npm package: @stdlib/random-iter-minstd
Description: Create an iterator for a linear congruential pseudorandom number generator (LCG) based on Park and Miller.
Author: The Stdlib Authors
Latest version: 0.2.2

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# MINSTD

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> Create an iterator for a linear congruential pseudorandom number generator ([LCG][lcg]) based on Park and Miller.

<section class="installation">

## Installation

```bash
npm install @stdlib/random-iter-minstd
```

</section>

<section class="usage">

## Usage

```javascript
var iterator = require( '@stdlib/random-iter-minstd' );
```

#### iterator( \[options] )

Returns an iterator for generating pseudorandom numbers via a linear congruential pseudorandom number generator ([LCG][lcg]) based on Park and Miller.

```javascript
var it = iterator();
// returns <Object>

var r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

// ...
```

The function accepts the following `options`:

-   **normalized**: `boolean` indicating whether to return pseudorandom numbers on the interval `[0,1)`.
-   **seed**: pseudorandom number generator seed.
-   **state**: an [`Int32Array`][@stdlib/array/int32] 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 iterator has exclusive control over its internal pseudorandom number generator state. Default: `true`.
-   **iter**: number of iterations.

To return pseudorandom numbers on the interval `[0,1)`, set the `normalized` option.

```javascript
var it = iterator({
    'normalized': true
});

var r = it.next().value;
// returns <number>
```

To return an iterator having a specific initial state, set the iterator `state` option.

```javascript
var bool;
var it1;
var it2;
var r;
var i;

it1 = iterator();

// Generate pseudorandom numbers, thus progressing the generator state:
for ( i = 0; i < 1000; i++ ) {
    r = it1.next().value;
}

// Create a new iterator initialized to the current state of `it1`:
it2 = iterator({
    'state': it1.state
});

// Test that the generated pseudorandom numbers are the same:
bool = ( it1.next().value === it2.next().value );
// returns true
```

To seed the iterator, set the `seed` option.

```javascript
var it = iterator({
    'seed': 12345
});

var r = it.next().value;
// returns 207482415

it = iterator({
    'seed': 12345
});

r = it.next().value;
// returns 207482415
```

To limit the number of iterations, set the `iter` option.

```javascript
var it = iterator({
    'iter': 2
});

var r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

r = it.next().done;
// returns true
```

The returned iterator protocol-compliant object has the following properties:

-   **next**: function which returns an iterator protocol-compliant object containing the next iterated value (if one exists) assigned to a `value` property and a `done` property having a `boolean` value indicating whether the iterator is finished.
-   **return**: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.
-   **seed**: pseudorandom number generator seed.
-   **seedLength**: length of generator seed.
-   **state**: writable property for getting and setting the generator state.
-   **stateLength**: length of generator state.
-   **byteLength**: size (in bytes) of generator state.

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   If an environment supports `Symbol.iterator`, the returned iterator is iterable.
-   The generator has a period of approximately `2.1e9` (see [Numerical Recipes in C, 2nd Edition](#references), p. 279).
-   An [LCG][lcg] is fast and uses little memory. On the other hand, because the generator is a simple [linear congruential generator][lcg], the generator has recognized shortcomings. By today's PRNG standards, the generator's period is relatively short. More importantly, the "randomness quality" of the generator's output is lacking. These defects make the generator unsuitable, for example, in Monte Carlo simulations and in cryptographic applications.
-   If PRNG state is "shared" (meaning a state array was provided during iterator creation and **not** copied) and one sets the underlying generator state to a state array having a different length, the iterator 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 iterator 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 iterator and/or PRNGs sharing the PRNG's state array).

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var iterator = require( '@stdlib/random-iter-minstd' );

var it;
var r;

// Create a seeded iterator for generating pseudorandom numbers:
it = iterator({
    'seed': 1234,
    'iter': 10
});

// Perform manual iteration...
while ( true ) {
    r = it.next();
    if ( r.done ) {
        break;
    }
    console.log( r.value );
}
```

</section>

<!-- /.examples -->

* * *

<section class="references">

## References

-   Park, S. K., and K. W. Miller. 1988. "Random Number Generators: Good Ones Are Hard to Find." _Communications of the ACM_ 31 (10). New York, NY, USA: ACM: 1192–1201. doi:[10.1145/63039.63042][@park:1988].
-   Press, William H., Brian P. Flannery, Saul A. Teukolsky, and William T. Vetterling. 1992. _Numerical Recipes in C: The Art of Scientific Computing, Second Edition_. Cambridge University Press.

</section>

<!-- /.references -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/random-base/minstd`][@stdlib/random/base/minstd]</span><span class="delimiter">: </span><span class="description">A linear congruential pseudorandom number generator (LCG) based on Park and Miller.</span>
-   <span class="package-name">[`@stdlib/random-iter/minstd-shuffle`][@stdlib/random/iter/minstd-shuffle]</span><span class="delimiter">: </span><span class="description">create an iterator for a linear congruential pseudorandom number generator (LCG) whose output is shuffled.</span>
-   <span class="package-name">[`@stdlib/random-iter/mt19937`][@stdlib/random/iter/mt19937]</span><span class="delimiter">: </span><span class="description">create an iterator for a 32-bit Mersenne Twister pseudorandom number generator.</span>
-   <span class="package-name">[`@stdlib/random-iter/randi`][@stdlib/random/iter/randi]</span><span class="delimiter">: </span><span class="description">create an iterator for generating pseudorandom numbers having integer values.</span>
-   <span class="package-name">[`@stdlib/random-iter/randu`][@stdlib/random/iter/randu]</span><span class="delimiter">: </span><span class="description">create an iterator for generating uniformly distributed pseudorandom numbers between 0 and 1.</span>

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

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---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

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[umd]: https://github.com/umdjs/umd
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/random-iter-minstd/main/LICENSE

[lcg]: https://en.wikipedia.org/wiki/Linear_congruential_generator

[@park:1988]: http://dx.doi.org/10.1145/63039.63042

[@stdlib/array/int32]: https://www.npmjs.com/package/@stdlib/array-int32

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