At Sun, 24 Dec 2006 13:35:14 +0100, Michel Van den Bergh wrote: > I was looking at the code for gsl_sum. I have not completely > understood it yet, but I noticed that whereas levin_utrunc.c > explicitly tests for terms that are zero, this is not the case for > levin_u.c. As one divides by such terms, it seems that one may > potentially divide by zero this way. Am I wrong?
Hello, Thanks for your email. I think the original code that the routine was translated from assumes that all terms passed in are non-zero since any others would not contribute to the sum. > The documentation does not seem to mention that terms should be > different from zero. Yes, I will add a note about that. > I am not a numerical analyst (IANANA) but it seems to me that even in > levin_utrunc.c no motivation is given for discarding zero terms. > Wouldn't it be more natural to add a bit of noise to the remainder > estimates to reduce the risk of division by zero? Generally in GSL we just implement what is published in the literature, so far I have not seen any newer algorithms published. -- best regards, Brian Gough (GSL Maintainer) Network Theory Ltd, Publishing the GSL Manual - http://www.network-theory.co.uk/gsl/manual/ _______________________________________________ Help-gsl mailing list Help-gsl@gnu.org http://lists.gnu.org/mailman/listinfo/help-gsl
