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To download a free Evaluation Version of the XPRESS Solver Engine Version 3.5, click here to sign up (free of charge) for Frontline's Private Web for Solver Users. Then click on Download, scroll to the bottom and follow the link to Download Evaluation Version of XPRESS Solver Engine.
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Frontline Systems is excited to offer the XPRESS Solver Engine Version 3.5 for Microsoft Excel 2000 and Excel 97. The XPRESS Solver Engine is a new, extraordinarily powerful, field-installable Solver Engine that "plugs into" the Premium Solver Platform. Based on the latest version of XPRESS-MP from Dash Associates, it extends the power of the Premium Solver Platform to handle linear programming problems up to a remarkable 200,000 variables and 200,000 constraints. It solves mixed-integer linear (MIP) problems with astonishing speed -- and it supports the new "alldifferent" constraint introduced in the Premium Solver Platform V3.5.
The Premium Solver Platform is 100% upwardly compatible with the standard Excel Solver. It replaces the standard Solver and appears when you select the usual Tools Solver... menu choice. You'll see a familiar Solver Parameters and Solver Options dialog with many new features. Your existing models can be solved with no changes, faster and more easily than before -- with any appropriate Solver engine for the Premium Solver Platform, including the XPRESS Solver Engine! And your VBA code designed to control the standard Solver will work as-is with the Premium Solver Platform.
You'll be able to solve linear programming problems a thousand times larger than the standard Excel Solver -- up to a remarkable 200,000 variables and 200,000 constraints -- with the XPRESS Solver Engine. And you'll be amazed at the lightning-fast solution times you can obtain: Problems with many thousands of variables and constraints often solve in just seconds! You'll typically solve problems hundreds of times faster than the Premium Solver Platform's built-in linear programming Solver.
The XPRESS Solver Engine is lightning-fast on linear programming problems, but its performance on mixed-integer linear programming problems is breathtaking -- many optimization experts consider XPRESS-MP to be the world's best general-purpose mixed-integer optimizer. MIP problems that take prohibitively long -- hours or even days -- to solve, even with the Premium Solver Platform's built-in mixed-integer strategies, will often solve remarkably quickly with the XPRESS Solver Engine -- sometimes in just seconds!
Larger linear programming models often spend most of their time in problem setup, then reach a solution quickly. The XPRESS Solver Engine and the Premium Solver Platform will give you an immediate speedup -- often completing problem setup in half the time. But with a little work in designing your model to use certain common functions (like SUM and SUMPRODUCT), the XPRESS Solver Engine can give you a really awesome speedup -- as much as a hundred times faster!
With the XPRESS Solver Engine, you can choose either an advanced primal Simplex method, a very high performance dual Simplex method, or a state of the art Newton Barrier ("interior point") method to solve linear programming problems. For mixed-integer (MIP) problems, XPRESS uses an advanced Branch & Cut method, which combines Branch & Bound with "cut generation" strategies, that you can easily customize.
The XPRESS Solver Engine takes advantage of sparsity in large LP models, where subsets of the constraints typically depend on only a small subset of the variables. For example, an LP coefficient matrix for a problem with 2,000 variables and 2,000 constraints would take about 32 megabytes for matrix storage using dense storage methods, but if this problem has the sparsity typical of larger models, it would take 1 to 1.5 megabytes using the sparse storage methods in the XPRESS Solver. And the XPRESS Solver Engine uses advanced matrix factorization methods to maintain numerical stability on large problems.
The XPRESS Solver Engine features more than 60 user-controlled options and tolerances. But relax -- since they all have intelligent default values, you won't even have to look at most of them unless you want fine-grained control of solution strategies. The options are organized into "basic" and "advanced" sets that appear in panes in the Solver Options dialog. You can easily select the solution method (primal Simplex, dual Simplex or Newton Barrier), a variety of Branch & Bound and Branch & Cut strategies for mixed-integer problems, time and iteration limits, and the like. For a more complete description of the XPRESS Solver Engine's options and tolerances, click here (TBD).
If you've ever received the message "The conditions for Assume Linear Model are not satisfied," but you couldn't find the problem in your model, the XPRESS Solver Engine V3.5 is for you! It features a Linearity Report, which shows you whether the objective and each constraint is a linear or nonlinear function of the variables. It also summarizes which variables occur linearly, and which occur nonlinearly in the objective and constraints. With this report, you can pinpoint and, if desired, eliminate nonlinear formulas in your models, thereby gaining the extra speed and reliability available with all-linear Solver models.
When the Solver reports that it cannot find a "feasible solution" (one which satisfies all of the constraints), this often means that you’ve made a mistake in defining some constraint, for example by choosing <= when you meant >=. But if you have hundreds of constraints, it can be difficult to pinpoint the source of the problem. The XPRESS Solver Engine V3.5's new Feasibility Report can help! This report eliminates constraints which do not contribute to the infeasibility, and highlights a minimal set of constraints which are conflicting. With the Feasibility Report, you can quickly locate the error or condition that makes the problem infeasible.
In the XPRESS Solver Engine V3.5, all five reports (Answer, Sensitivity, Limits, Linearity and Feasibility) can be optionally, automatically outlined. The outlined groups of variables and constraints correspond directly to the cell ranges you entered in the Solver Parameters dialog. If you have large numbers of variables and constraints, outlining can make it much easier for you to find and display the information you need in the Solver reports.
If you've found it difficult to enter your decision variable cells in the Solver because they are scattered around your worksheet, the XPRESS Solver Engine and the Premium Solver Platform are for you! They offer a variable cell list box entry alternative that allows you to enter an unlimited number of cell ranges. If you're tired of selecting Tools Solver... from the menu bar over and over as you solve various problems, you'll appreciate the "Return to Solver Parameters" check box in the Solver Results dialog, which lets you "stay within the Solver dialogs" until you need to work directly on your spreadsheet. And if your problem includes integer constraints, you can obtain a quick solution of the "relaxation" (temporarily ignoring the integer constraints) without having to delete these constraints and then re-enter them later.
Have you ever wondered about the size of the problem you have defined, and whether it is getting close to the size limits of the Solver? With the XPRESS Solver Engine and the Premium Solver Platform, you can check the size of your problem and the corresponding size limits in the Options dialogs at any time.
Have you ever wondered just how long "Setting Up Problem..." would take? If so, you'll appreciate the new progress reporting in the XPRESS Solver Engine V3.5, which shows an estimated "nn% Done" for both problem setup and generation of the Limits and Feasibility Reports, which can be time-consuming for larger models.
You'll appreciate the comprehensive 67-page User Guide that comes with the XPRESS Solver Engine, and supplements the 150-page User Guide that comes with the Premium Solver Platform. It provides complete information on XPRESS Solver Engine options, the various messages which the XPRESS Solver Engine can return, how to diagnose problems, and how to control the XPRESS Solver Engine from Visual Basic in Excel.
The XPRESS Solver Engine V3.5 is priced at $6,995, including 90 days of knowledgeable technical support and automatic upgrades to new versions. You can order today with a 30-day money-back guarantee. Upgrades are available from Frontline's Large-Scale LP Solver Engine (Standard or Extended versions) to the XPRESS Solver Engine. Discounted prices are available for qualified academic users -- contact Frontline Systems for more information.
If you own another "Solver" product for Microsoft Excel, email or call us for the good news on competitive upgrade pricing! CONTACT US TODAY: Send us email, call us at (775) 831-0300, or send a fax to (775) 831-0314.
