Struct rgsl::types::rng::Rng

pub struct Rng { /* fields omitted */ }

Methods

impl Rng

fn new(T: &RngType) -> Option<Rng>

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,

let r = Rng::new(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 GSL_ENOMEM.

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 GSL_RNG_SEED (see Random number environment variables).

fn set(&mut self, s: usize)

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 gsl_rng_ranlux.

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.

fn get(&mut self) -> usize

This function returns a random integer from the generator r. The minimum and maximum values depend on the algorithm used, but all integers in the range [min,max] are equally likely. The values of min and max can be determined using the auxiliary functions gsl_rng_max (r) and gsl_rng_min (r).

fn uniform(&mut self) -> f64

This function returns a double precision floating point number uniformly distributed in the range [0,1). The range includes 0.0 but excludes 1.0. The value is typically obtained by dividing the result of gsl_rng_get(r) by gsl_rng_max(r) + 1.0 in double precision. Some generators compute this ratio internally so that they can provide floating point numbers with more than 32 bits of randomness (the maximum number of bits that can be portably represented in a single unsigned long int).

fn uniform_pos(&mut self) -> f64

This function returns a positive double precision floating point number uniformly distributed in the range (0,1), excluding both 0.0 and 1.0. The number is obtained by sampling the generator with the algorithm of gsl_rng_uniform until a non-zero value is obtained. You can use this function if you need to avoid a singularity at 0.0.

fn uniform_int(&mut self, n: usize) -> usize

This function returns a random integer from 0 to n-1 inclusive by scaling down and/or discarding samples from the generator r. All integers in the range [0,n-1] are produced with equal probability. For generators with a non-zero minimum value an offset is applied so that zero is returned with the correct probability.

Note that this function is designed for sampling from ranges smaller than the range of the underlying generator. The parameter n must be less than or equal to the range of the generator r. If n is larger than the range of the generator then the function calls the error handler with an error code of GSL_EINVAL and returns zero.

In particular, this function is not intended for generating the full range of unsigned integer values [0,2^32-1]. Instead choose a generator with the maximal integer range and zero minimum value, such as gsl_rng_ranlxd1, gsl_rng_mt19937 or gsl_rng_taus, and sample it directly using gsl_rng_get. The range of each generator can be found using the auxiliary functions described in the next section.

fn get_name(&self) -> String

This function returns a pointer to the name of the generator. For example,

println!("r is a '{}' generator", r.get_name());

would print something like "r is a 'taus' generator".

fn max(&self) -> usize

This function returns the largest value that the get function can return.

fn min(&self) -> usize

This function returns the smallest value that gsl_rng_get can return. Usually this value is zero. There are some generators with algorithms that cannot return zero, and for these generators the minimum value is 1.

fn state<'r, T>(&self) -> &'r mut T

This function returns a pointer to the state of generator r. You can use this information to access the state directly. For example, the following code will write the state of a generator to a stream,

void * state = gsl_rng_state (r);
size_t n = gsl_rng_size (r);
fwrite (state, n, 1, stream);

fn copy(&self, other: &mut Rng) -> Value

This function copies the random number generator src into the pre-existing generator dest, making dest into an exact copy of src. The two generators must be of the same type.

fn size(&self) -> usize

This function returns the size of the state of generator r. You can use this information to access the state directly. For example, the following code will write the state of a generator to a stream,

void * state = gsl_rng_state (r);
size_t n = gsl_rng_size (r);
fwrite (state, n, 1, stream);

fn default_seed() -> usize

Equivalent to DefaultRngSeed

Trait Implementations

impl Clone for Rng

fn clone(&self) -> Rng

This function returns a pointer to a newly created generator which is an exact copy of the generator r.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Drop for Rng

fn drop(&mut self)

A method called when the value goes out of scope.