randi

Pseudorandom numbers having integer values.

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': [] }

Notes

  • Warning: the default underlying source of pseudorandom numbers may change in the future. If exact reproducibility is required, either explicitly specify a PRNG via the name option or use an underlying PRNG directly.
  • If PRNG state is "shared" (meaning a state array was provided during PRNG creation and not copied) and one sets the generator state to a state array having a different length, the PRNG does not update the existing shared state and, instead, points to the newly provided state array. In order to synchronize PRNG output according to the new shared state array, the state array for each relevant PRNG must be explicitly set.
  • If PRNG state is "shared" and one sets the generator state to a state array of the same length, the PRNG state is updated (along with the state of all other PRNGs sharing the PRNG's state array).

Examples

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

var seed;
var rand;
var i;

// Generate pseudorandom numbers...
for ( i = 0; i < 100; i++ ) {
    console.log( randi() );
}

// Create a new pseudorandom number generator...
seed = 1234;
rand = randi.factory({
    'seed': seed
});
for ( i = 0; i < 100; i++ ) {
    console.log( rand() );
}

// Create another pseudorandom number generator using a previous seed...
rand = randi.factory({
    'seed': randi.seed
});
for ( i = 0; i < 100; i++ ) {
    console.log( rand() );
}