https://github.com/stdlib-js/utils-parallel
Execute scripts in parallel.
https://github.com/stdlib-js/utils-parallel
concurrency concurrent exec execute javascript multi-core multi-cpu multi-process node node-js nodejs parallel runner stdlib util utilities utility utils worker workers
Last synced: 27 days ago
JSON representation
Execute scripts in parallel.
- Host: GitHub
- URL: https://github.com/stdlib-js/utils-parallel
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-15T17:45:44.000Z (over 4 years ago)
- Default Branch: main
- Last Pushed: 2026-02-07T22:35:10.000Z (about 1 month ago)
- Last Synced: 2026-02-08T06:51:01.170Z (about 1 month ago)
- Topics: concurrency, concurrent, exec, execute, javascript, multi-core, multi-cpu, multi-process, node, node-js, nodejs, parallel, runner, stdlib, util, utilities, utility, utils, worker, workers
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 671 KB
- Stars: 3
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Citation: CITATION.cff
- Security: SECURITY.md
- Notice: NOTICE
Awesome Lists containing this project
README
About stdlib...
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The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.
When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.
To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!
# Parallel
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Execute scripts in parallel.
## Installation
```bash
npm install @stdlib/utils-parallel
```
Alternatively,
- To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).
- If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).
- For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).
- To use as a general utility for the command line, install the corresponding [CLI package][cli-section] globally.
The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.
To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.
## Usage
```javascript
var parallel = require( '@stdlib/utils-parallel' );
```
#### parallel( files, \[options,] clbk )
Executes scripts in parallel.
```text
var files = [
'./a.js',
'./b.js'
];
function done( error ) {
if ( error ) {
console.error( 'Exit code: '+error.code );
console.error( 'Signal: '+error.signal );
throw error;
}
console.log( 'Done!' );
}
parallel( files, done );
```
The function accepts the following `options`:
- **cmd**: executable file/command. Default: `'node'`.
- **workers**: number of workers. Default: number of CPUs minus `1`.
- **concurrency**: number of scripts to execute concurrently. Default: `options.workers`.
- **ordered**: `boolean` indicating whether to preserve the order of script output. Default: `false`.
- **maxBuffer**: maximum child process `stdio` buffer size. This option is **only** applied when `options.ordered = true`. Default: `200*1024*1024` bytes.
- **uid**: child process user identity.
- **gid**: child process group identity.
By default, the number of workers running scripts is equal to the number of CPUs minus `1` (master process). To adjust the number of workers, set the `workers` option.
```text
var files = [
'./a.js',
'./b.js'
];
function done( error ) {
if ( error ) {
console.error( 'Exit code: '+error.code );
console.error( 'Signal: '+error.signal );
throw error;
}
console.log( 'Done!' );
}
var opts = {
'workers': 8
};
parallel( files, opts, done );
```
By default, the number of scripts running concurrently is equal to the number of workers. To adjust the concurrency, set the `concurrency` option.
```text
var files = [
'./a.js',
'./b.js'
];
function done( error ) {
if ( error ) {
console.error( 'Exit code: '+error.code );
console.error( 'Signal: '+error.signal );
throw error;
}
console.log( 'Done!' );
}
var opts = {
'concurrency': 6
};
parallel( files, opts, done );
```
By specifying a concurrency greater than the number of workers, a worker may be executing more than `1` script at any one time. While not likely to be advantageous for synchronous scripts, setting a higher concurrency may be advantageous for scripts performing asynchronous tasks.
By default, each script is executed as a [Node.js][node-js] script.
```text
$ node
```
To run scripts via an alternative executable or none at all, set the `cmd` option.
```text
var files = [
'./a.js',
'./b.js'
];
function done( error ) {
if ( error ) {
console.error( 'Exit code: '+error.code );
console.error( 'Signal: '+error.signal );
throw error;
}
console.log( 'Done!' );
}
var opts = {
'cmd': '' // e.g., if scripts contain a shebang
};
parallel( files, opts, done );
```
By default, the `stdio` output for each script is interleaved; i.e., the `stdio` output from one script **may** be interleaved with the `stdio` output from one or more other scripts. To preserve the `stdio` output order for each script, set the `ordered` option to `true`.
```text
var files = [
'./a.js',
'./b.js'
];
function done( error ) {
if ( error ) {
console.error( 'Exit code: '+error.code );
console.error( 'Signal: '+error.signal );
throw error;
}
console.log( 'Done!' );
}
var opts = {
'ordered': true
};
parallel( files, opts, done );
```
## Notes
- Relative file paths are resolved relative to the current working directory.
- Ordered script output does **not** imply that scripts are executed in order. To preserve script order, execute the scripts sequentially via some other means.
- Script concurrency cannot exceed the number of scripts.
- If the script concurrency is less than the number of workers, the number of workers is reduced to match the specified concurrency.
## Examples
```javascript
var fs = require( 'fs' );
var path = require( 'path' );
var writeFileSync = require( '@stdlib/fs-write-file' ).sync;
var unlinkSync = require( '@stdlib/fs-unlink' ).sync;
var parallel = require( '@stdlib/utils-parallel' );
function template( id ) {
var file = '';
file += '\'use strict\';';
file += 'var id;';
file += 'var N;';
file += 'var i;';
file += 'id = '+id+';';
file += 'N = 1e5;';
file += 'console.log( \'File: %s. id: %s. N: %d.\', __filename, id, N );';
file += 'for ( i = 0; i < N; i++ ) {';
file += 'console.log( \'id: %s. v: %d.\', id, i );';
file += '}';
return file;
}
function createDir() {
var dir = path.join( __dirname, 'examples', 'tmp' );
fs.mkdirSync( dir );
return dir;
}
function createScripts( dir, nFiles ) {
var content;
var fpath;
var files;
var i;
files = [];
for ( i = 0; i < nFiles; i++ ) {
content = template( i.toString() );
fpath = path.join( dir, i+'.js' );
writeFileSync( fpath, content, {
'encoding': 'utf8'
});
files.push( fpath );
}
return files;
}
var nFiles = 10;
// Make a temporary directory to store files:
var dir = createDir();
// Create temporary files:
var files = createScripts( dir, nFiles );
// Set the runner options:
var opts = {
'concurrency': 3,
'workers': 3,
'ordered': false
};
// Run all temporary scripts:
parallel( files, opts, done );
function done( error ) {
if ( error ) {
console.log( error.message );
}
cleanup();
console.log( 'Done!' );
}
function cleanup() {
var i;
// Delete the temporary files...
for ( i = 0; i < files.length; i++ ) {
unlinkSync( files[ i ] );
}
// Remove temporary directory:
fs.rmdirSync( dir );
}
```
* * *
## CLI
## Installation
To use as a general utility, install the CLI package globally
```bash
npm install -g @stdlib/utils-parallel-cli
```
### Usage
```text
Usage: parallel [options] ...
Options:
-h, --help Print this message.
-V, --version Print the package version.
--cmd cmd Executable file/command.
--workers num Number of workers.
--concurrency num Number of scripts to run concurrently.
--ordered Preserve order of script output.
--uid uid Process user identity.
--gid gid Process group identity.
--maxbuffer size Max buffer size for stdout and stderr.
```
### Examples
```bash
$ parallel --cmd 'node' --workers 4 --concurrency 8 ./1.js ./2.js ./3.js ./4.js ./5.js ./6.js ./7.js ./8.js ./9.js ./10.js
```
* * *
## 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 © 2016-2026. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/utils-parallel.svg
[npm-url]: https://npmjs.org/package/@stdlib/utils-parallel
[test-image]: https://github.com/stdlib-js/utils-parallel/actions/workflows/test.yml/badge.svg?branch=v0.3.4
[test-url]: https://github.com/stdlib-js/utils-parallel/actions/workflows/test.yml?query=branch:v0.3.4
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-parallel/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/utils-parallel?branch=main
[chat-image]: https://img.shields.io/badge/zulip-join_chat-brightgreen.svg
[chat-url]: https://stdlib.zulipchat.com
[stdlib]: https://github.com/stdlib-js/stdlib
[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors
[cli-section]: https://github.com/stdlib-js/utils-parallel#cli
[cli-url]: https://github.com/stdlib-js/utils-parallel/tree/cli
[@stdlib/utils-parallel]: https://github.com/stdlib-js/utils-parallel/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/utils-parallel/tree/deno
[deno-readme]: https://github.com/stdlib-js/utils-parallel/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/utils-parallel/tree/umd
[umd-readme]: https://github.com/stdlib-js/utils-parallel/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/utils-parallel/tree/esm
[esm-readme]: https://github.com/stdlib-js/utils-parallel/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/utils-parallel/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-parallel/main/LICENSE
[node-js]: http://nodejs.org/