FastTwoSum is Faster Than TwoSum

We all know that floating-point arithmetic is imprecise. When you do s = x + y , the value of s might not exactly be the sum of the values of x and y . Curiously (and importantly, for some applications), there's a way to quantify the imprecision: there's a family of algorithms 1 [ 1 Called "error-free transformations", because they transform x and y into s and e without any error in the sum. ]…