locutus/esm/python/math/fsum.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

export function fsum(...values) {
    //      discuss at: https://locutus.io/python/fsum/
    // parity verified: Python 3.12
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Uses compensated summation for better floating-point precision than naive accumulation.
    //       example 1: fsum(1e16, 1, -1e16)
    //       returns 1: 1
    //       example 2: fsum(0.1, 0.2, 0.3)
    //       returns 2: 0.6
    //       example 3: fsum(1, 2, 3, 4)
    //       returns 3: 10
    let sum = 0;
    let compensation = 0;
    for (const value of values) {
        const x = Number(value);
        if (Number.isNaN(x)) {
            return Number.NaN;
        }
        const t = sum + x;
        if (Math.abs(sum) >= Math.abs(x)) {
            compensation += sum - t + x;
        }
        else {
            compensation += x - t + sum;
        }
        sum = t;
    }
    return sum + compensation;
}