artillery/dist/lib/core/weighted-pick.js

Cloud-scale load testing. https://www.artillery.io

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
import { pathToFileURL } from 'node:url';
import l from 'lodash';
export default create;
// naive implementation of selection with replacement
function create(list) {
    const dist = l.reduce(list, (acc, el, i) => {
        for (let j = 0; j < el.weight * 100; j++) {
            acc.push(i);
        }
        return acc;
    }, []);
    return () => {
        const i = dist[l.random(0, dist.length - 1)];
        return [i, list[i]];
    };
}
function bench() {
    const items = [
        { weight: 0, value: 'zero' },
        { weight: 1, value: 'a' },
        { weight: 2, value: 'b' },
        { weight: 3, value: 'c' },
        { weight: 4, value: 'd' },
        { weight: 5, value: 'e' },
        { weight: 1, value: 'f' },
        { weight: 2, value: 'g' },
        { weight: 3, value: 'h' },
        { weight: 4, value: 'i' },
        { weight: 5, value: 'j' },
        { weight: 10, value: 'k' }
    ];
    const picker = create(items);
    const ITERS = 10 ** 6;
    const startedAt = Date.now();
    const picks = l.map(l.range(ITERS), () => {
        const x = picker()[1];
        return x;
    });
    const delta = Date.now() - startedAt;
    console.log('ITERS = %s\ndelta = %s\nITERS/delta = %s', ITERS, delta, Math.round(ITERS / delta));
    const sumWeights = l.reduce(items, (acc, item) => acc + item.weight, 0);
    console.log('sumWeights = %s', sumWeights);
    l.each(items, (p) => {
        const count = l.filter(picks, { value: p.value }).length;
        console.log('Count of %s = %s (should be: %s%, is: %s%)', p.value, count, Math.round((p.weight / sumWeights) * 1000) / 1000, Math.round((count / ITERS) * 1000) / 1000);
    });
}
if (process.argv[1] &&
    import.meta.url === pathToFileURL(process.argv[1]).href) {
    bench();
}