toofast/Adder.js

The Node.js performance testing tool with unit-test-like API.

/**
 * An add operation sum that significantly reduces the numerical error in the total obtained by adding a
 * sequence of finite-precision floating-point numbers.
 *
 * @see {@link https://en.wikipedia.org/wiki/Kahan_summation_algorithm Kahan summation algorithm}
 */
export class Adder {
    constructor() {
        /**
         * The accumulated sum.
         */
        this._sum = 0;
        /**
         * A running compensation for lost low-order bits.
         */
        this._compensation = 0;
    }
    /**
     * The total sum of added measurements.
     */
    get sum() {
        return this._sum + this._compensation;
    }
    /**
     * Adds a new value to a sum.
     *
     * @param value The value to add.
     */
    add(value) {
        const { _sum } = this;
        const sum = _sum + value;
        this._compensation += Math.abs(_sum) < Math.abs(value) ? value - sum + _sum : _sum - sum + value;
        this._sum = sum;
    }
}