Troubleshoot Solver

ShowSolver stops before a solution is found.

Solver might stop before reaching a solution for any of the following reasons:

  • You interrupted the solution process.
  • You selected Show Iteration Results in the Solver Options dialog box before you clicked Solve.
  • You clicked Stop while stepping through iterations or when the maximum time or number of iterations was reached.
  • You selected the Assume Linear Model check box in the Solver Options dialog box, but the problem is nonlinear.
  • The value in the Set Target Cell you specified in the Solver Parameters dialog box is increasing or decreasing without limit.
  • You need to allow Solver more time to find a solution. Adjust the Max Time or Iterations setting in the Solver Options dialog box.
  • For problems with integer constraints, you need to decrease the Tolerance setting in the Solver Options dialog box so that Solver can find a better integer solution.
  • For nonlinear problems, you need to decrease the Convergence setting in the Solver Options dialog box so that Solver can keep searching for a solution when the target cell value is changing slowly.
  • You need to select the Use Automatic Scaling check box in the Solver Options dialog box because some input values are several orders of magnitude apart, or input and output values differ by several orders of magnitude.

When Solver stops, a completion message appears in the Solver Results dialog box. Click Keep Solver Solution or Restore Original Values, make the changes you want, and then try again.

ShowThe adjustable cells and constraint or target cells differ in magnitude.

When the typical values of the adjustable cells and the constraint cells or target cells differ from each other by more than a few orders of magnitude, select the Use Automatic Scaling check box in the Solver Options dialog box. For nonlinear problems, before you click Solve in the Solver Parameters dialog box, make sure that the initial values of the adjustable cells are the same order of magnitude as you expect for the final values.

ShowI didn't get the solution I expected.

For nonlinear problems, it can be helpful to try different starting values for the adjustable cells, especially if Solver has found a solution that is significantly different from what you expected. You can also reduce the solution time by setting the adjustable cells to values that you suspect are close to optimal.

For linear models (that is, when the Assume Linear Model check box on the Solver Options dialog box is selected), the initial values of the adjustable cells don't affect the final values or the solution time.

ShowThe solution found by Solver was different from the previous result.

Solver displays the following message, "Solver has converged to the current solution. All constraints are satisfied." The relative change in the target cell is less than the Convergence setting in the Solver Options dialog box for the last five trial solutions. If you provide a smaller value for the Convergence setting, Solver could try for a better solution but would take more solution time.

ShowSolver cannot reach an optimal solution.

The following lists completion messages displayed by the Solver.

ShowSolver cannot improve the current solution. All constraints are satisfied.

Only an approximate solution has been found, but the iterative process cannot find a better set of values than those displayed. Either further accuracy is not achievable, or the precision setting is too low. Try changing the precision setting in the Solver Options dialog box to a larger number, and then run the problem again.

ShowStop chosen when the maximum time limit was reached.

The maximum amount of time has elapsed without finding a satisfactory solution. To save the values found so far and also save future recalculation time, click Keep Solver Solution or Save Scenario.

ShowStop chosen when the maximum iteration limit was reached.

The maximum number of iterations has been reached without finding a satisfactory solution. Increasing the number of iterations might help, but you should examine the final values for insights into the problem. To save the values found so far and also save future recalculation time, click Keep Solver Solution or Save Scenario.

ShowThe Set Target Cell values do not converge.

The value for the target cell is increasing (or decreasing) without bound, even though all constraints are satisfied. You might have omitted one or more constraints in setting up the problem. Check the current worksheet values to see how the solution is diverging, check the constraints, and then run the problem again.

ShowSolver could not find a feasible solution.

Solver could not find a trial solution that satisfies all constraints within the precision setting. It is likely that the constraints are inconsistent. Examine the worksheet for a possible mistake in the constraint formulas or in the choice of constraints.

ShowSolver stopped at user's request.

You clicked Stop in the Show Trial Solution dialog box, either after interrupting the solution process or when stepping through trial solutions.

ShowThe conditions for Assume Linear Model are not satisfied.

You selected the Assume linear model check box, but the final calculations in Solver yield values that do not agree with the linear model. The solution is not valid for the actual worksheet formulas. To check whether the problem is nonlinear, select the Use automatic scaling check box, and run the problem again. If you see this message again, clear the Assume linear model check box, and then run the problem again.

ShowSolver encountered an error value in a target or constraint cell.

One or more formulas yielded an error value on the latest calculation. Find the target or constraint cell that contains the error, and change its formula to yield an appropriate numeric value.

You typed an invalid name or formula in the Add Constraint or Change Constraint dialog box, or you typed "integer" or "binary" in the Constraint box. To constrain a value to an integer, click Int in the list of comparison operators. To set a binary constraint, click Bin.

ShowThere is not enough memory available to solve the problem.

Microsoft Excel couldn't allocate the memory needed by Solver. Close some files or programs and try again.

ShowAnother Microsoft Excel instance is using SOLVER.DLL.

More than one Microsoft Excel session is running, and one session is already using Solver.dll. Solver.dll can be used in only one session at a time.

 
 
Applies to:
Excel 2003