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

Using a Fixed Initial Seed in RISKOptimizer

Using a Fixed Initial Seed

Yes, you can set a fixed initial seed in Simulation Settings on the Sampling tab. This ensures that simulations are repeatable and that results are consistent each time you run RISKOptimizer.

Guidance for Multiple Simulations

In @RISK, go to Simulation Settings » Sampling » Multiple Simulations.

• By default, the option is All Use Same Seed, and this is recommended.

Benefits of using All Use Same Seed:

• Makes it easier to interpret the optimization log.

• Example: if adjustable cells B4 and B5 are used, you may see identical simulation results for (B4=1, B5=1), (B4=1, B5=2), and (B4=1, B5=3), but different results when B4 changes.

  • This indicates that B5 may have little effect on the output.

• Helps the optimization algorithm identify which adjustable cells significantly impact results and focus computation on the most relevant variables.

With Use Different Seeds, simulation results are almost never identical, making it harder to interpret the influence of individual adjustable cells.

Special Note for the Genetic Algorithm

When using the Genetic Algorithm (GA), either because it was selected manually or automatically by RISKOptimizer, setting All Use Same Seed also improves convergence. The GA may backtrack and reuse the same set of adjustable cells. If different seeds are used, identical inputs may produce different outputs, which can slow down GA convergence.