Random numbers

The SIGSPEC simulator is capable of modelling three different types of random processes:

• serially correlated noise (keyword sim:serial, p.),
• temporally correlated noise (keyword sim:temporial, p.),
• random steps (keyword sim:rndsteps, p..

The random number generator employed for these models may be initialised in two different ways.

1. The user may pass an integer value to the program. This value has to be written into a file <project>.rnd.
2. If the file <project>.rnd is not present, the simulator initialises the random number generator using the system time.

The last integer value in the sequence of random numbers is written to a file <project>/<project>.rnd. This allows to embed SIGSPEC into an external loop for numerical simulations. If the output file <project>/<project>.rnd is moved to <project>.rnd externally between consecutive SIGSPEC runs, the program may used iteratively without breaking the random number sequence.

Example. The simulator is employed in the sample projects sim-serial, sim-temporal and sim-rndsteps. To initialise the random number generator, a file sim-serial.rnd, sim-temporal.rnd and sim-rndsteps.rnd, respectively, is used to make the output reproducible.

Consequently, the user has three options to explore the these samples.

1. If the samples are processed as they are, SIGSPEC reproduces the given output exactly.
2. If the .rnd file in the input directory is removed by the user, SIGSPEC produces a new set of random numbers. The random number generator is initialised employing the system time.
3. If the content of the .rnd file in the input directory is modified by the user, SIGSPEC produces a new set of random numbers. The random number generator is initialised employing the new number in the .rnd file.