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feat: add utils/async/parallel
PR-URL: #1896 Closes: #1811 Co-authored-by: Athan Reines <[email protected]> Co-authored-by: Philipp Burckhardt <[email protected]> Reviewed-by: Athan Reines <[email protected]> Reviewed-by: Philipp Burckhardt <[email protected]> Signed-off-by: Athan <[email protected]> Signed-off-by: Philipp Burckhardt <[email protected]> Co-authored-by: stdlib-bot <[email protected]>
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Diff for: ‎lib/node_modules/@stdlib/utils/async/parallel/README.md

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<!--
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@license Apache-2.0
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Copyright (c) 2024 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# parallel
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> Execute functions in parallel and pass the results of all functions to a provided callback.
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- Package usage documentation. -->
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<section class="usage">
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## Usage
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```javascript
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var parallel = require( '@stdlib/utils/async/parallel' );
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```
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#### parallel( fcns, \[options,] done )
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Executes a set of functions in parallel and passes the results of all functions to a provided callback.
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```javascript
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function a( clbk ) {
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setTimeout( onTimeout, 0 );
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function onTimeout() {
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clbk( null, 2 );
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}
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}
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function b( clbk ) {
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setTimeout( onTimeout, 0 );
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function onTimeout() {
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clbk( null, 4 );
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}
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}
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function done( error, out ) {
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if ( error ) {
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throw error;
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}
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console.log( out );
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// => [ 2, 4 ]
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}
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var fcns = [ a, b ];
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parallel( fcns, done );
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```
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The function accepts the following `options`:
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- **limit**: maximum number of functions to execute concurrently. Default: `infinity`.
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- **thisArg**: execution context for each function.
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To limit the maximum number of functions executing in parallel, set the `limit` option.
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```javascript
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function a( clbk ) {
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setTimeout( onTimeout, 0 );
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function onTimeout() {
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clbk( null, 2 );
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}
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}
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function b( clbk ) {
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setTimeout( onTimeout, 0 );
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function onTimeout() {
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clbk( null, 4 );
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}
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}
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function done( error, out ) {
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if ( error ) {
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throw error;
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}
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console.log( out );
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// => [ 2, 4 ]
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}
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var fcns = [ a, b ];
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var opts = {
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'limit': 1
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};
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parallel( fcns, opts, done );
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```
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To set the `this` context for **all** `functions` in the provided function array, set the `thisArg` option.
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```javascript
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function a( clbk ) {
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this.idx += 1;
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clbk( null, 2 );
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}
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function b( clbk ) {
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this.idx += 1;
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clbk( null, 4 );
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}
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var fcns = [ a, b ];
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var ctx = {
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'idx': 0
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};
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var opts = {
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'thisArg': ctx
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};
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parallel( fcns, opts, done );
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function done( error, out ) {
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if ( error ) {
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throw error;
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}
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console.log( ctx.idx );
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// => 2
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}
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```
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#### parallel.factory( fcns, \[options] )
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Returns a reusable function which executes a set of functions in parallel.
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```javascript
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function a( clbk ) {
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setTimeout( onTimeout, 0 );
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function onTimeout() {
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clbk( null, 2 );
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}
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}
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function b( clbk ) {
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setTimeout( onTimeout, 0 );
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function onTimeout() {
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clbk( null, 4 );
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}
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}
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function done( error, out ) {
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if ( error ) {
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throw error;
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}
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console.log( out );
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// => [ 2, 4 ]
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}
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var fcns = [ a, b ];
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var run = parallel.factory( fcns );
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run( done );
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run( done );
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run( done );
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```
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</section>
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<!-- /.usage -->
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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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## Notes
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- The order of the results provided to the `done` callback corresponds to the order of the provided functions.
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- When executed, each provided function is invoked with a single callback argument. The callback should be invoked upon function completion. The first argument is reserved as an `error` argument (which can be `null`). The second argument is reserved for any results which should be passed to the `done` callback upon completion of all provided functions.
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- If any function fails to invoke the callback argument, the `done` callback will never be invoked.
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- This implementation is intended to start asynchronous tasks so that execution of each task runs concurrently. If provided a function which does not perform asynchronous tasks, the function will execute synchronously. Hence, this implementation does **not** guarantee that execution is asynchronous. To do so, wrap the `done` callback in a `function` which either executes at the end of the current stack (e.g., `nextTick`) or during a subsequent turn of the event loop (e.g., `setImmediate`, `setTimeout`).
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- The function executes provided functions in the same thread. Accordingly, the function does **not** spawn new threads.
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</section>
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<!-- /.notes -->
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<!-- Package usage examples. -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var parallel = require( '@stdlib/utils/async/parallel' );
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function foo( clbk ) {
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setTimeout( onTimeout, 300 );
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function onTimeout() {
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clbk( null, 'one' );
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}
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}
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function bar( clbk ) {
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setTimeout( onTimeout, 100 );
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function onTimeout() {
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clbk( null, 'two' );
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}
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}
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function done( error, results ) {
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if ( error ) {
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throw error;
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}
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console.log( results );
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// => [ 'one', 'two' ]
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}
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var fcns = [ foo, bar ];
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parallel( fcns, done );
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```
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</section>
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<!-- /.examples -->
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<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="references">
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</section>
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<!-- /.references -->
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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
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<section class="related">
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</section>
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<!-- /.related -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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</section>
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<!-- /.links -->

Diff for: ‎lib/node_modules/@stdlib/utils/async/parallel/benchmark/benchmark.factory.js

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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2024 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var bench = require( '@stdlib/bench' );
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var pkg = require( './../package.json' ).name;
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var factory = require( './../lib/factory.js' );
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// FUNCTIONS //
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/**
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* Returns a function which runs asynchronously.
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*
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* @private
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* @param {*} value - return value
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* @returns {Function} function which runs asynchronously
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*/
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function fcn( value ) {
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return f;
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function f( clbk ) {
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setTimeout( onTimeout, 0 );
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function onTimeout() {
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clbk( null, value );
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}
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}
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}
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// MAIN //
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bench( pkg+':factory', function benchmark( b ) {
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var parallel;
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var arr;
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var i;
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arr = [
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fcn( 'one' ),
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fcn( 'two' ),
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fcn( 'three' ),
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fcn( 'four' )
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];
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parallel = factory( arr );
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i = 0;
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b.tic();
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return next();
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function next( error ) {
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i += 1;
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if ( error ) {
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b.fail( 'should not return an error' );
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}
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if ( i <= b.iterations ) {
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return parallel( next );
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}
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b.toc();
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b.pass( 'benchmark finished' );
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b.end();
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}
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});

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