randi

Usage

var randi = require( '@stdlib/random/base/randi' );

randi()

Returns a pseudorandom number having an integer value.

var v = randi();
// returns <number>

randi.factory( [options] )

Returns a pseudorandom number generator (PRNG) for generating random numbers.

var rand = randi.factory();

The function accepts the following options:

• name: name of a supported pseudorandom number generator (PRNG), which will serve as the underlying source of pseudorandom numbers. The following generators are supported:

  • mt19937: 32-bit Mersenne Twister.
  • minstd: linear congruential pseudorandom number generator (LCG) based on Park and Miller.
  • minstd-shuffle: linear congruential pseudorandom number generator (LCG) whose output is shuffled.

  Default: 'mt19937'.

• seed: pseudorandom number generator seed. Valid seed values vary according to the underlying PRNG.

• state: pseudorandom number generator state. Valid state values vary according to the underlying PRNG. If provided, the function ignores the seed option.

• copy: boolean indicating whether to copy a provided pseudorandom number generator state. Setting this option to false allows sharing state between two or more pseudorandom number generators. Setting this option to true ensures that a returned generator has exclusive control over its internal state. Default: true.

By default, the underlying pseudorandom number generator is mt19937. To use a different PRNG, set the name option.

var rand = randi.factory({
    'name': 'minstd-shuffle'
});

var v = rand();
// returns <number>

To seed a pseudorandom number generator, set the seed option.

var rand1 = randi.factory({
    'seed': 12345
});

var r1 = rand1();
// returns <number>

var rand2 = randi.factory({
    'seed': 12345
});

var r2 = rand2();
// returns <number>

var bool = ( r1 === r2 );
// returns true

To return a generator having a specific initial state, set the generator state option.

var rand;
var bool;
var r;
var i;

// Generate pseudorandom numbers, thus progressing the generator state:
for ( i = 0; i < 1000; i++ ) {
    r = randi();
}

// Create a new PRNG initialized to the current state of `randi`:
rand = randi.factory({
    'state': randi.state
});

// Test that the generated pseudorandom numbers are the same:
bool = ( rand() === randi() );
// returns true

randi.NAME

The generator name.

var str = randi.NAME;
// returns 'randi'

randi.PRNG

The underlying pseudorandom number generator.

var prng = randi.PRNG;
// returns <Function>

randi.MIN

Minimum value lower bound (specific to underlying PRNG).

var min = randi.MIN;
// returns <number>

randi.MAX

Maximum value upper bound (specific to underlying PRNG).

var max = randi.MAX;
// returns <number>

randi.seed

The value used to seed randi().

var rand;
var v;
var i;

// Generate pseudorandom values...
for ( i = 0; i < 100; i++ ) {
    v = randi();
}

// Generate the same pseudorandom values...
rand = randi.factory({
    'seed': randi.seed
});
for ( i = 0; i < 100; i++ ) {
    v = rand();
}

randi.seedLength

Length of generator seed.

var len = randi.seedLength;
// returns <number>

randi.state

Writable property for getting and setting the generator state.

var r = randi();
// returns <number>

r = randi();
// returns <number>

// ...

// Get a copy of the current state:
var state = randi.state;

r = randi();
// returns <number>

r = randi();
// returns <number>

// Reset the state:
randi.state = state;

// Replay the last two pseudorandom numbers:
r = randi();
// returns <number>

r = randi();
// returns <number>

// ...

randi.stateLength

Length of generator state.

var len = randi.stateLength;
// returns <number>

randi.byteLength

Size (in bytes) of generator state.

var sz = randi.byteLength;
// returns <number>

randi.toJSON()

Serializes the pseudorandom number generator as a JSON object.

var o = randi.toJSON();
// returns { 'type': 'PRNG', 'name': '...', 'state': {...}, 'params': [] }