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I would like to compliment you on an excellent site - that simplifies solving semidefinite programs a lot without installing software.
I am currently trying to estimate horizontal wavenumbers using complex pressure measurements collected from a horizontal towed array for my PhD dissertation at the University of Rhode Island. The idea is to estimate the wavenumbers and use the "wavenumber gradients" to identify the best environments for use in matched field processing. I am currently trying to use the conjugate gradient Fortran software (CGPLus).
NEOS did a great job! I am currently a graduate student. I used CGplus to solve the conjugate gradient problem as my assignment. I really needed such a website as a helper and reference.
I'm using NEOS for a class homework in a graduate NLP course, just to have the students get the feel for the possibilities of numerical solution and the great service that NEOS provides! They'll just do a toy problem for the homework, because they come from lots of different backgrounds, I can't teach them all AMPL, etc. But I think it will still be instructive!
I am very pleased with your valuable AMPL service. I have been an AMPL user for more than seven years, since I used it to run the programs of my PhD dissertation. Now, with your Internet service, I have the opportunity to teach my students and let them run real AMPL cases. I will also use it in doing research.
I have used the NEOS and minlp solver running in the background to resolve a small model on my research. It is quite great, if I have chance I would like join into this system as well.
I'm very satisfied with the job done... fast enough. Its for solving an assignment for education purpose(a graduate-level course).
I have been using the mixed-integer solvers at NEOS to study the complexity of phase retrieval, a problem encountered in several disciplines, principally crystallography and astronomy. My NSF grant has a budget for computer software, but not in the amount required to purchase some of the high end optimization software at NEOS. Another benefit provided by NEOS is that I am able to do serious number crunching from my humble laptop.
NEOS has been a very valuable tool in the two graduate optimization courses that I regularly teach: CS 719 Network Flows and CS 720 Integer Programming. NEOS allows students to see a broader variety of solvers than we have available in the Computer Sciences Department at the University of Wisconsin - Madison, and also helps to overcome a variety of time/storage limits that apply to student jobs here. For example, the student version of AMPL packaged with the text for CS 720 allows at most 300 constraints and 300 variables, but several students in the course are doing course projects involving problems that are substantially larger than those limits.
I have been teaching a course on linear and integer programming over the past two months. Part of the course is based on projects where the students use GAMS. Previous years, they have used the student version of GAMS to model the project problems. This year, I have given them larger problems where they have sent their GAMS files to NEOS and used XPRESS-MP to solve the problems. The ability to use GAMS and not being limited in size by the student version has been extremely useful. I find NEOS a very useful tool for teaching this course. When the students leave the course, they know how to build a GAMS model, and they also know that they can solve large problems via NEOS.
-- Royal Institute of Technology, Stockholm
We very much appreciate the NEOS server service. We find that not only are the solvers and the software reliable, but also that the people maintaining and developing the codes are very helpful. The NEOS server provides the possibility to run problems without going through the whole process of installing a software package, paired with the possibility to run instances on powerful machines.
At the university of Cologne we are interested in finding good bounds on the maximum cut value in sparse graphs. This problem has an application in theoretical physics and is interesting to the physicists' community. We calculate an upper bound on the exact value of the maximum cut by formulating it as a positive semidefinite program. We then add valid inequalities to tighten the relaxation. We solve the resulting problem exactly with the solvers CSDP and SDPA.
I am a PhD student at the University of Melbourne, Australia. Recently, I have been using NEOS (solvers:PATH, DONLP2, FILTER, MINOS) to carry out some numerical tests on a game theory model arising in currently debated electricity restructuring. A big thank you to NEOS staff for providing such a wonderful facility (free!).
Excellent tool! I am using it for academic research regarding route selection in packet switched networks. I had no prior experience in the gams language but was able to quickly hack together a series of equations that the nlp solver was able to give me good results with.
I would like to thank all the people who provide and maintain NEOS. At the beginning of this summer I began a term of assisting a professor at my university with his research. The daunting task of solving nonlinear programming problems was put on my shoulders and I felt as though I was in over my head. I didn't even know what nonlinear programming was and after I discovered what it was, it became clear how enormous a task it would be to solve the problems assigned to me. I bought Maple 6 to try to help me, but the calculation times were huge, as well as the round off error. Then looking for a better way, I found NEOS. With the great abundance of help given me by the caretaker(s) of NEOS, it took a short while to figure out how to setup the input file (I used AMPL format). I had extremely complicated objective functions, both convex and nonconvex, an arm load of variables, and an armload of convex, nonconvex, equality and inequality constraints, but when I sent off the information via the web submission form, within seconds I received extremely accurate and consistent results. The results were used for verifying a certain theory in my professor's research and so accuracy was extremely important. It has been an invaluable service to me and I truly doubt that I could have done my job to the satisfaction of my professor. I would highly recommend NEOS to anyone needing constrained optimization calculations done quickly and accurately.
I am a graduate student at RPI in Troy, NY working on non-linear polymer diffusion in confined spaces. Specifically, I am attempting to find solutions to the modified Cahn-Hilliard equation, a fourth order partial differential equation by techniques to minimize the total free energy of the system. While these problems are certainly not as complex as the large scale process optimization studies performed by other groups, the NEOS system using the Lancelot solver has allowed me to spend more time on experimental work that is also of interest to us since the optimization routines are made easier to use than if I had to write them myself. The submission process is straightforward and the availability of the NEOS solver has allowed me to concentrate more on the physics of our problem than the mechanics of writing optimization codes. If programs like the IBM data visualization explorer and HDF were made as easy to use as the optimizers from ANL, I would be ecstatic. As it is, I would encourage the continued funding of the NEOS server at ANL and its related costs. The service has been a great help in my progress toward a doctorate.
This is a great resource for those of us who need to demonstrate large scale optimization to students, but who do not have enough need for this (or funds!) to justify the purchase of a large scale optimization package.
I have been using NEOS in my nonlinear programming course every spring semester. We use the student version of AMPL earlier in the semester, and then I assign a larger applied problem (that is too large to be handled by the student version), which the students are asked to model with AMPL and then solve. In the past I have used AMPL and MINOS, but in future semesters I plan to ask students to compare different solvers. I have also used NEOS in assisting a non-optimization colleague of mine to solve optimization problems relating to database design.
Hi, I've been using your server to solve complementarity models of electricity markets (using the PATH solver and AMPL). This is academic research. Following is an abstract of my paper. Your site has been invaluable for me. Keep up the good work.
This paper presents a modeling framework for analyzing competition between multiple firms that each possess a mixture of hydroelectric and thermal generation resources. Based upon the Cournot concept of oligopoly competition, the model characterizes the Cournot equilibrium conditions of a multiperiod hydro-thermal scheduling problem. Using data from the western U.S. electricity market, this framework is implemented as a mixed linear complementarity model. The results show that some firms may find it profitable to allocate considerably more hydro production to off-peak periods relative to peak periods. This strategy is a marked contrast to the optimal hydro-schedules that would arise if no firms were acting strategically. These results highlight the need to explicitly consider profit maximizing behavior when examining the impact of regulatory and environmental policies on electricity market outcomes.
I had a large very non linear problem. I used NEOS because of the AMPL interface and the access to various solvers. Originally I had no luck because the problem was just too large. I condensed it to one with about 11000 variables and 11000 constraints, of which about 10000 variables and 3000 constraints were nonlinear. After considerable work on the parameters, MINOS solved many variations of the problem in about ten minutes elapsed time each. I'd like to thank the NEOS team for their prompt and helpful attention to some queries I had. It was great to have the opportunity to try my problems on a number of different solvers, although in the end, MINOS proved the most useful solver for this set. I also found the web interface and email results made it easy to run a large project remotely and the overall documentation is an excellent introduction for beginners to math programming.
I used the solver CSDP via NEOS to solve several dozen semidefinite optimization problems. These SDPs were very large, typically with over 100 variables and several thousands of constraints. I found that the NEOS system was easy to use and quite reliable. I would certainly consider using it again in the future, as well as pointing it out to other people whose work also requires solving optimization problems. Thank you again for setting up NEOS and for keeping it running!
We (my students and I) have been solving large semidefinite programs (SDPs) using both SeDumi and CSDP solvers. Both have worked excellently. We have been able to solve some very large problems. The problems arise from relaxations of quadratic assignment problems.
I just would like to thank you all for the neos server: it's just perfect. I learned AMPL to use the server and this was useful for its own sake. Now I use the server for teaching, letting the students to put hands on simple parametric optimizations. Moreover I use the server to solve problems for research purposes.
One of the main motivations was the ability to run very large (more than 1M arc) network flow problems. Student accounts here have rather limited memory allocations, and many students had problems just storing the input data files for 1M arc problems (and the storage for the temporary files used by the algorithms is several times larger than the input). I wanted
students to develop an awareness of the size of the problems that network codes can solve, and this would have been hard to do locally. Additionally, I wanted students to develop a feeling for the relative speed of various network and general LP codes. NEOS provides easy access to 2 different network algorithms (both of which I teach in my course) as well as LP codes. This aspect I could have handled locally (with problems much smaller than 1M arcs), but students are generally reluctant to learn multiple interfaces, so it was very convenient to do it all via NEOS.
I think that first we all should thank you and your colleagues for the excellent work done with NEOS. It is a great service to the public. I myself used it in trying out the AMPL interface for my code donlp2, most of the other codes being installed locally here. But I know of a colleague which uses NEOS as a teaching machinery for his nonlinear programming courses, which could otherwise be done only by paper and pencil due to the lack of appropriate computing resources.
I sincerely believe "optimization on the Internet", or some people refer to it in more general terms: "providing decision technologies over the Internet as services", is very important and will become ever more important in the future. For "optimization" to become a viable tool for the "end users", they must be provided with the latest optimization tools in a user friendly manner. NEOS relieves the end users from "software version updating" headaches and provides very friendly and expert guidance on their problems. I thank you for an excellent service.
I require students in my senior project course to study OTC thoroughly and solve some optimization problems making use of the NEOS services. These problems can be solved with the software available in our university, but I do this in order to provide students with some experience on use of Internet for long distance technical collaboration. I also believe resources like OTC are excellent means for continuing professional development for my students.
I am using NEOS for solving problems and examples for the classes I teach.
-- Faculdade de Ciencias da Universidade de Lisboa, DEIO
Thank you very much for BonsaiG. I used it for my master's thesis at the University of Twente, where I scheduled iterative algorithms on multiprocessor systems.
We are using the NEOS Server to design communication networks and system state perception of control agents for large, distributed networks, such as the power grid, at Carnegie Mellon University.
We are using the NEOS Server for teaching AMPL and SIF and solving tutorial examples of nonlinear optimization. Some students are using the NEOS Server for solving optimization problems when writing their Diplom-thesis. Thank you very much for managing the NEOS-Server.
Thank you so much for your works at the NEOS Server. We are using the NEOS Server for the research of Computer Network and solving the Network Design Problem at Osaka University in Japan.
I used NEOS for a project in a grad-level CS class at Purdue Univ this past fall, on a network flow problem.
I had students run some examples using NEOS in three classes since you first announced it. No one complained :-) The only difficulties I heard about we of the i've-never-programmed-in-Fortran variety, and those are not your issue. Valuable service.
We are planning to use NEOS with the (still experimental) callback features in inverse problems arising in multiphase reactionary fluid systems in an interdisciplinary research project at the University of Technology Aachen.
The only computation I have done using NEOS is for unconstrained NLP (NMTR), application to train an artificial neural network (in a project with an engineering student). I have also presented NEOS to third year undergraduates, to introduce them to optimization software for NLP especially, and referred 3rd parties to the NEOS web site. One of the main benefits of NEOS from my point of view is that it provides a kind of one-stop-shop for people tinkering with optimization models/methods, and is friendly enough for non-optimizers to get along with.
I am a graduate student at the University of Pittsburgh. I am using the Filter solver (Ampl input) to find nonlinear models for the boiling points of alkanes. This is part of my Ph.D. thesis and a paper we are writing that has been accepted for publication in the journal Match. We are planning to cite the website in our paper. Dr. Mihai Anitescu is serving on my thesis committee and directed us to your site.
I am a graduate student at the UC Davis applied math program, working under the supervision of Dr. Naoki Saito. It has been our pleasure to discover the power of NEOS. Currently we are using it to solve the sparse representation problem that comes up in neuroscience (study of the brain's representation system):
min SUM(||BX_k||) s.t. B'B = I
or an appropriate relaxation thereof. It comes up in the study of the "natural basis" for the human brain to represent images. The advantage of NEOS is that we can try different solvers to see which one is capable of solving our problem. Many thanks and keep it up!
I'm a PhD Student here in Spain. I'm frequently using the NEOS solvers since the beginning of this year, when I was told that they could be useful in maximizing a likelihood function which has not been implemented in any statistical package, so far. Indeed, they are very USEFUL and help me a lot. Colleagues already consult me in order to get to know the possibilities you offer via the internet. For the moment, I normally use the solver SNOPT for my programs written in AMPL, but I have to admit that, since [I am] a statistician, I need to reinforce my knowledge about the other solvers you offer. Summa summarum: THANK you very much!!!
I am a part-time graduate student at the University of Southern Mississippi. My research area is in solvers for systems of algebraic nonlinear equations. I first used MINPACK and have added LANCELOT (SIF), LANCELOT(AMPL) and MINOS(AMPL) to the solvers included in my studies. I have had success with LANCELOT in solving a problem that I could not with other solvers and I also use your solvers to verify the correctness of algorithms and other solvers that I am testing. I constantly use your NEOS Guide and the links that your sites provide have been very useful in all of my studies. I really appreciate the work that you have put into making your site extremely user friendly and you sharing all of your technical expertise.
Using the NEOS server in a class on Methods of Applied Math (Math511) at the Math.Dept., Univ. of Tennessee. It has been very useful. Keep up the good work!
We are using MINLP on the NEOS Server in a class on discrete design and optimization at University of Michigan. I cannot run the class without it!
We used the NEOS server for linear programming class at the University of Wisconsin-Milwaukee.
I used the NEOS server as part of my course "Computational Methods in Analysis" in both Fall 1998 and Fall 1999. There were 78 and 43 students enrolled, respectively. NEOS was used in a project to explore and evaluate methodologies for "delivering" math software to users. The students found that using the NEOS server was quite easy (although there are always a few people who seem never to be able to follow instructions) and they rated it as one of the more efficient ways to access existing software for the optimization problem they were assigned.
We are using the NEOS Server in a class on linear and nonlinear programming at Ohio University.
We have used the NEOS Server in a class for deterministic optimization in mathematical modeling at Saint Peter's College, NJ. I also use it in an elementary finite math class as a lecture demo.
I am teaching Optimization techniques for students who want become Diplom-Mathematiker. Our University is a University of Applied Sciences and for our students it is important to formulate and to solve optimization problems and it is not important to create new optimization techniques. Therefore I give only an overview about the different optimization techniques and then my students have to solve a wide variety of different optimization problems; linear and nonlinear. First the students are learning the MPS description of linear problems and then the are learning SIF. On our computers we have an old release of LANCELOT but I ask the students to solve the problems by using the NEOS server. Sending a problem to the NEOS Server, we usually received an answer in only few minutes. This is very good! I was also interested that my students use the helpful comments and suggestions on the various NEOS Web pages. The material is very good. My work is to be a moderator between the NEOS Server and my students - I think, the NEOS Server is a good [foundation] for "Computer Based Training".
I've been very impressed with the NEOS setup, so I'm taking some time to respond to your request. I've been using the GAMS-PATH (MCP) solver on NEOS to solve a CGE model for the South African economy, which is for my major project for a master's degree at Stellenbosch University, South Africa. The work is therefore educational. I'm trying to incorporate economies of scale and imperfect competition into an existing South African CGE model. If it works, I'll use it to analyze economic policy issues related to trade/industrial/competition policy. The model reasonably large (43 commodities, 43 sectors, 14 households), producing a system with just under 4000 variables. The work I'm doing would not at all be possible without NEOS, as I do not have access to fully functional GAMS software and the demo version of GAMS cannot deal with the models I need to solve. Our university wouldn't purchase a license, as there is not enough interest in such work, and my project is of course unfunded and relatively unimportant. Furthermore, the software is expensive, even when the GAMS developing country discounts are taken into account. So, I very much appreciate being able to use NEOS to solve my models and consider it very useful for small-scale researchers such as myself. It's not quite as convenient as having GAMS on your own PC, but certainly comes close enough :)
I am a graduate student major in business. I use NEOS for a course project in Operations Research Modeling. The problem is a linear program with about 400 variables.
We are using the server to give our MBA-students a problem oriented introduction to optimization. The students build small AMPL models and let NEOS do the computation. It is an extremely useful service for us, because we do not have to install any software in our computer labs.
Thanks for the prompt reaction! I am currently developing 100% Java application to aid students to learn operations research. Since the NEOS server is by far the best place on the web where my students can submit their applications with the hope of getting back trustable results, I am planning to integrate the communication module.
Lately I've been using the Neos server to solve large optimization problems formulated as semidefinite programs. Essentially, is a combinatorial problem that models the scheduling of thermal and hydro energy resources. This is part of my research work at the University of Waterloo in Canada. Because of the size of the test systems I've used, the neos server has been quite useful.
In my microeconomics principles class, I spend some time on cost minimization problems. Solutions to these problems are nicely illustrated by Neos. My students and I all appreciate having NEOS available to us.
Just a comment: you are doing an excellent job and an extraordinary service to the academic community. I am regularly suggesting my students to use NEOS as soon as their projects in AMPL cannot be solved with the student edition. So they debug their AMPL models locally with AMPLPlus (which unfortunately is no longer supported from ILOG - this is a great damage to the operations research community) and then they run their real-life projects thanks to NEOS. In my laboratory we have full versions of AMPL, CPLEX and MINOS, both on a PC and on a SUN server, but the students decidedly prefer to use NEOS from their lab or home PC. So: many many THANKS!
I am a great fan of NEOS, and try to spread the good news whenever I can. My most recent success was for an economics grad student from Oxford, whose thesis was to do with multi-person co-operation. He had a conjecture that something (I can't claim to understand the details!) that was true for two-person co-operation, might not be true for three or more. He managed to formulate this as a nonlinear program, that is if the NLP had a certain solution, his conjecture was true (the NLP was actually the discretized version of a continuous problem, and he wanted a fine discretization => a large NLP). Anyway, he struggled on his own ... until I pointed him to NEOS. Within a few hours, he had formulated his problem in AMPL, sent it to a variety of solvers (LANCELOT, MINOS, KNITRO, LOQO and SNOPT), interpreted the results, et voila, his conjecture was true. I believe he has just successfully defended his thesis!
Quite apart from the fact that NEOS is extraordinarily useful for people wanting to solve real problems, it is equally wonderful for those of us who try to design new algorithms. I adore the gladiatorial aspect, put your solver up on NEOS, and let it fight, naked, against the world's finest (of course, I can't pretend that the humiliating defeats for LANCELOT don't hurt, but the experience is invaluable for our next-generation solvers).
I would like to thank the organizers of NEOS for the wonderful construction which they have undertaken and which I find extremely efficient. My students, all fourth year majors in OR take my course in Mathematical Programming and are using NEOS to familiarize themselves with the best software available, which is invariably on your site. Thus, I would judge, but you should have machine data on this, that the favored software is Lancelot for constrained problems and CGplus, NMTR for the unconstrained case, the latter being a lot faster. The input into Lancelot which requires elemental and group function decomposition is a bit troublesome and it would be preferred to submit the functions in natural form. Probably this can be done, but we may have overlooked something.
We are also using NEOS for research and for thesis development. This is very important to us, as we can use the abundant routines given to try and document how the other routines fare, as you will notice, from our user statistics. In this we have a bit of a problem in writing one input, but we expect that the only common input to most routines is AMPL so we shall have to learn it. We will of course give due credit to NEOS as the papers that we develop appear in print, since we are extremely grateful to your institutions for such a great service to science and to research. I have neither kept a research diary regarding our use of NEOS, nor a didactic diary for my course, but as I find the NEOS is a great idea and extremely well implemented, I would be glad on my side to do anything that might be useful to you to help the project. Thus I would be glad to keep such diaries, if you expect ask for user accounting from time to time. I have not done it, since I was not expecting such a request, but I would be glad to do it. Otherwise I feel that my information will remain rather generic, although highly appreciative of the project.
NEOS is an extremely efficient computational tool and my classes of 14 students 4th year majors on OR following the course Mathematical Programming and a graduate class use it extensively to solve problems and thus acquire solution skills. More importantly to obtain, through solving actual problems, the feel for the theoretical underpinnings.
I develop a rather formal course in Mathematical programming, in which the basic philosophy is that you need method to be sure that you are correct. Thus given a problem they must analyze it form a theoretical viewpoint and discover what properties the solution or solutions is likely to have. Then it is a blessing to have NEOS to check that their theoretical knowledge was used to good purpose. Thus I find the NEOS project a very suitable and extremely efficient laboratory for practical optimization from a viewpoint of confirming and analyzing the robustness of the theoretical derivation by good lab work. The idea of laboratory diaries, which was suggested by your request, is I think a worthwhile idea and I will pursue in the future.
I am putting up the course as an interactive distance course on the web and the NEOS server is ideal for practicing. The web course which I am developing is initially in Italian and relies on this type of laboratory work, which I can now execute through the NEOS email server. I suppose that I can also allow the students to connect to my machine and use the telnet facilities to submit problems on NEOS. At the moment, if you notice the requests spring from my machine, because they use the Linux systems in the computing lab to telnet and exploit my machine. By the way, this also works perfectly. I will keep you posted on these developments as it is part of my research.
I have, as I said, a number of prototype software which I use for optimization. The programs allow me to estimate and optimise simultaneously and I solve the problems through a recursive programming approach which solves a quadratic subproblem at each iteration, by solving a linear complementarity subproblem, under trust region constraints. I have been developing it for a number of years and, if it is ever ready and sufficiently robust, I will present it to the Neos server so that it can be used by the MP community if they want to. With this routine I have solved innumerable problems, some extremely large, some combinatorial and so on. Again if anyone is interested I will be happy to send details of the publication of the papers.
The NEOS server is very useful to gauge how traditional implementations fare against my developments. This is now what I propose to do as research in a big way on many practical problems and to launch some theses, so I expect to be using Neos very much. Of course I am very interested in all applications and do some Supply Chain optimization, solve combinatorial problems by embedding them in continuous problems, but I think at the moment, the most fun work that I am doing is to use my simultaneous estimation and optimization routines to solve diagnostic and treatment problems in Medicine. This includes Histopathological diagnosis of colon cancer, osteoporosis detection and treatment, diabetes diagnosis and treatment and so on. These are always simultaneous estimation and optimization problems and thus require comparison with other routines, so that we can develop good theory and computational expertise.
I have used NEOS Server in various courses at University of Missouri --Rolla and Bilkent University and encouraged graduate students to supplement their computational work in their thesis research with various resources provided by NEOS. During the coming Spring semester, I will be asking students to use NEOS Server in the following two courses: Engineering Economic Decisions and Design of Production Planning Systems. In addition, I find NEOS Server an excellent example of an Internet tool in decision sciences.
I teach "Modeling and Optimization" in University of Valencia (SPAIN). During the academic course, we use a GAMS software to model and solve business problems. When the number of variables exceeds the student version (50 binary or integer variables), we use the NEOS Server to solve and analyze the result of our models. I think is very interesting the possibility to use this Internet service. In my opinion this service must be continued.
I am using NEOS as a tool for my OR course. The homework is to use MINLP for mixed integer programming problems. All submissions last week are from my students! NEOS is a very good tool for my teaching.
I do appreciate your kindness in allowing me to run a number of MIP tests with your GAMS programs and XPRESS solvers. I am a student of the last year in Engineering & Management at COMILLAS University in Madrid (Spain). The purpose of my project work is to compare the feasibility, efficiency and speed of solutions provided by existing software programs with some genetic algorithms developed specifically for optimisation problems. I hope to be allowed to continue using your facilities.
Thank you very much for being allowed to use your server. I am working on my PhD in industrial ecology. Much of my work is interdisciplinary, as a result of that I work with many different people who uses various types of tools. Some of my work has been on linking LP models and Environmental input output analysis with LCA. Just recently I've been running some MIP energy technology scenarios with endogenous learning. Working with different people requires often access to various tools. Through you NEOS Server I can both run my MP-models and my GAMS models. Last week my solver would not handle the size of the problems I had modeled, and thanks to your server I have been able to complete my work.
I use the NEOS server for academic purposes, as I work in the Department of Structural Engineering, Technical University of Milan, Italy. In my research activities I have encountered some challenging problems of Mathematical Programming. In detail, I am dealing with ultimate limit-state analyses of large dams by means of a non-standard approach ("direct method"); this requires solving problems of linear and non-linear programming. The NEOS server is an extraordinary tool to perform parametric tests on small models, in order to choose (also with the kind help of NEOS operators) the best suited solver. So far I have used CONOPT, MINOS and SNOPT, by way of the GAMS interface, for my non-linear, non-smooth, non-convex (very cumbersome!) problems, achieving very good results.
It was a very good experience working with the NEOS Server. I would highly compliment the stability of the server. In the one year I used the WWW version of the server, it probably crashed twice. I am indeed impressed. I had been using XPRESS-MP MILP solver to obtain power optimal equivalent inputs to logic circuits. I work in the field of Low Power VLSI Design. I formulated large circuits as ILP problems, submitted them through the WWW interface and obtained good results. In the later part of my research, I had to solve a large number of similar problems. So I used the mailing-in option of the server. I had written a shell script to mail my problem formulation as .mod files to the server and waited for the results to arrive back, which I parsed from the inbox input and processed.
On the whole, the XPRESS-MP solver as part of the NEOS Server was indeed a pleasure to work with. A special mention to the tech support behind the NEOS server. I received outstanding support from them.
I have been using MINLP (AMPL version) at NEOS for my graduate class "Discrete Design Optimization." at ME Department in the University of Michigan. The class is offered every Fall semester (Sept -- Dec) and enrolled by 20-30 students. Without NEOS, I would be in big trouble...
I teach a sophomore-junior class required of all civil engineers. The title is Design and Planning of Civil Engineering Systems, and the topic is optimization as an approach to design. The course is heavy on linear programming, with some non-linear optimization as well. We use two optimization engines: that contained in Excel, and Neos. Our students have found NEOS to be quite useful.
We are planning to test a number of problems related to Chemical Engineering Process design and synthesis (which are optimisation problems) for a postgraduate level course. The testing is with a view to incorporate the facilities of the server for the students.