometimes when the execution takes a long time without producing any output, the Web server will cause the CGI script to time out. If you save the job password and number and enter them in the admin form, it will give you intermediate or final results. If more than one day has passed since the job finished, however, the file with your results may have been deleted. Again, always give your email address for results forwarding.

Do not try to include your model or data files by name in the AMPL commands. The files are given new names under NEOS and will be loaded automatically.

If you have your own copy of the GAMS or AMPL modeling language software, then you can use GAMS or AMPL to read your files locally, before sending your problem to NEOS. Also you can have the results returned to your local GAMS or AMPL environment, wehre you can write whatever files you need. See the description of the Kestrel client for an explanation of how this works.

To transfer information between local text files and NEOS, you can also use the NEOS XML-RPC interface. If you have Python installed (see the Python download instructions) then you can write simple programs to make the transfers. Here�s an example of a program for writing NEOS�s text output to a file:

----------------- getresults.py ----------------- 
#!/usr/bin/env python 
# usage: getresults.py jobnumber password outputfile import sys import xmlrpclib

neos = xmlrpclib.ServerProxy("http://neos-1.chtc.wisc.edu:3332")
jobNumber = int(sys.argv[1])
password = sys.argv[2]
outfile = sys.argv[3]

status = neos.getJobStatus(jobNumber,password)
if status == "Bad Password":
  sys.stdout.write("Bad password\n")
  sys.exit(1)
if status != "Done":
  sys.stdout.write("Job %d not done yet\n" % jobNumber)
  sys.exit(1)

out = open("outfile","w")
results = neos.getFinalResults(jobNumber,password).data
out.write(results)
out.close()

Web servers place restrictions of the amount of data that can be uploaded. You should not have this problem if you use email or the Submission Tool. Some of the solvers have limits on the amount of data they can process, though.

Congratulations, you got the format for the submission correct, and it was passed on to the solver. Usually a runtime error means that the solver found a syntax error or a floating point exception like an overflow or a subscript out of bounds. This type of error should be detected by the solver, which will give an error message about the problem. We would appreciate hearing about it when the solver dies without any message. Please send an email to the solver administrator via the neos-comments screen for the solver page, mentioning the job number, the submission interface you were using, and including the submission itself.

Check that the file you sent in contained no non-ASCII formatting symbols from a composer such as Word or Word Perfect. By saving your documents as .txt files, you should be able to get rid of the formatting symbols.

Models run from GAMS have a default limit of 1000 seconds. This can be extended on a per model basis by adding the statement: modelname.reslim = 2000; before the solve statement. Here modelname is the name of the model, whose time limit is extended to 2000 seconds by this directive.

For Web submissions, the maximum number of bytes that may be submitted is currently 1048576 bytes. The limit for email submissions is set by our mail server (100000 bytes), which may change without our knowledge. The Submission Tool has no hard-wired limit, but the NEOS Server will not send a job larger than 16777216 bytes to any solver station.

The NEOS server was not designed with the capabilities of a mail server, and the fact that it must use, and not merely display, email data limits the formats it can accept. If the first line cannot be parsed correctly, you should receive mail from the server with the offending line and the entire message below. There have been times, however, when the server could not respond to an email message at all. I suggest submitting a small test problem to see if the server can understand your mailer. You may choose one of the sample files on a "Sample Submission" page to send. They usually run only a few minutes.

You may need to refresh the NEOS pages in your browser. We are not above moving things around and have no way to give notice to people not on the neos-news mailing list. Also, solver administrators may choose to disable their solvers at any time without notice.

Not necessarily. We've had problems like this in the past when the user data contained lines with only TAB characters in them. Try to make sure none of your files contain TABs, which can be added automatically by your editor. A strange fix, but it's worked before.

Your Fortran objective function can call other subroutines, but if the solver you are using indicates only one file, then the subroutines must all be located in that one file.

Citing the first three works below should cover it.

The paper by J. Czyzyk, M. Mesnier, and J. Moré, The NEOS Server, which appeared in IEEE Journal on Computational Science and Engineering, 5 (1998), pages 68-75, discusses the design and implementation of the NEOS Server.

The paper by W. Gropp and J. Moré, Optimization Environments and the NEOS Server, that appeared in Approximation Theory and Optimization, M. D. Buhmann and A. Iserles, eds., pages 167-182, Cambridge University Press, 1997, discusses the NEOS Server as a problem-solving environment that simplifies the formulation of optimization problems and the access to computational resources.

The technical report by E. Dolan, The NEOS Server 4.0 Administrative Guide, Technical Memorandum ANL/MCS-TM-250, Mathematics and Computer Science Division, Argonne National Laboratory, May 2001 discusses the Server implementation and use in detail. The paper is available for download in compressed postscript format.

The paper by M. Ferris, M. Mesnier, and J. Moré, NEOS and Condor: Solving optimization problems over the Internet, discusses the use of Condor, a distributed resource management system, as a provider of computational resources for NEOS. You can download the paper in a compressed postscript format.

The paper by E.D. Dolan, R. Fourer,J.J. Moré, and T.S. Munson The NEOS Server: Version 4 and Beyond takes a look at advances in the server in 2001, including the Kestrel interface. You can download the paper in PDF format.

The technical report by E.D. Dolan and T.S. Munson offers a user's guide to the Kestrel interface.You can download it in Postscript or PDF format.

The article by E.D. Dolan, J.-P. Goux, R. Fourer, and T.S. Munson gives details of the design and use of the Kestrel interface to the server. You can download the paper in PDF format.

We are currently using ADIFOR for Fortran programs, and ADOLC and ADIC for C programs. Consult A Collection of Automatic Differentiation Tools for additional information on automatic differentiation tools.

The first step is to contact us by sending email to support@neos-server.org. We are interested in adding solvers that add new capabilities to the Server. The process for adding solvers is described in the NEOS Solvers Documentation.