Runtime Tab

The Runtime tab displays Evolver settings that determine the runtime of the optimization. These stopping conditions specify how and when Evolver will stop during an optimization.  Once the optimization is begun using the Start command, Evolver will search for better solutions and running simulations until the selected stopping criteria are met.  Any number of these conditions can be set, or all of them can be disabled.

When multiple conditions are checked, Evolver will stop as soon as any one of the chosen conditions is met. Stopping conditions can be manually overridden at any time by using the Stop button in the Evolver Watcher or Progress windows.

Available options for the analysis runtime include:

• Trials -Analysis stops when the given number of trial solutions have been generated.

• The Trials setting is particularly useful when comparing Evolver’s efficiency across different modeling methods. By changing the way a problem is modeled, or by choosing a different solving method, the efficiency of Evolver's analysis can be increased. Having a model run a specified number of trials will indicate how efficiently Evolver is converging to a solution, regardless of any differences in the number of variables chosen or the power of the computer hardware being used.

  The Optimization Summary worksheet is also useful in comparing results across runs. For more information, see Optimization Summary.

• Time - Stop Evolver from generating scenarios after the given number of hours, minutes, or seconds has elapsed.
• Progress - Stop Evolver from generating scenarios when the improvement in the target cell value is less than the specified amount.
• • Maximum Change - The greatest degree of change that Evolver will recognize as valid and continue analysis. This option can be expressed as a percent or as a static value using the pulldown to the right of the value.
  • Number of Trials - The number of trials over which to check the improvement. The more complex the optimization problem, the larger the number of trials you should specify in this stopping condition.

  • This is the perhaps most popular stopping condition, as it provides an effective way to stop analysis after the improvement rate is slowing and better solutions are likely not possible.

    For example, when trying to maximize the value of the target cell, the values used in the Progress stopping condition could be 20000 trials, and 0.01% change. In this scenario, suppose that after 10,000 trials, the best target cell value found is 2000.  If the Progress option is the only stopping condition selected, when Evolver gets to trial 30,000 (20,000 successive trials), analysis will continue only if Evolver is able to find a target cell value of at least 2000.2 during those last 20000 trials (a 0.01% change to the best value found after 10,000 trials). In other words, if the target cell values have not improved at least 0.01% over the last 20,000 trials, Evolver concludes there is little more improvement to be found, and it stops the search.  

• Formula is True - This stopping condition causes the optimization to stop whenever the entered (or referenced) Excel formula evaluates to TRUE during the optimization.
• Stop on Error - This stopping condition causes the optimization to stop whenever an Error value is encountered for the target cell.