stdlib-js
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Improved Ziggurat Method
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Standard normally distributed pseudorandom numbers using the [Improved Ziggurat][ziggurat-algorithm] method.
bash
npm install @stdlib/random-base-improved-ziggurat
javascript
var randn = require( '@stdlib/random-base-improved-ziggurat' );
#### randn()
Returns a standard normally distributed pseudorandom number.
javascript
var r = randn();
// returns <number>
#### randn.factory( [options] )
Returns a pseudorandom number generator (PRNG) for generating standard normally distributed pseudorandom numbers.
javascript
var rand = randn.factory();
The function accepts the following options:
- prng: pseudorandom number generator for generating uniformly distributed pseudorandom numbers on the interval [0,1). If provided, the function ignores both the state and seed options. In order to seed the returned pseudorandom number generator, one must seed the provided prng (assuming the provided prng is seedable).
- seed: pseudorandom number generator seed.
- state: a [Uint32Array][@stdlib/array/uint32] containing pseudorandom number generator state. 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.
To use a custom PRNG as the underlying source of uniformly distributed pseudorandom numbers, set the prng option.
javascript
var minstd = require( '@stdlib/random-base-minstd' );
var rand = randn.factory({
'prng': minstd.normalized
});
var r = rand();
// returns <number>
To seed a pseudorandom number generator, set the seed option.
javascript
var rand1 = randn.factory({
'seed': 12345
});
var r1 = rand1();
// returns <number>
var rand2 = randn.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.
javascript
var rand;
var bool;
var r;
var i;
// Generate pseudorandom numbers, thus progressing the generator state:
for ( i = 0; i < 1000; i++ ) {
r = randn();
}
// Create a new PRNG initialized to the current state of `randn`:
rand = randn.factory({
'state': randn.state
});
// Test that the generated pseudorandom numbers are the same:
bool = ( rand() === randn() );
// returns true
#### randn.NAME
The generator name.
javascript
var str = randn.NAME;
// returns 'improved-ziggurat'
#### randn.PRNG
The underlying pseudorandom number generator for uniformly distributed numbers on the interval [0,1).
javascript
var prng = randn.PRNG;
// returns <Function>
#### randn.seed
The value used to seed randn().
javascript
var rand;
var r;
var i;
// Generate pseudorandom values...
for ( i = 0; i < 100; i++ ) {
r = randn();
}
// Generate the same pseudorandom values...
rand = randn.factory({
'seed': randn.seed
});
for ( i = 0; i < 100; i++ ) {
r = rand();
}
If provided a PRNG for uniformly distributed numbers, this value is null.
javascript
var rand = randn.factory({
'prng': Math.random
});
var seed = rand.seed;
// returns null
#### randn.seedLength
Length of generator seed.
javascript
var len = randn.seedLength;
// returns <number>
If provided a PRNG for uniformly distributed numbers, this value is null.
javascript
var rand = randn.factory({
'prng': Math.random
});
var len = rand.seedLength;
// returns null
#### randn.state
Writable property for getting and setting the generator state.
javascript
var r = randn();
// returns <number>
r = randn();
// returns <number>
// ...
// Get a copy of the current state:
var state = randn.state;
// returns <Uint32Array>
r = randn();
// returns <number>
r = randn();
// returns <number>
// Reset the state:
randn.state = state;
// Replay the last two pseudorandom numbers:
r = randn();
// returns <number>
r = randn();
// returns <number>
// ...
If provided a PRNG for uniformly distributed numbers, this value is null.
javascript
var rand = randn.factory({
'prng': Math.random
});
var state = rand.state;
// returns null
#### randn.stateLength
Length of generator state.
javascript
var len = randn.stateLength;
// returns <number>
If provided a PRNG for uniformly distributed numbers, this value is null.
javascript
var rand = randn.factory({
'prng': Math.random
});
var len = rand.stateLength;
// returns null
#### randn.byteLength
Size (in bytes) of generator state.
javascript
var sz = randn.byteLength;
// returns <number>
If provided a PRNG for uniformly distributed numbers, this value is null.
javascript
var rand = randn.factory({
'prng': Math.random
});
var sz = rand.byteLength;
// returns null
#### randn.toJSON()
Serializes the pseudorandom number generator as a JSON object.
javascript
var o = randn.toJSON();
// returns { 'type': 'PRNG', 'name': '...', 'state': {...}, 'params': [] }
If provided a PRNG for uniformly distributed numbers, this method returns null.
javascript
var rand = randn.factory({
'prng': Math.random
});
var o = rand.toJSON();
// returns null
javascript
var randn = require( '@stdlib/random-base-improved-ziggurat' );
var seed;
var rand;
var i;
// Generate pseudorandom numbers...
for ( i = 0; i < 100; i++ ) {
console.log( randn() );
}
// Create a new pseudorandom number generator...
seed = 1234;
rand = randn.factory({
'seed': seed
});
for ( i = 0; i < 100; i++ ) {
console.log( rand() );
}
// Create another pseudorandom number generator using a previous seed...
rand = randn.factory({
'seed': randn.seed
});
for ( i = 0; i < 100; i++ ) {
console.log( rand() );
}
@stdlib/random-iter/improved-ziggurat][@stdlib/random/iter/improved-ziggurat]: create an iterator for generating pseudorandom numbers drawn from a standard normal distribution using the Improved Ziggurat algorithm.
- [@stdlib/random-streams/improved-ziggurat][@stdlib/random/streams/improved-ziggurat]: create a readable stream for generating pseudorandom numbers drawn from a standard normal distribution using the Improved Ziggurat algorithm.
