Solver FAQs - Questions About Upgrading

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Can the new Solver handle the same types of problems as the 1-2-3 Release 5 Solver?
Does the new Solver provide any new capabilities for defining problems?
The 1-2-3 Release 5 Solver had no fixed problem size limits. What about the new Solver?
Will the new Solver be faster or slower than the 1-2-3 Release 5 Solver?
I have Solver models created with 1-2-3 Release 5. Will the new Solver handle them?
I have macros using {solver-define} and {solver-answer}. Will they work with the new Solver?

Can the new Solver handle the same types of problems as the 1-2-3 Release 5 Solver?

Yes. The new Solver handles both linear and nonlinear problems, of a size at least as great as the old Solver in 1-2-3 Release 5. For details on linear and nonlinear problems, see What kinds of models can the Solver handle?

Unlike the old Solver, the new Solver will produce only one "answer," which is the optimal solution. You can see and, if you wish, save intermediate "answers" by selecting the new Solver's Show Iteration Results option.

On problems with well-defined feasible or optimal solutions, the new Solver will normally find the same optimal solution as the old Solver, within the limits of numerical accuracy. On problems with multiple, locally optimal solutions, the new and old Solver may report different solutions. In rare cases, one Solver may find a solution where the other one couldn't find a solution, but this usually indicates a problem with the model.

Does the new Solver provide any new capabilities for defining problems?

Yes. The new Solver also supports integer constraints, which force some or all of the decision variables to be whole numbers at the solution. You can use integer constraints to handle fixed costs and yes/no decisions, and to express some conditions that would otherwise require @IF or @LOOKUP. This opens up a wide range of new problem types, such as facility location, partial loading, contract awards and many scheduling problems.

The 1-2-3 Release 5 Solver had no fixed problem size limits. What about the new Solver?

The new Solver does have fixed problem size limits of 200 decision variables, and 100 constraints for nonlinear problems. For details, see How large can my Solver models be? But these limits are well above the problem size where the old Solver would report "Cannot solve this problem" or "Out of memory", even on large-memory systems. In practice, the new Solver is able to solve problems substantially larger than those handled by the old Solver. If you need to solve problems of more than 200 decision variables, send us email or call us at (702) 831-0300 to check on availability of our Premium and Large-Scale LP Solvers for 1-2-3 97 and 98 (Millenium) Editions.

Will the new Solver be faster or slower than the 1-2-3 Release 5 Solver?

In most cases, the new Solver is much faster than the old 1-2-3 Release 5 Solver. This is especially true for all-linear models when you select the new Solver's Assume Linear Model option, which allows it to use the (faster and more accurate) Simplex linear programming method. There can be situations where the new Solver is slower than the old one, but these cases are rare, and we may be able to show you how to speed up the solution process with some redesign of your model.

I have Solver models created with 1-2-3 Release 5. Will the new Solver handle them?

Yes. The objective (cell to be maximized or minimized) and the decision variables (adjustable cells) are simply cell ranges in both the old and new Solvers. The new Solver has a different way of representing constraints, but it can recognize constraints in the form of logical formulas as used by the old Solver, and convert them into the new form. It does this automatically when it finds logical formulas in the first cell range you enter in the Add Constraint dialog.

I have macros using {solver-define} and {solver-answer}. Will they work with the new Solver?

Yes. The new Solver supports the same macro commands used to control the old Solver in 1-2-3 Release 5, with some minor changes. You can use {SOLVER-DEFINE} to set up your Solver problem, and {SOLVER-ANSWER} to find a solution. {SOLVER-REPORT} can be used to produce reports, though the selection of available reports is different.

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