“When we sat down to begin scheduling student volunteers for this year’s Annual Meeting, we recognized an opportunity to use OR methods to make the task more manageable. We realized that the problem consisted of scheduling 59 students across eight shifts (two shifts per day, four days), with each student required to work either one or two five-hour shifts (morning or afternoon). Since student volunteers are placed throughout the conference facilities, we decided to schedule students into the 74 “shift-location” combinations rather than simply assign a block of students into each shift.
A Doodle poll was set up to obtain student availability. Each student was asked to indicate five out of the eight shifts during which they were available. The availability data was translated into a cost matrix where the cost was zero if a student was available and a cost of 1,000,000 if a student was unavailable for a certain shift. The objective was to minimize the total cost of the assigned schedule, thereby creating a feasible schedule that did not assign any students to shift(s) for which they were unavailable.
The problem was set up and solved in MS Excel. The tool used was COIN-OR’s Open Solver add-in for MS Excel…”
Want to be part of our OR/Analytics team at the Department of Engineering Science, University of Auckland in NZ? Check out this job posting.
Just came across a great blog on building the best Fantasy Football team using Excel/Solver/OpenSolver by Tallys Yunes.
Read about OpenSolver being used to reduce maintenance costs in “Safety and Reliability of Complex Engineered Systems: ESREL”, 2015, edited by Luca Podofillini, Bruno Sudret, Bozidar Stojadinovic, Enrico Zio, Wolfgang Kröger.
Kenneth Baker is well known for his excellent introductory texts on optimisation modelling using spreadsheets. It is great to see that his latest edition of “Optimization Modeling with Spreadsheets” (ISBN: 978-1-118-93769-3, July 2015) now includes an online appendix on OpenSolver. I look forward to seeing a copy of this new edition when it arrives. Andrew
I am on sabbatical at DTU in Denmark, and just enjoyed meeting Aleksandr from Maersk in Copenhagen who is doing some great work with OpenSolver (and perhaps SolverStudio in the future) to help make better decisions at one of the world’s largest shipping companies. Aleksandr presented some very sophisticated OpenSolver models, and is one of the few users I know of who uses the Quick Solve feature. (Any more of you out there?) Thanks, Aleksandr, for a great talk, and giving us some challenging models to think about as we plan for faster solve times in future releases. Andrew
There’s an interview online at Chandoo.org with Dan Fylstra, the creator of Solver, the add-in which has made such a contribution in bringing optimization to the millions of Excel users.
Building good linear and integer programming models is not easy. However, I have just come across the AIMMS Optimization Modelling book which covers many important modelling ideas. The AMPL book is also a good reference that I can fully recommend. Enjoy. Andrew
We had a report yesterday from a user Daryl that BitDefender was reporting a possible virus infection on his PC that appeared to be connected with OpenSolver. Thanks to great work by Daryl and our programmer Jack, we identified this as a false positive (i.e. an incorrect report of a virus) being triggered by BitDefender’s ‘heuristics’. BitDefender was objecting to some of our VBA code, including one of our comments. (Note that I said comment, not actual code, and so this is definitely a case of BitDefender being overzealous!) We will tweak our next release to better avoid false reports such as these.
Thanks, again, to Daryl for contacting us with his concerns. Much appreciated.
This user feedback helps summarise why we created SolverStudio, our free tool for Excel users that want to build bigger optimisation models:
Couple of months ago you had advised me to solve [my OpenSolver] model (which takes 1.5 hours to even create set up file) in SolverStudio.
I followed your advise and now I would like to share my real life experience about such a big model.
While OpenSolver was solving my large problem in 2-2.5 hours (including setup and solution), SolverStudio GAMS formulation reduced the solution time to 2 minutes. I’d like to take this opportunity to thank everyone who developed such a tool. Also, SolverStudio greatly quickened up NEOS solver use. It was kind of painful to NEOS solver on its own…
I’m very pleased to see that the pioneers who played such a pivotal role in creating COIN-OR and all the great software that makes OpenSolver & SolverStudio possible have been awarded the INFORMS 2014 Impact Prize. Well done to Brenda Dietrich, JP Fasano, John Forrest, Lou Hafer, Brady Hunsaker, Laszlo Ladanyi, Robin Lougee, Ted Ralphs, and Matthew Saltzman for all their hard work over the years. They will receive their award at the INFORMS conference Award Ceremony this Sunday.
Associate Professor Ted Ralphs is organising a COIN-OR workshop:
at the Informs Computing Society (ICS) conference in January:
Ted will be demo’ing both OpenSolver and SolverStudio at this event, and also giving an overview of all the other tools COIN-OR makes available.
Today, our downloads passed the 100,000 mark. Thanks to all the Engineering Science students who have contributed code to OpenSolver over the years, and all the users and beta testers who have helped us iron out the bugs and add more useful features.
Trying to sell optimisation to your colleagues? This IBM video does a good job:
Thanks to Michael Watson for linking to this from his blog.
One of our OpenSolver users recently worked with modelling guru Stu Mitchell to move his model from OpenSolver to SolverStudio. The OpenSolver model originally took 4 hours to solve. After simplifying the spreadsheet, this reduced to 2 hours. Stu created a SolverStudio version that solved the same problem in just 20 seconds. To quote our user: The conversion to SolverStudio has been an excellent improvement.
If you have a complicated spreadsheet, then you may also find that SolverStudio gives much better solve times. Furthermore, the latest SolverStudio release includes ready-to-run models for many common problem formulations, which helps make the conversion even easier. Give it a go, and let us know how you get on.