chickadee » math » fpvector-sums

xs

f64vector

Computes the partial sums of the elements in xs in a way that incurs rounding error only once for each partial sum.

Example:

> (fpvector-sums
   #f64(1.0 1e-16 1e-16 1e-16 1e-16 1e+100 -1e+100))
#f64(1.0 1.0 1.0 1.0 1.0 1e+100 1.0)

Compare the same example computed by direct summation:

> (import srfi-1)
> (cdr
   (reverse
    (fold (lambda (x xs) (cons (+ x (first xs)) xs))
          (list 0.0)
          '(1.0 1e-16 1e-16 1e-16 1e-16 1e+100 -1e+100))))
'(1.0 1.0 1.0 1.0 1.0 1e+100 0.0)