randu

Usage

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

randu()

Returns a uniformly distributed pseudorandom number on the interval [0,1).

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

randu.factory( [options] )

Returns a pseudorandom number generator (PRNG) for generating uniformly distributed random numbers on the interval [0,1).

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

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

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

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

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

var rand2 = randu.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 = randu();
}

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

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

randu.NAME

The generator name.

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

randu.PRNG

The underlying pseudorandom number generator.

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

randu.MIN

Minimum value lower bound.

var min = randu.MIN;
// returns 0.0

randu.MAX

Maximum value upper bound (not greater than 1 exclusive).

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

randu.seed

The value used to seed randu().

var rand;
var r;
var i;

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

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

randu.seedLength

Length of generator seed.

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

randu.state

Writable property for getting and setting the generator state.

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

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

// ...

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

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

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

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

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

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

// ...

randu.stateLength

Length of generator state.

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

randu.byteLength

Size (in bytes) of generator state.

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

randu.toJSON()

Serializes the pseudorandom number generator as a JSON object.

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