bizcharts
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bizcharts
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JavaScript
;
/* from @antv */
Object.defineProperty(exports, "__esModule", { value: true });
/**
* Our default sum is the [Kahan-Babuska algorithm](https://pdfs.semanticscholar.org/1760/7d467cda1d0277ad272deb2113533131dc09.pdf).
* This method is an improvement over the classical
* [Kahan summation algorithm](https://en.wikipedia.org/wiki/Kahan_summation_algorithm).
* It aims at computing the sum of a list of numbers while correcting for
* floating-point errors. Traditionally, sums are calculated as many
* successive additions, each one with its own floating-point roundoff. These
* losses in precision add up as the number of numbers increases. This alternative
* algorithm is more accurate than the simple way of calculating sums by simple
* addition.
*
* This runs on `O(n)`, linear time in respect to the array.
*
* @param {Array<number>} x input
* @return {number} sum of all input numbers
* @example
* sum([1, 2, 3]); // => 6
*/
function sumFnc(x) {
// If the array is empty, we needn't bother computing its sum
if (x.length === 0) {
return 0;
}
// Initializing the sum as the first number in the array
var sum = x[0];
// Keeping track of the floating-point error correction
var correction = 0;
var transition;
for (var i = 1; i < x.length; i++) {
transition = sum + x[i];
// Here we need to update the correction in a different fashion
// if the new absolute value is greater than the absolute sum
if (Math.abs(sum) >= Math.abs(x[i])) {
correction += sum - transition + x[i];
}
else {
correction += x[i] - transition + sum;
}
sum = transition;
}
// Returning the corrected sum
return sum + correction;
}
exports.default = sumFnc;
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