What’sBest!® 9.0 makes available to your Microsoft® Excel® spreadsheet program a highly developed solver capable of performing linear, integer, quadratic, and nonlinear optimization on the most difficult of problems. What’sBest!® gives you access to this solver from within Excel®, and may either be run directly or called from within Visual Basic®.
The earliest version of What’sBest!® became available in 1984 for VisiCalc®, and What’sBest!® has been under continuous development since then. Models have been built for What’sBest!® that solve problems in virtually every field of professional endeavor.
What’sBest!® 9.0 includes major solver enhancements to increase speed and reliability on broad classes of linear, integer, quadratic and general nonlinear models. Other significant enhancements include an improved global solver, an updated presolver and greater user control over the solution process.

Improved Simplex Method

The simplex method has been extended to include:
- Improvements in the dual simplex method that is used to reoptimize at each branch in the branch-and-bound tree. Thus, more branches can be processed per second in the search tree.
- Better handling of numerically difficult linear and integer programs.

Global Solver

Additional global solver parameters have been added to increase performance on models with multiple extreme points. The new discrete space constraint propagation and convex cut generation improve solving nonlinear models and nonlinear problems with integer variables or non-smooth functions. Also, the multi-reformulation mostly lifts bounding performance and enhances tractability through efficient cut generation strategies.

Improved mixed integer solver

The following improvements have been added to the mixed integer solver:
- Major improvements in the heuristics for finding good solutions quickly to integer programs.
- More general branching methods in branch-and-bound that can significantly reduce the time required to prove the optimality of a solution.

Adaptation to Excel® version 2007

The solver module has been redesigned to support up-to-date platforms and operating systems (Windows® XP with Excel® 2003 or Excel® 2007). What’sBest!® can run models saved with the new workbook format ".XLSX" or ".XLSM", but keeping the maximum size of 256 columns and 65536 rows.

Users’ Defined Function Support

This feature allows the user to build models using not only Microsoft® Excel® built-in functions, but also users’ defined functions. The users’ defined functions can be VBA macros, add-in file .XLA, macros calling a user add-in file .XLA, .XLAM, or a library file .XLL.

String Support

This feature allows you to build models using strings as arguments, e.g., in functions such as
IF( ), VLOOKUP( ), and SUMIF( ).