Incorrect Slack Value Returned in Solver Answer Report

ID: Q116390

4.00 4.00a 5.00 5.00c 7.00 7.00a | 4.00 5.00 5.00a WINDOWS kbref

The information in this article applies to:

Microsoft Excel for Windows 95, versions 7.0, 7.0a
Microsoft Excel for Windows, versions 4.0, 4.0a, 5.0, 5.0c
Microsoft Excel for the Macintosh, versions 4.0, 5.0, 5.0a

SYMPTOMS

In Microsoft Excel, when you use the Solver add-in to find a solution, and you add a constraint that consists of one cell value that depends on another cell value, the Slack value that appears in the Constraint table on the Answer report for that cell is incorrect.

CAUSE

The slack value that appears on the Answer report when you use the Solver add-in is the absolute value of the difference between the two parts of a constraint. The left part of the constraint is the constraint cell, while the right part of the constraint is the target value for the constraint cell. When the right part of the constraint is a constant, the reported Slack value is correct. However, when the right part of the constraint can vary during the solving, the Slack value is not calculated using the final value of the right part of the constraint.

The following is an example of a constraint where the second part of the constraint is a constant:

   $A$1 <= 10

The following is an example of a constraint where the second part of the constraint varies during the solving:

   $A$1 <= $A$2

Using the constraint above, if the final value of the constraint cell ($A$1) is 5, and the final value of the target cell ($A$2) is 10, the Slack value for the constraint cell A1 should be 5. However, when you use Solver with a constraint such as this second example, the Slack value for cell $A$1 is incorrect on the Answer report.

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

REFERENCES

For more information about Creating A Report Using Solver, choose the Search button in Help and type:

   Solver results

KBCategory: kbref KBSubcategory:

Additional reference words: 4.00 4.00a 5.00 5.00a 5.00c 7.00 7.00a add-ins

Version           : 4.00 4.00a 5.00 5.00c 7.00 7.00a
Platform          : WINDOWS

Last Reviewed: September 15, 1996