This function returns a pointer to a newly-created instance of a random number generator of type T. For example, the following code creates an instance of the Tausworthe generator,
gsl_rng * r = gsl_rng_alloc (gsl_rng_taus);
If there is insufficient memory to create the generator then the
function returns a null pointer and the error handler is invoked with an
error code of
The generator is automatically initialized with the default seed,
gsl_rng_default_seed. This is zero by default but can be changed
either directly or by using the environment variable
(see Random number environment variables).
The details of the available generator types are described later in this chapter.
This function initializes (or ‘seeds’) the random number generator. If
the generator is seeded with the same value of s on two different
runs, the same stream of random numbers will be generated by successive
calls to the routines below. If different values of s >= 1 are supplied, then the generated streams of random
numbers should be completely different. If the seed s is zero
then the standard seed from the original implementation is used
instead. For example, the original Fortran source code for the
ranlux generator used a seed of 314159265, and so choosing
s equal to zero reproduces this when using
When using multiple seeds with the same generator, choose seed values greater than zero to avoid collisions with the default setting.
Note that the most generators only accept 32-bit seeds, with higher values being reduced modulo 2^32. For generators with smaller ranges the maximum seed value will typically be lower.
This function frees all the memory associated with the generator r.