"Gabriel Genellina" <[EMAIL PROTECTED]> wrote: > 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/9 >> eda29faf92f532e/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. > Yes, my argument is more along the line that it should have been implemented that way in the first place, but changing things now would require time machine intervention. :)
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