npm package: @stdlib/os-num-cpus
Description: Number of CPUs.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
  </summary>
  <p>We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.</p>
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</details>

# Number of CPUs

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Number of CPUs.

<section class="installation">

## Installation

```bash
npm install @stdlib/os-num-cpus
```

</section>

<section class="usage">

## Usage

```javascript
var NUM_CPUS = require( '@stdlib/os-num-cpus' );
```

#### NUM_CPUS

Number of CPUs.

```javascript
var n = NUM_CPUS;
// returns <number>
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   In a web browser, the number of CPUs is determined by querying the hardware concurrency [API][hardware-concurrency].
-   Otherwise, the number of CPUs is determined via the [os][node-os] module.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- run-disable -->

<!-- eslint-disable node/no-process-exit -->

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

```javascript
var proc = require( 'process' );
var cluster = require( 'cluster' );
var NUM_CPUS = require( '@stdlib/os-num-cpus' );

var i;

function onTimeout() {
    proc.exit( 0 );
}

if ( cluster.isMaster ) {
    for ( i = 0; i < NUM_CPUS; i++ ) {
        cluster.fork();
    }
} else {
    console.log( 'Worker %s. Process id: %d.', cluster.worker.id, cluster.worker.process.pid );

    setTimeout( onTimeout, 1000 );
}
```

</section>

<!-- /.examples -->



<!-- 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/os-num-cpus-cli`][@stdlib/os-num-cpus-cli]</span><span class="delimiter">: </span><span class="description">CLI package for use as a command-line utility.</span>


</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->


<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

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

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

</section>

<!-- /.stdlib -->

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<section class="links">

[@stdlib/os-num-cpus-cli]: https://www.npmjs.com/package/@stdlib/os-num-cpus-cli

[npm-image]: http://img.shields.io/npm/v/@stdlib/os-num-cpus.svg
[npm-url]: https://npmjs.org/package/@stdlib/os-num-cpus

[test-image]: https://github.com/stdlib-js/os-num-cpus/actions/workflows/test.yml/badge.svg?branch=v0.2.3
[test-url]: https://github.com/stdlib-js/os-num-cpus/actions/workflows/test.yml?query=branch:v0.2.3

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/os-num-cpus/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/os-num-cpus?branch=main

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[stdlib]: https://github.com/stdlib-js/stdlib

[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors

[cli-section]: https://github.com/stdlib-js/os-num-cpus#cli
[cli-url]: https://github.com/stdlib-js/os-num-cpus/tree/cli
[@stdlib/os-num-cpus]: https://github.com/stdlib-js/os-num-cpus/tree/main

[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

[deno-url]: https://github.com/stdlib-js/os-num-cpus/tree/deno
[deno-readme]: https://github.com/stdlib-js/os-num-cpus/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/os-num-cpus/tree/umd
[umd-readme]: https://github.com/stdlib-js/os-num-cpus/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/os-num-cpus/tree/esm
[esm-readme]: https://github.com/stdlib-js/os-num-cpus/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/os-num-cpus/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/os-num-cpus/main/LICENSE

[node-os]: https://nodejs.org/api/os.html#os_os_cpus

[hardware-concurrency]: https://developer.mozilla.org/en-US/docs/Web/API/NavigatorConcurrentHardware/hardwareConcurrency

</section>

<!-- /.links -->