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125 lines
3.6 KiB
125 lines
3.6 KiB
# fastparallel [](https://github.com/mcollina/fastparallel/actions/workflows/ci.yml)
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Zero-overhead parallel function call for node.js. Also supports each
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and map!
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Benchmark for doing 3 calls `setImmediate` 1 million times:
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```
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benchSetImmediate*1000000: 1378.514ms
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benchAsyncParallel*1000000: 1740.304ms
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benchAsyncEach*1000000: 1566.517ms
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benchAsyncMap*1000000: 1687.518ms
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benchNeoParallel*1000000: 1388.223ms
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benchNeoEach*1000000: 1473.006ms
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benchNeoMap*1000000: 1402.986ms
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benchInsyncParallel*1000000: 1957.863ms
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benchInsyncEach*1000000: 1383.822ms
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benchInsyncMap*1000000: 1822.954ms
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benchItemsParallel*1000000: 1690.118ms
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benchParallelize*1000000: 1570.064ms
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benchFastParallel*1000000: 1536.692ms
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benchFastParallelNoResults*1000000: 1363.145ms
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benchFastParallelEachResults*1000000: 1508.134ms
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benchFastParallelEach*1000000: 1325.314ms
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```
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Obtained on node 12.18.2, on a dedicated server.
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If you need zero-overhead series function call, check out
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[fastseries](http://npm.im/fastseries). If you need a fast work queue
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check out [fastq](http://npm.im/fastq). If you need to run fast
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waterfall calls, use [fastfall](http://npm.im/fastfall).
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[](https://github.com/feross/standard)
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__The major difference between version 1.x.x and 2.x.x is the order of
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results__, this is now ready to replace async in every case.
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## Example for parallel call
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```js
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var parallel = require('fastparallel')({
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// this is a function that will be called
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// when a parallel completes
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released: completed,
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// if you want the results, then here you are
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results: true
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})
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parallel(
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{}, // what will be this in the functions
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[something, something, something], // functions to call
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42, // the first argument of the functions
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done // the function to be called when the parallel ends
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)
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function something (arg, cb) {
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setImmediate(cb, null, 'myresult')
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}
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function done (err, results) {
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console.log('parallel completed, results:', results)
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}
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function completed () {
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console.log('parallel completed!')
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}
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```
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## Example for each and map calls
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```js
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var parallel = require('fastparallel')({
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// this is a function that will be called
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// when a parallel completes
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released: completed,
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// if you want the results, then here you are
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// passing false disables map
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results: true
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})
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parallel(
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{}, // what will be this in the functions
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something, // functions to call
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[1, 2, 3], // the first argument of the functions
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done // the function to be called when the parallel ends
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)
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function something (arg, cb) {
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setImmediate(cb, null, 'myresult')
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}
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function done (err, results) {
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console.log('parallel completed, results:', results)
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}
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function completed () {
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console.log('parallel completed!')
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}
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```
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## Caveats
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The `done` function will be called only once, even if more than one error happen.
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This library works by caching the latest used function, so that running a new parallel
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does not cause **any memory allocations**.
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## Why it is so fast?
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1. This library is caching functions a lot.
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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).
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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.
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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.
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## License
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ISC
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