Feedback

We welcome your comments on OpenSolver.

539 thoughts on “Feedback”

  1. I have stumbled upon a strange behavior with a non-linear model (the Excel file had been already setup by someone else). The COIN-OR CBC didn’t complain that the problem was non-linear and found a solution, clearly sub-optimal.

    The objective function is a sum of product of continuous and binary variables. Is it possible that OpenSolver has been tricked by a particular setup?

    1. We do only quick checks for non-linearity; these checks can miss cases like yours. The user has to ensure the model is linear. Cheers, Andrew

  2. I am using “Microsoft Excel for Office 365 MSO (16.0.11727.20222) 32 bit”. I downloaded “OpenSolver2.9.0_Linearwin.zip” and extracted the files to a directory. I doubled clicked on “OpenSolver.xlam” and Excel opened, but no OpenSolver commands appeared under the ‘Data” tab of the toolbar. Using “file/options/add-ins” there was no indication that OpenSolver had actually loaded.

    Any assistance will be greatly appreciated!

  3. I sincerely appreciate your generosity in making this program freely available. I wanted to alert you to a bug involving named ranges. I added an OpenSolver worksheet to a financial spreadsheet that tracks my stocks and assets and has a few dozen named ranges. When OpenSolver runs, it replaces a lot of named ranges in pre-existing formulas (not OpenSolver related) in the workbook with OpenSolver-related named ranges. Perhaps if I protected those pre-existing formulas this wouldn’t happen.

    1. OpenSolver does not change any formulae. Perhaps Excel is changing how the formulae are being displayed? Could you email us a screenshot, and the text from About OpenSolver giving the Excel version etc, to email hidden; JavaScript is required . Thanks, Andrew

  4. Cool project. I’m using it with an Excel model written in VBA which runs much slower in Excel 2016. This lets me use the NOMAD non-linear solver with the faster Excel 2007 VBA.

  5. How does OpenSolver evaluate derivatives for non-linear problems? Does it use finite-differencing or algorithmic differentiation, like, e.g., CasADi does?

    1. If we parse the formulae then they are differentiated by the solver, eg by using chain rule I think. The Nomad solver does not use derivatives; it uses a grid style search. Andrew

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