# fastparallel

> Zero-overhead asynchronous parallel/each/map function call

Latest version **2.4.1** (published 2021-10-19) · ISC license · 0 weekly downloads

## Install

```sh
npm install fastparallel
pnpm add fastparallel
yarn add fastparallel
bun add fastparallel
```

## Health

**Score 15/100 (F)** — status: abandoned.

Positive: no vulnerabilities.

Warnings: low downloads; no types; no esm support.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 2.4.1 |
| Published | 2021-10-19 |
| First published | 2015-03-14 |
| Weekly downloads | 0 |
| License | ISC |
| TypeScript types | none |
| Module format | CommonJS |
| Dependencies | 2 |
| Unpacked size | 23.3 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 169 |
| Author | Matteo Collina |
| Maintainers | matteo.collina |
| Keywords | parallel, fast, async |

## Links

- npm: https://www.npmjs.com/package/fastparallel
- Repository: https://github.com/mcollina/fastparallel
- Issues: https://github.com/mcollina/fastparallel/issues
- npm.io page: https://npm.io/package/fastparallel

## Dependencies (2)

- [xtend](https://npm.io/package/xtend.md) ^4.0.2
- [reusify](https://npm.io/package/reusify.md) ^1.0.4

## Alternatives

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## Recent versions

- 2.4.1 (latest) — 2021-10-19
- 2.4.0 — 2020-08-20
- 2.3.0 — 2016-05-23
- 2.2.1 — 2015-11-23
- 2.2.0 — 2015-11-23
- 2.1.0 — 2015-11-20
- 2.0.1 — 2015-10-02
- 2.0.0 — 2015-09-28
- 1.7.2 — 2015-09-22
- 1.7.1 — 2015-09-21
- 1.7.0 — 2015-09-13
- 1.6.1 — 2015-07-21
- 1.6.0 — 2015-07-13
- 1.5.3 — 2015-06-19
- 1.5.2 — 2015-06-17
- … 11 more at https://npm.io/package/fastparallel/versions

## README

# fastparallel [![ci](https://github.com/mcollina/fastparallel/actions/workflows/ci.yml/badge.svg)](https://github.com/mcollina/fastparallel/actions/workflows/ci.yml)

Zero-overhead parallel function call for node.js. Also supports each
and map!

Benchmark for doing 3 calls `setImmediate` 1 million times:

```
benchSetImmediate*1000000: 1378.514ms
benchAsyncParallel*1000000: 1740.304ms
benchAsyncEach*1000000: 1566.517ms
benchAsyncMap*1000000: 1687.518ms
benchNeoParallel*1000000: 1388.223ms
benchNeoEach*1000000: 1473.006ms
benchNeoMap*1000000: 1402.986ms
benchInsyncParallel*1000000: 1957.863ms
benchInsyncEach*1000000: 1383.822ms
benchInsyncMap*1000000: 1822.954ms
benchItemsParallel*1000000: 1690.118ms
benchParallelize*1000000: 1570.064ms
benchFastParallel*1000000: 1536.692ms
benchFastParallelNoResults*1000000: 1363.145ms
benchFastParallelEachResults*1000000: 1508.134ms
benchFastParallelEach*1000000: 1325.314ms
```

Obtained on node 12.18.2, on a dedicated server.

If you need zero-overhead series function call, check out
[fastseries](http://npm.im/fastseries). If you need a fast work queue
check out [fastq](http://npm.im/fastq). If you need to run fast
waterfall calls, use [fastfall](http://npm.im/fastfall).

[![js-standard-style](https://raw.githubusercontent.com/feross/standard/master/badge.png)](https://github.com/feross/standard)

__The major difference between version 1.x.x and 2.x.x is the order of
results__, this is now ready to replace async in every case.

## Example for parallel call

```js
var parallel = require('fastparallel')({
  // this is a function that will be called
  // when a parallel completes
  released: completed,

  // if you want the results, then here you are
  results: true
})

parallel(
  {}, // what will be this in the functions
  [something, something, something], // functions to call
  42, // the first argument of the functions
  done // the function to be called when the parallel ends
)

function something (arg, cb) {
  setImmediate(cb, null, 'myresult')
}

function done (err, results) {
  console.log('parallel completed, results:', results)
}

function completed () {
  console.log('parallel completed!')
}
```

## Example for each and map calls

```js
var parallel = require('fastparallel')({
  // this is a function that will be called
  // when a parallel completes
  released: completed,

  // if you want the results, then here you are
  // passing false disables map
  results: true
})

parallel(
  {}, // what will be this in the functions
  something, // functions to call
  [1, 2, 3], // the first argument of the functions
  done // the function to be called when the parallel ends
)

function something (arg, cb) {
  setImmediate(cb, null, 'myresult')
}

function done (err, results) {
  console.log('parallel completed, results:', results)
}

function completed () {
  console.log('parallel completed!')
}

```

## Caveats

The `done` function will be called only once, even if more than one error happen.

This library works by caching the latest used function, so that running a new parallel
does not cause **any memory allocations**.

## Why it is so fast?

1. This library is caching functions a lot.

2. V8 optimizations: thanks to caching, the functions can be optimized by V8 (if they are optimizable, and I took great care of making them so).

3. Don't use arrays if you just need a queue. A linked list implemented via processes is much faster if you don't need to access elements in between.

4. Accept passing a this for the functions. Thanks to this hack, you can extract your functions, and place them in a outer level where they are not created at every execution.

## License

ISC

---
_Source: https://npm.io/package/fastparallel · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._