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util: improve spliceOne perf #20453

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util: improve spliceOne perf #20453

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1d05c45
util: improve spliceOne perf
apapirovski May 1, 2018
d770149
fixup: address nit
apapirovski May 1, 2018
14ed2f2
fixup: implement feedback
apapirovski May 1, 2018
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22 changes: 22 additions & 0 deletions benchmark/util/splice-one.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
'use strict';

const common = require('../common');

const bench = common.createBenchmark(main, {
n: [1e7],
size: [10, 100, 500],
}, { flags: ['--expose-internals'] });

function main({ n, size, type }) {
const { spliceOne } = require('internal/util');
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I'm curious, why put this here?

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The benchmark runs with --expose-internals so the main function has access to them but the outside doesn't.

const arr = new Array(size);
arr.fill('');
const pos = Math.floor(size / 2);

bench.start();
for (var i = 0; i < n; i++) {
spliceOne(arr, pos);
arr.push('');
}
bench.end(n);
}
7 changes: 4 additions & 3 deletions lib/internal/util.js
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Expand Up @@ -322,10 +322,11 @@ function join(output, separator) {
return str;
}

// About 1.5x faster than the two-arg version of Array#splice().
// As of V8 6.6, depending on the size of the array, this is anywhere
// between 1.5-10x faster than the two-arg version of Array#splice()
function spliceOne(list, index) {
for (var i = index, k = i + 1, n = list.length; k < n; i += 1, k += 1)
list[i] = list[k];
for (; index + 1 < list.length; index++)
list[index] = list[index + 1];
list.pop();
}

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