Resolver is an Excel add-in that performs data reconciliation using a high performance, accurate, and robust algorithm optimized for the data reconciliation problem. It uses the same problem setup as the Solver Excel-add-in. In fact the problems are interchangeable. You can setup and solve a problem in Resolver and then use the same setup and problem definition to try and solve it with Solver, just in case you want verification of the results! Resolver is not limited to trivial problems: it has been tested with hundreds of variables, and hundreds of constraints, both linear and nonlinear.
Resolver came about as a result of trying to use Solver to solve process data reconciliation problems, as reported in Is Excel Solver suitable for Production Data Reconciliation?. As noted, Excel has a lot of advantages for setting up process data reconciliation problems, and is widely used for operational and production accounting. Along with some advantages, some issues were revealed which have been overcome with Resolver.Resolver uses a reconciliation model defined via constraint equations expressed as Excel cell formula in the same way as Solver.
The data reconciliation problem is defined in a very similar way to Excel Solver. In fact the model definitions are interchangeable, although Resolver can only solve for the Gaussian objective function, and Solver cannot produce the reconciliation diagnostics.
Resolving will write the results back into the variable cells, and also produces a report to help diagnose the reconciliation problems. This produces the well established gross, constraint, and measurement error diagnostics.