Stdlib.Random
Pseudo-random number generators (PRNG).
With multiple domains, each domain has its own generator that evolves independently of the generators of other domains. When a domain is created, its generator is initialized by splitting the state of the generator associated with the parent domain.
In contrast, all threads within a domain share the same domain-local generator. Independent generators can be created with the Random
.split function and used with the functions from the Random.State
module.
Initialize the domain-local generator, using the argument as a seed. The same seed will always yield the same sequence of numbers.
Same as Random.init
but takes more data as seed.
Initialize the domain-local generator with a random seed chosen in a system-dependent way. If /dev/urandom
is available on the host machine, it is used to provide a highly random initial seed. Otherwise, a less random seed is computed from system parameters (current time, process IDs, domain-local state).
Random.int bound
returns a random integer between 0 (inclusive) and bound
(exclusive). bound
must be greater than 0 and less than 230.
Random.full_int bound
returns a random integer between 0 (inclusive) and bound
(exclusive). bound
may be any positive integer.
If bound
is less than 230, Random.full_int bound
is equal to Random.int
bound
. If bound
is greater than 230 (on 64-bit systems or non-standard environments, such as JavaScript), Random.full_int
returns a value, where Random.int
raises Stdlib.Invalid_argument
.
Random.int32 bound
returns a random integer between 0 (inclusive) and bound
(exclusive). bound
must be greater than 0.
Random.int64 bound
returns a random integer between 0 (inclusive) and bound
(exclusive). bound
must be greater than 0.
Random.float bound
returns a random floating-point number between 0 and bound
(inclusive). If bound
is negative, the result is negative or zero. If bound
is 0, the result is 0.
let bits32: unit => Int32.t;
Random.bits32 ()
returns 32 random bits as an integer between Int32.min_int
and Int32.max_int
.
let bits64: unit => Int64.t;
Random.bits64 ()
returns 64 random bits as an integer between Int64.min_int
and Int64.max_int
.
The functions from module State
manipulate the current state of the random generator explicitly. This allows using one or several deterministic PRNGs, even in a multi-threaded program, without interference from other parts of the program.
module State: { ... };
let get_state: unit => State.t;
get_state()
returns a fresh copy of the current state of the domain-local generator (which is used by the basic functions).
let set_state: State.t => unit;
set_state s
updates the current state of the domain-local generator (which is used by the basic functions) by copying the state s
into it.