Random Number Generator

Stochastic models require a random seed value for the pseudorandom number generator. In this case model runs cannot be reproduced since the model random number generator is initialized with different values for each model run. Specifying the fixed seed value, you initialize the model random number generator with the same value for each model run, thus the model runs are reproducible.

 To set up random number generator seed
  1. In the Projects view, select the experiment you are currently working with.
  2. Go to the Randomness section of the Properties view.
  3. In the Random number generation group of buttons: 
  4. To set random seed, choose the Random seed (unique experiments) option.
  5. To set fixed seed, choose the Fixed seed (reproducible experiments) option and enter the seed value in the Seed value edit box.

If the model does not receive any external input (either data or user actions), the behavior of the model in two simulations with the same initial seeds is identical. The random number generator is initialized once when the model is created and is not reinitialized between model replications.

 In some rare cases the model may output non-reproducible results even with the option Fixed seed (reproducible experiments) being selected. These situations are described here.