XL: Problems with SOLVER Functions

• Microsoft Excel for Windows, versions 4.0, 4.0a
• Microsoft Excel for the Macintosh, version 4.0

SUMMARY

Pages 407-413 of the "Function Reference," contain incorrect information about the SOLVER functions. For information about a particular SOLVER function, see the appropriate section below.

MORE INFORMATION

SOLVER.ADD()

• The first paragraph of the second column on page 407 states that the formula "may be a formula (as text) or a reference to a range of cells." This section should also note that if the formula is entered as text and contains any references, the references must be entered using R1C1 notation.
• The first bulleted item in the right column on page 407 states:

        If "relation" is 4, "formula" is ignored, and "cell_ref" must be
        a subset of the By Changing Cells.
  

  This information is incorrect. If "relation" is 4, "formula" is not ignored. You must use either "=integer" or "integer" (including the quotation marks) for "formula."

• The second bulleted item in the right column of page 407 states:

        ...the number of cells in the range must match the number of cell
        in "cell_ref," although the shape of the areas need not be the
        same.
  

  This information is not entirely correct. A many-to-one ratio is acceptable. For example, "A1:A4 <= B1" will work properly.

SOLVER.DELETE()

• The Remarks section on page 408 states that "The 'formula' argument is not used."

  This information is not entirely correct. If there are two or more constraints for which "cell_ref" and "relation" are the same (for example, A1 <= 5 and A1 <= B1), the "formula" argument is not ignored.

SOLVER.LOAD()

• This function does not work when applied to a worksheet unless the worksheet has already had a Solver model saved onto it.
• The first bulleted item in the left column of page 410 states "The last cell optionally contains an array of Solver option values (see SOLVER.OPTIONS)."

   The order of the options is the same as the top-to-bottom order in
   the Solver Options dialog box.

SOLVER.RESET()

The description of the SOLVER.RESET() function states that this function "is performed automatically when you call SOLVER.LOAD." This information is not entirely correct: SOLVER.RESET() does not reset the options, and so previously set options will be used unless the SOLVER.LOAD() model includes new options settings.

SOLVER.SOLVE()

The values and stopping conditions listed on page 413 are incorrect. The correct values and Stopping conditions are:

   Value           Stopping condition
   ---------------------------------------------------

   0               Solver found a solution. All constraints and
                   optimal conditions are satisfied.

   1               Solver has converged to the current solution. All
                   constraints are satisfied.

   2               Solver cannot improve the current solution. All
                   constraints are satisfied.

   3               Stop chosen when the maximum iteration limit was
                   reached.

   4               The Set Cell values do not converge.

   5               Solver could not find a feasible solution.

   6               Solver stopped at user's request.

   7               The conditions for Assume Linear Model are not
                   satisfied.

   8               The problem is too large for Solver to handle.

   9               Solver encountered an error value in a target or
                   constraint cell.

  10               Stop chosen when the maximum time limit was
                   reached.

  11               There is not enough memory available to solve the
                   problem.

  12               Another Microsoft Excel instance is using
                   SOLVER.DLL(). Try again later.

  13               Error in model. Please verify that all cells and
                   constraints are valid.

SOLVER.SOLVE?()

Page 412 of the "Function Reference" suggests that the SOLVER.SOLVE?() form of the SOLVER.SOLVE() function exists. This information is incorrect: there is no such command.

REFERENCES

"Function Reference," pages 407-413