Random number generators

For the simulation of random fields, gstat can use one of several random number generators (RNG). The default generator depends on the platform on which gstat was compiled:

• when the GNU Scientific Library (GSL) was present, the default rng is mt19937 in this library
• else, when drand48 is present on the platform, this random number generator is used by default
• else, Marsaglia's random number generator is used.

The default RNG can be controlled with the command line option -r (section 5.2), try

gstat -r -1.

for an overview of available RNG's.

The GSL provides 26 different generators, and the one used is controlled by setting the environment variable GSL_RNG_TYPE to one of the following values: ranlux389 ranlux cmrg mrg mt19937 tt800 taus ran0 ran1 ran2 ran3 ranf rand48 ranmar zuf slatec r250 random minstd uni uni32 vax transputer rand random8 randu. See the GSL documentation for details.

The seed of the RNG can be set by the variable seed. Default, the seed is read from the CPU clock (using microseconds, when the function gettimeofday is present, or else seconds). For the GSL, the environment variable GSL_RNG_SEED may be used to override the seed in gstat (set or default).