OpenSolver 2.6 (8 Oct 2014) with Mac OSX support

We are happy to announce that OpenSolver 2.6 has been released.

This is a major release that supports Office 2011 for Mac OSX for the first time! Nearly all of the features of the Windows version are working on Mac, the only notable exception is the non-linear NOMAD solver, which is not supported on the Mac version at this stage. However, all of the other non-linear solvers are available as normal.

This brings us to the other main addition in this release which is the ability to use the COIN-OR non-linear solvers locally. The Bonmin and Couenne solvers were previously only available on NEOS as cloud-based solvers, but they can now be used on your machine locally (both Windows and Mac), which should offer more convenience. This feature is very experimental, as these solvers rely on us converting the Excel model into another model format and we currently only support doing this for a subset of the functions in Excel (most common functions are working). These solvers will fail if your spreadsheet uses functions OpenSolver cannot interpretIf you get a message about an unsupported function, please let us know so we can look at adding it in. These solvers are included in the ‘Advanced’ release, more on that next.

The last main difference in this release is the release format. Instead of offering a single download, we are offering separate downloads for Windows and Mac. This is so Windows users don’t have to download the solvers for Mac, and vice-versa. We are also introducing ‘Linear’ and ‘Advanced’ downloads. The Linear download only contains the linear CBC solver, whereas the experimental Advanced download comes with the non-linear solvers Bonmin, Couenne, and NOMAD. Both releases can use the NEOS solvers, and can use Gurobi if installed on the machine. If you aren’t sure, the default download is the Linear version for your computer (either Windows or Mac as appropriate).

Other changes include:

  • NEOS solvers now write AMPL files to disk before sending the model to NEOS. These can be used to run the model locally using AMPL if you have it installed
  • Resolve bugs introduced by system-locale settings
  • Upgrade NOMAD to v3.6.2
  • Bugfixes for non-linear NOMAD solver
  • Bugfixes for NEOS solvers
  • Various other bugfixes

You can see the releases here. There are a lot of changes in this release, especially since it is the first Mac release, and we are looking for any feedback you have, as well as any problems you might run into while using it.

OpenSolver 2.5.3 alpha (2 Jul 2014)

In this release we are adding support for the NOMAD non-linear solver in 64-bit Office. Differences between the 32 and 64-bit versions of Office previously caused NOMAD to crash in 64-bit Office, but these issues have been identified and resolved now.

For anyone that might run into a similar problem in the future, the problem was our use of Application.Run to access the NOMAD DLL:

Application.Run("NomadMain", SolveRelaxation)

When Application.Run was used like this on 64-bit Office, any C API calls from the DLL back into Excel would fail. Instead, the function must be called directly and everything then works fine:


You can get it here. Let us know how NOMAD goes in 64-bit Office, and we welcome any other feedback too!

OpenSolver 2.5.1 alpha (25 Jun 2014)

Today we are releasing OpenSolver 2.5.1 alpha, which builds on the 2.5 alpha release from last week.

The main addition in this release is the option to use the non-linear solvers Couenne and Bonmin through the cloud-based NEOS servers.

We have also included a 64-bit version of CBC that is used automatically on 64-bit systems.

There are also stability fixes for the non-linear NOMAD solver that was included in the 2.5 release, and other bug fixes.

You can download it here. Like 2.5, this is an experimental alpha release, and we are looking for feedback on the new features, as well as any problems you might run into while using them.

OpenSolver 2.5 alpha (20 Jun 2014)

We have just released OpenSolver 2.5 alpha, which has a number of fixes and improvements. It also has some new experimental features.

You now have the ability to select from number of different solvers:

  • CBC (included and upgraded to version 2.8.8 in this release)
  • Gurobi LP/IP solver (if this is installed on your machine)
  • NOMAD non-linear solver (included, supported in 32-bit Office only for now)
  • Solvers on the cloud-based NEOS servers – CBC (linear) is supported now, and we hope to offer Couenne and Bonmin (both non-linear) in a future release.

This release also adds reporting of dual variables and sensitivity analysis, and as well as many small bug fixes and feature enhancements. Many thanks to students Matt, Kris, and Jack for their work on these enhancements.

You can download it here. All feedback is welcome, particularly regarding the new experimental features.


OpenSolver 2.1 (6 Sept 2012)

OpenSolver 2.1 is now released, and has a number of fixes and improvements. These include a newer version of the optimiser CBC, a bug fix for handling multiple cell blocks as decision cells on non-English systems, more robust non-linearity checking, and the ability to turn off this non-linearity checking if you know your model is linear. We now also display ≥ instead of > in our on-sheet constraints. All feedback is welcome.

OpenSolver 1.9 (5 Dec 2011)

Fixed some display issues in the model dialog to give more compact displays, and force formulae RHS to be in absolute terms
Fixed a bug that saw models being wrongly built and then reported as non-linear (incorrectly) for some complex models if Excel calculation mode was set to manual.
Fixed passing of multiple parameters to CBC if the user defines a parameter table on the sheet; previously only the last parameter was passed.
Deleted the DLL’s downloaded in the .zip file which don’t seem to be needed now that we statically link everything in CBC.

OpenSolver 1.8 (5 Dec 2011)

Version 1.8 fixes a problem that prevented OpenSolver 1.7 loading on 64 bit systems, and improves handling of models that have decision variables and constraints on multiple sheets. Note that Excel does not allow ranges to contain arbitrary cells from many sheets, and so all the decision variables must be on the same sheet.

OpenSolver 1.7 (11 November 2011)

OpenSolver 1.7 has been released. (OpenSolver 1.6 was an internal release only.) Changes include:

Version 1.7 beta
Added controls in the About box to allow easy installation and uninstallation
Added code to interact nicely with the forthcoming OpenSolver Studio
Improved OpenSolver for use from VBA:
– Build and Solve operations now throw errors (instead of popping up dialogs), allowing dialog-free usage from VBA
– Return codes are better handled (and Solver compatible)
– A new optional parameter has been added to RunOpenSolver to avoid dialogs even if infeasible/unbounded solutions are generated

Version 1.6 beta
Fixed display and editting of an objective target value in the Model dialog.
Modified the Open Last Model in CBC functionality so that it passes any Solver options and any CBC solve parameters to CBC if they are available in any current worksheet
Fixed a minor issue in Model dialog where a RHS could be entered for a new constraint if the user had previously had a Bin or Int constraint selected
Fixed a redim bug in the quick non-linearity checker for models with no constraints (which can happen if there is only a target objective value)
Added “Show optimisation progress while solving”  (being Solver’s “Show Iteration Results”) to the OpenSolver options dialog
Improved operation of Options dialog, including proper sycnronisation of values when opened from the Model dialog
Better handling of the Excel 2010 “Simplex engine” option as used in parallel with “Assume linear model”
Fixed an error in the full non-linearity checker
Added output of dual prices onto the sheet; this is set using the Model dialog
Rearranged Model dialog to better fit new Duals option, and better use space around constraint listing
Better handling of the Excel solver options – OpenSolver now sets all these to sensible defaults
Better handling of users entering formulae in the Model dialog for a constraint RHS in terms of non-English localisation issues, but this still needs work
Fixed a size limitation in Quick Solve, and converted Quick Solve to sparse matrix handling for better memory usage.

OpenSolver 1.5 (9 August 2011)

We are pleased to announce the release of OpenSolver 1.5!

This is a bug-fix release:

  • Re-compiled CBC so that it does not have any external dependencies.
  • Fixed an error with cells formatted as currency or date.
  • Fixed some localisation-related issues with tolerance/ratio gap.

Thank you for submitting bug reports – they are very handy in solving problems. With so many different system configurations out there, it can be tricky to test even a fraction!

OpenSolver 1.4 (31 July 2011)

We are pleased to announce the release of OpenSolver 1.4!

For a full changelog, please see the document in the download.

  • Fixed 2003 menus – version 1.3 had some issues remaining.
  • Fixed some issues with and streamlined AutoModel
  • Fixed a ref-edit related focus bug in Model tool that was causing some strange behaviour.
  • Added partial locale support to Model. Entering number like 180,2 will work, but will display as 180.2
  • Added an Options window, available under Model in menu, and from a button on the Model form.
  • Added error catching in int/bin constraints on non-decision variable cells.
  • Updated CBC to version 2.7
  • Added custom icons for toolbar!

As always, please report any bugs via email or as comments.

OpenSolver 1.3 beta (7 July 2011)

We are pleased to announce the release of OpenSolver 1.3 beta!

Big features in this release are:

  • Excel 2003 menu support, thanks to Paul at Eclipse Engineering. Eclipse Engineering provide high-end CFD and FEA analysis along with a host of highly specialized CAE-based automation and integration solutions.
  • Support for 64-bit Excel 2010 has been added.
  • Removed last dependence on the built-in Solver: you can now build a model in the OpenSolver Model window!
A screenshot of the new Model tool
The new Model tool in OpenSolver 1.3

Bug reports are very welcome.

OpenSolver 1.2 is now the official stable version of OpenSolver.

OpenSolver 1.1beta released (4 March 2011)

OpenSolver 1.1beta is now available for download. OpenSolver can now run in Excel 2010 as well as 2007, and solves much larger problems and does so more quickly. (We tested on a problem with 70,000 variables and 70,000 constraints sent in by a user!) There are lots of little bug fixes and big improvements, including an AutoModel feature that provides an optional alternative to the Solver dialog; many thanks to my student Iain Dunning for coding this up. We now also check that the model is linear, and highlight any problems. Thanks to Kathleen Gilbert for working over her holidays to make these improvements. You can download the beta here. We look forward to your feedback.