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 interpret*. *If 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.

Greetings,

Thank-you very much for your work creating/maintaining Open Solver. I’ve tried running version 2.6 on a new 64 bit Windows box with Excel 2013 and I receive the following error:

”

OpenSolver2.6 encountered an error:

Path/File access error (at line 747) (at line 1448) (at line 2810)

Source = OpenSolver, ErrNumber=75

”

I’ve tried running it from My Documents as well as the AddInns director. My company has changed its security settings for macros, so I’m afraid it might be causing the problem (even though I enabled them/trusted source). I will download v2.7 from home (can’t do that at work either) and will try to run. Thoughts?

With aprpeciation,

Jason H.

Please do try with 2.7 and/or the 2.8 prerelease versions and let us know how you go. Tracing this error indicates we are having trouble creating the script to run the solver inside your Temp folder. There are changes to how we deal with the Temp folder in version 2.8, so that might help resolve this problem. You should also try rebooting if you haven’t already, this often helps fix file access-related issues (I doubt it will help here but you never know)

Hello,

Is OpenSolver 2.6 able to generate .nl files for Bonmin and Couenne with binary constraints? The solutions I’m getting appear to ignoring the binary constraints. Manually looking at the .nl files, it seems like binary constraints are not being written in.

I will rebuild my model in a new blank spreadsheet to see if it helps.

Thank you for the progress so far!

Bo

This looks like our bug; thanks for reporting it (and for reading the .nl file – not an activity for the faint hearted!). We will look into this further.

AndrewIt is a bit strange because the BONMIN solver using NEOS works fine.

The NOMAD solver is working fine as well.

We have found and fixed the bug; the next release should resolve this. Perhaps in the meantime you can make the variables integer (whiwch works correctly) with upper bounds of 1. Sorry about this bug, but many6 thanks for reporting it. Andrew. PS: The NEOS code works differently.

Thank you Andrew!

OpenSolver is becoming a formidable product with the inclusion of the nonlinear solvers. NL solvers are very useful when verifying the correctness of a linearized NL model.

I also see that the ‘NEOS using COIN-OR CBC’ engine generates .ampl files! (WOW!)

Is there any way to change the AMPL file to run using the other solvers on NEOS? I tried to change the ‘option solver cbc’ to a different solver but NEOS is giving me errors.

Thanks again!

Thanks for the feedback; we have some great students who have the skills to add these new features. We don’t have the user interface that would let you change the solver yourself – but it is clearly something we need to add partly because it is not a big job. Keep an eye out for a new release (but not the next one which is almost set to go). Thanks again, Andrew

Hi again,

OK, carrying in from before, Opensolver has put an item of the menu bar. I can access the main Model form and try to run the solver. Unfortunatey, it comes back with error 1004 in line 3322 “The index into the specified collection is out of bounds”. Not very meaningful.

The model is currently very simple & stripped-down. The Excel built-in Solver, although not giving a properly optimised solution, nevertheless does not throw any error.

I can only assume that this version of OpenSolver is indeed NOT compatible with Excel 2003.

Please advise.

We do not test against Excel 2003, sorry, and have not done so for some time. But, we hoped it still worked in this old version. We’d welcome your help in testing this further… do you know VBA? Andrew

Hi Andrew,

That’s a pity, considering the description I had read about OpenSolver running on Excel 2003.

Anyway, to answer your question, I know a little VBA & if time allows would like to learn some more. If I can help when time allows, let me know how (& with some guidance).

Best regards,

Graham.

Thanks. We will look into your error report, and try to get back to you over the next few weeks. Also, I have updated our front page to make it clear that Excel 2003 support is not guaranteed! Thanks for taking the time to give us your feedback. Andrew

Hi again,

Hold everything!

I’ve just tried loading OpenSolver 2.6 again.

This time, although it popped up the messages I previously told you about, It has now added a OpenSolver item on the menu bar.

I shall try it out & get back to you.

Cheers.

I excitedly downloaded this version to use on my tried & tested Excel 2003.

When loading, a little window popped up saying “File conversion in progress” & another one saying “This file was created in a newer version of Microsoft Excel. . . . originally contained features not recognised by this version of Excel” & then did nothing. No additional menus or add-ins. I tried several times with the same result. Nada.

I conclude that this is not actually compatible with Excel 2003.

A pity!

When did OpenSolver end support for Excel 2003?

Hey There!

I was just wondering how many variables and constraints is this program limited to?

Cheers,

Ashwini

No limit apart from memory and time.