HomeTroubleshootingEvolver and RISKOptimizer"With integer adjustable cells, the OptQuest optimization engine requires ..."

10.6. "With integer adjustable cells, the OptQuest optimization engine requires ..."

Applies to:
Evolver 6.x/7.x
@RISK Industrial Edition 6.x/7.x

When I click the start button for my optimization, this message pops up in 7.x:

With integer adjustable cells, the OptQuest optimization engine requires at least two integer values within the range of minimum to maximum (inclusive). Either change the adjustable cell definitions or try the Genetic optimization engine.

In 6.x, it's this message:

With integer adjustable cells, the OptQuest optimization engine requires at least two integer variables in the range of permitted values. It may be possible to use the Genetic optimization engine with the current adjustable cell definitions.

What is wrong, and how do I fix it?

The message is trying to tell you that some or all of your adjustable cells are constrained to be integers, and one or more of those integer adjustable cells have minimum and maximum too close together. For example, if minimum is 0 and maximum is 0, the only possible value that meets constraints is 0.  Similarly, if minimum is 0.5 and maximum is 1.5, the only possible integer value that meets constraints is 1.  But a cell with only one possible value can't really be called an "adjustable" cell, and OptQuest won't allow this. You can apply either of two solutions.

Solution 1:
For the cells where minimum and maximum are too close together, you have three ways to fix the problem:

• Remove the affected cell(s) from the list of adjustable cells.
• Change the definition so that the range [minimum to maximum] includes at least two integer values.  Examples: 0 to 1 (includes integers 0 and 1), or 0.5 to 2.5 (includes integers 1 and 2).
• If your min and max are percentages or other decimals, use Discrete with some smaller increment, rather than Integer. Example: for min = 10%, max = 40%, you might use Discrete with a step size of 0.01.

Solution 2:
The Genetic algorithm will usually run with your existing model definition, ignoring the cells where minimum equals maximum and varying the other adjustable cells. (It may take more or less time than OptQuest and may reach a different solution, depending on your model.) To select the Genetic algorithm in Evolver or Optimizer, click Settings » Engine » Manual and if necessary select Genetic.

Last edited: 2018-07-23