06 Nov

COIN-OR Pioneers win INFORMS Impact Prize

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.

29 Aug

SolverStudio 0.6.03 (20140829) released

SolverStudio 0.6.03 (20140829) has now been released, and is the recommended download. This fixes the issues reported by users in the experimental SolverStudio 0.6.0 (2014.04.07) and includes minor improvements including better searching for GAMS/AMPL/Gurobi installations, a new version of GLPK/GMPL, a fix that caused problems for non-English users, and a change that removes a Python error being reported. All feedback welcome. Andrew

28 Aug

SolverStudio allocates 570 Engineers

Two of my students, Michael and Oscar, have developed a SolverStudio model for allocating students into student groups. This model is now being used successfully by one of our large professional development courses to manage a classs of 570+ students. The model forms student groups that are balanced in factors such as engineering discipline, gender, and grade point average. This tool also creates nice PDF outputs, thanks to Python’s powerful libraries. You can find their model on Github.

This is a great example of how a model can be quickly developed and implemented without requiring the end user to learn new skills beyond their existing Excel expertise.

Well done, Oscar and Michael, for taking the initiative to develop, test and implement this.


30 Jun

Clearing Shrinking Ranges

We have just been working on an implementation in which our data items are defined by named ranges that use formulae, so they expand as the data set expands. When they shrink, they leave old data behind on the sheet. To clear this old data, you can use code such as:

xlDown = -4121
# print ActiveSheet.Range(ActiveSheet.Range(“test”),ActiveSheet.Range(“test”).End(xlDown)).Address()

11 Jun

SolverStudio Speedup: 2 hours to 20 seconds

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. But, Stu then 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 than a traditional OpenSolver model. Furthermore, the latest SolverStudio release includes ready-to-run models for many common problem formulations, which helps make using SolverStudio even easier. Give it a go, and let us know how you get on.


16 Apr

Bug reporting for CBC, NEOS, Pyomo

It was an interesting experience testing the latest SolverStudio 0.6.0 release. We discovered several independent bugs in CBC 2.8.8 on Windows which means (1) CBC often finds incorrect solutions when used with AMPL, and (2) it reports the wrong objective function value for these; thanks for Victor Zverovich from AMPL and John Forrest from COIN-OR for working with us to fix these ready for the next CBC release. We also found a bug in Pyomo’s output formatting that John Sirola is working on; we suggest for now you do not put comma’s in the values of indices. Finally, we think the output from NEOS has changed the way it is formatted; we have put in a work around while Ziliang Guo from NEOS looks into this. Who would have thought it would be such a busy week! Andrew

16 Apr

SolverStudio 0.6.0 (2014.04.07) – Excel 2013 support, plus more

SolverStudio 0.6.0 (2014.04.07) has been released, with numerous bug fixes and improvements. This experimental beta includes:
  • beta Excel 2013 compatibility – please let us know how it works for you
  • fixes for NEOS changes,
  • the latest CBC and IPOPT solvers,
  • the latest GMPL,
  • much easier CPython support for scripting Excel,
  • a new Scintilla editor with syntax highlighting,
  • and numerous small improvements,

We have also include a new example file, “Common Formulations.xlsx”, that makes it easy to solve common optimisation models, including transportation, transshipment, assignment and knapsack model. You can also enter and solve a standard (inter) linear program, and should be able to solve more quickly than you can using OpenSolver. None of these require any understanding of SolverStudio models, and so are suitable for a wider range of users.

The new editor (and thus SolverStudio) needs the full .Net Framework 4.0, and not the .NET Framework 4 Client Profile as was used previously. This will be installed if required, and may require administrator privileges.
All feedback most welcome.