Szabolcs Horvát <[EMAIL PROTECTED]> writes: [...] > A little research shows that Mathematica uses a "compensated > summation" algorithm. Indeed, using the algorithm described at > http://en.wikipedia.org/wiki/Kahan_summation_algorithm > gives us a result around ~ 10^-17: > > def compSum(arr): > s = 0.0 > c = 0.0 > for x in arr: > y = x-c > t = s+y > c = (t-s) - y > s = t > return s > > mean = compSum(data)/len(data) > print compSum(x - mean for x in data)/len(data) > > > I thought that it would be very nice if the built-in sum() function > used this algorithm by default. Has this been brought up before? > Would this have any disadvantages (apart from a slight performance > impact, but Python is a high-level language anyway ...)? > > Szabolcs Horvát
sum() works for any sequence of objects with an __add__ method, not just floats! Your algorithm is specific to floats. -- Arnaud -- http://mail.python.org/mailman/listinfo/python-list
