En Sun, 04 May 2008 12:58:25 -0300, Duncan Booth <[EMAIL PROTECTED]> escribió:
> Szabolcs Horvát <[EMAIL PROTECTED]> wrote: > >> 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 ...)? > > There's a thread you might find interesting: > > http://groups.google.com/group/comp.lang.python/browse_thread/thread/9eda29faf92f532e/027cef7d4429aa3a > > In that thread I suggested that Python ought to implement sum by adding > together each pair of values, then each pair of results and so on. This > means that for input values of a similar magnitude the intermediate results > stay balanced. The implementation doesn't actually do all the first level Python doesn't require __add__ to be associative, so this should not be used as a general sum replacement. But if you know that you're adding floating point numbers you can use whatever algorithm best fits you. Or use numpy arrays; I think they implement Kahan summation or a similar algorithm. -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
