fastparallel

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

Benchmark for doing 3 calls setImmediate 1 million times:

non-reusable setImmediate: 1781ms
async.parallel: 3484ms
async.each: 2621ms
async.map: 3054ms
neoAsync.parallel: 2162ms
neoAsync.each: 2156ms
neoAsync.map: 2080ms
insync.parallel: 10252ms
insync.each: 2397ms
insync.map: 9700ms
items.parallel: 3725ms
parallelize: 2928ms
fastparallel with results: 2139ms
fastparallel without results: 1957ms
fastparallel map: 2102ms
fastparallel each: 1941ms

These benchmarks where taken via bench.js on node v4.2.2, on a MacBook Pro Retina Mid 2014 (i7, 16GB of RAM).

If you need zero-overhead series function call, check out fastseries. If you need a fast work queue check out fastq. If you need to run fast waterfall calls, use fastfall.

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

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

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?

This library is caching functions a lot.
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).
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.
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