About OpenSolver

SolverStudio 0.5 Released, now with Cloud-based Optimisation
SolverStudio 0.5 is available, and now brings cloud-based optimisation to Excel. Available as a free download, SolverStudio lets you use Excel to edit, save and solve optimisation models built using modelling languages such as the Python-based PuLP, AMPL, GAMS, GMPL, COOPR/Pyomo and Gurobi’s Python interface. The latest release allows GAMS and AMPL modesl to be solved in the cloud using the excellent free NEOS servers. The SolverStuduio interface is fully Excel-based, with the model being edited and run from Excel and stored inside the Excel file. This approach provides a much better modelling solution for complex optimisation problems. Check out the screen shots to see how it works. SolverStudio is much better and faster for large problems. However, OpenSolver is still a great tool for simpler models, or spreadsheets that must be compatible with the built-in Solver.

OpenSolver uses the COIN-OR CBC optimization engine

COIN-OR Cup Winner: We are pleased to announce that OpenSolver is the winner of the 2011 INFORMS COIN-OR Cup sponsored by IBM. Thanks, COIN-OR, for this honour.

The latest version, OpenSolver 2.1 (6 Sept 2012) is available for download. Check out this post for the improvements made in the 1.8 version, here for the 1.9 fixes, and here for the 2.1 improvements.

Welcome to OpenSolver, the Open Source linear and integer optimizer for Microsoft Excel. OpenSolver is an Excel VBA add-in that extends Excel’s built-in Solver with a more powerful Linear Programming solver. It is developed and maintained by Andrew Mason and students at the Engineering Science department, University of Auckland, NZ. OpenSolver provides the following features:

• OpenSolver uses the excellent, Open Source, COIN-OR CBC optimization engine to quickly solve large Linear and Integer problems.
• Compatible with your existing Solver models, so there is no need to change your spreadsheets
• No artificial limits on the size of problem you can solve
• OpenSolver is free, open source software.
• Note that OpenSolver does not solve non-linear optimization problems, so your Solver model needs to have “Assume Linear Model” turned on.

As well as providing a replacement optimization engine, OpenSolver offers:

• A built-in model visualizer that highlights your model’s decision variables, objective and constraints directly on your spreadsheet
• A fast QuickSolve mode that makes it much faster to re-solve your model after making changes
• An algorithm to build and update the model only using information present on the sheet
• A modelling tool that we think improves on the built-in Solver window

OpenSolver has been developed for Excel 2003, Excel 2007 and Excel 2010 (including the 64bit version) running on Windows.

You can download OpenSolver.zip (which is hosted on our Open Solver Source Forge site).  Version details (and dates of updates) are shown on the blog page.

OpenSolver is being developed by Andrew Mason in the Department of Engineering Science at the University of Auckland, and Iain Dunning. Kat Gilbert also made valuable contributions to the code while working as a summer student. Development of OpenSolver was made easier by the excellent Excel Name Manager which displays all the worksheet names used by Solver to store an optimization model.

OpenSolver is released as open source code under the GPL. OpenSolver uses the open source COIN-OR CBC optimization engine, the source code of which is available under the Common Public License (CPL). The CBC code has been written primarily by John J. Forrest, and is maintained by Ted Ralphs.

To build its optimization model, OpenSolver iterates through all the decision variables making small changes to each one while recording how the objective function cell and the constraint cells change. This allows the coefficients in the associated equations to be determined. Note that this assumes your model is linear; OpenSolver does some checks of this, but cannot catch every case.

The Excel Solver is a product developed by Frontline Systems for Microsoft. OpenSolver has no affiliation with, nor is recommend by, Microsoft or Frontline Systems. All trademark terms are the property of their respective owners.