code: def decker_sum(a, b):
      
      x = a + b
      y = b - (x - a) if abs(a) > abs(b) else a - (x - b)
      return x, y
docs: Computationally equivalent to knuth_sum, but formally a bit cheaper.
      Only works for floats though (and not arrays), and the branch make it in
      fact less favorable in terms of actual speed.