Applies to:
Evolver 6.x and Up
@RISK Industrial Edition 6.x and Up

OptQuest error with integer adjustable cells

 

OptQuest requires at least two integer values in each integer adjustable cell’s range. If a cell has only one possible integer, either widen the range or use the Genetic algorithm.

 

Details

• 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).

• In 6.x:

  • With integer adjustable cells, the OptQuest optimization engine requires at least two integer variables in the range of permitted values.

• Occurs when one or more integer adjustable cells have a range that allows only a single integer.

Examples of problematic ranges:

• Minimum = 0, Maximum = 0 → only 0 is possible

• Minimum = 0.5, Maximum = 1.5 → only integer 1 is possible

OptQuest cannot optimize a cell that effectively has only one possible value.

 

Solutions

 

Solution 1 – Adjust the integer cell ranges

1. Remove the affected cell(s) from the list of adjustable cells.

2. Widen the range to include at least two integers:

   • 0 to 1 (includes 0 and 1)

   • 0.5 to 2.5 (includes 1 and 2)

3. If working with percentages or decimals, consider using Discrete instead of Integer, with an appropriate step size:

   • e.g., min = 10%, max = 40%, step = 0.01

 

Solution 2 – Use the Genetic algorithm

• The Genetic engine can run with existing cell definitions.

• Cells where min = max are ignored.

• Steps to select Genetic engine:

  1. Click Settings » Engine » Manual

  2. Choose Genetic

The Genetic algorithm may take a different amount of time and may find a different solution than OptQuest.