randu

Create an array containing uniformly distributed pseudorandom numbers between 0 and 1.

Usage

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

randu( len[, options] )

Returns an array containing uniformly distributed pseudorandom numbers between 0 and 1.

var out = randu( 10 );
// returns <Float64Array>

The function has the following parameters:

len: output array length.
options: function options.

The function accepts the following options:

dtype: output array data type. Must be a real-valued floating-point data type or "generic". Default: 'float64'.

By default, the function returns a Float64Array. To return an array having a different data type, set the dtype option.

var opts = {
    'dtype': 'generic'
};

var out = randu( 10, opts );
// returns [...]

randu.factory( [options] )

Returns a function for creating arrays containing uniformly distributed pseudorandom numbers between 0 and 1.

var random = randu.factory();

var out = random( 10 );
// returns <Float64Array>

var len = out.length;
// returns 10

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.
dtype: default output array data type. Must be a real-valued floating-point data type or "generic". Default: 'float64'.

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

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

var out = random( 10 );
// returns <Float64Array>

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

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

var out = random( 10, opts );
// returns <Float64Array>

The returned function accepts the following options:

dtype: output array data type. Must be a real-valued floating-point data type or "generic". This overrides the default output array data type.

To override the default output array data type, set the dtype option.

var random = randu.factory();

var out = random( 10 );
// returns <Float64Array>

var opts = {
    'dtype': 'generic'
};
out = random( 10, opts );
// returns [...]

randu.PRNG

The underlying pseudorandom number generator.

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

randu.seed

The value used to seed the underlying pseudorandom number generator.

var seed = randu.seed;

randu.seedLength

Length of underlying pseudorandom number generator seed.

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

randu.state

Writable property for getting and setting the underlying pseudorandom number generator state.

var state = randu.state;

randu.stateLength

Length of underlying pseudorandom number generator state.

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

randu.byteLength

Size (in bytes) of underlying pseudorandom number generator state.

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

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 function creation and not copied) and one sets the underlying generator state to a state array having a different length, the function returned by the factory method does not update the existing shared state and, instead, points to the newly provided state array. In order to synchronize the output of the underlying generator according to the new shared state array, the state array for each relevant creation function and/or PRNG must be explicitly set.
If PRNG state is "shared" and one sets the underlying generator state to a state array of the same length, the PRNG state is updated (along with the state of all other creation functions and/or PRNGs sharing the PRNG's state array).

Examples

var logEach = require( '@stdlib/console/log-each' );
var randu = require( '@stdlib/random/array/randu' );

// Create a function for generating random arrays originating from the same state:
var random = randu.factory({
    'state': randu.state,
    'copy': true
});

// Generate 3 arrays:
var x1 = random( 5 );
var x2 = random( 5 );
var x3 = random( 5 );

// Print the contents:
logEach( '%f, %f, %f', x1, x2, x3 );

// Create another function for generating random arrays with the original state:
random = randu.factory({
    'state': randu.state,
    'copy': true
});

// Generate a single array which replicates the above pseudorandom number generation sequence:
var x4 = random( 15 );

// Print the contents:
logEach( '%f', x4 );