Random number generator
CLEM.RandomNumberGenerator
This component provides a series of random numbers between 0 and 1 for use in stochastic processes.
Description
A number of processes in CLEM simulations require random numbers (see Allowing random variability in your simulation). As there may be a number of CLEM and Market components within a single Simulation, this component like the Clock, provides a single location where all resources and activities can access this computer generated list of random numbers.
This functionality was previously specified in the CLEM component but is now required as a separate component below the Simulation branch of the user interface.
Parameters
The following parameters are used to define this component
generator seed
The random number sequence used is calculated by the computer and is based on a seed or value to start the calculations. If the same seed is used between runs, the outcome will be identical as the same sequence of random numbers will be applied. If however, two runs use different seeds the outcome will be different due to different sequences of numbers being used. A way to ensure each run is different, and not having to change the seed each time, is to use the current time the simulation is performed as the seed. We apply another approach in case two runs of the simulation are performed at the same time on a super computer by providing a generated random number as the seed. This is achieved by setting the seed value to 0 (zero) and will ensure a different sequence for every run of the simulation.
Iteration
While this is not a parameter that can be set, it can be used as a factor in an Experiment to force the simulation to be performed a number of times with the only difference between runs being the random number sequence used (Generator seed must be set to 0). This will result in different outcomes of the model based purely on the random sequence and represents the expected spread of outcomes and can be used to investigate the risk of perverse outcomes. The iteration will be reported as a factor value in all experiment output.