Written by on Friday March 25th 2011 in Friday Tips, The SIMUL8 Brain

Friday’s Tip – Random numbers

To allow you to analyze the effect changes you make have on your simulation model SIMUL8 keeps the random seed number the same for each run by default.

This way you can be sure the effect is a result of the change you have made rather than a change in variability.

However once you have decided on your final scenario and to properly validate your simulation it is useful to change the random seed number to ensure your simulation still behaves as you expect.

The random numbers enable a simulation to include the variability that occurs in real life. Each place where random numbers are used within a simulation uses a separate stream of random numbers.

This enables a change to be made to one aspect of a simulation, without affecting the random occurrences which will happen at other areas.

By default, when the clock is set back to the start of the simulation time, all the random streams are reset to their starting seeds. This means that a second run of the same simulation will produce the same results.

To change the random numbers which are used, select TRIALS> RANDOM SAMPLING from the main menu.

From the random sampling menu simply enter a number to choose a random number set and click OK. Next time you Reset and Run your simulation this random sample will now be used.

There are 30000 sets of random number streams available in SIMUL8, so with that many to choose from validating your simulation is easy!