On Wed, Apr 13, 2016, at 12:51, Robin Becker wrote: > Does anyone know if sum does anything special to try and improve > accuracy? My > simple tests seem to show it is exactly equivalent to a for loop > summation.
No, it doesn't. Sum works on any type that can be added (except strings), it can't make any assumptions about the characteristics of floating point types. For non-numeric types, the addition operator may not be semantically commutative or associative. Look at http://code.activestate.com/recipes/393090-binary-floating-point-summation-accurate-to-full-p/ for an example of a more accurate algorithm, but note that, for example, this algorithm wouldn't work on complex numbers (you'd have to sum the real and imaginary components separately) -- https://mail.python.org/mailman/listinfo/python-list
