Dean Rasheed <dean.a.rash...@gmail.com> writes: > No. If x is 1e8 * y, then y will only affect the result in the 16th > place. You can see this if you do a simple series expansion:
> sqrt(1+yx^2) = 1 + 1/2 yx^2 + O(yx^4) Sigh, I went looking for that expansion yesterday and didn't find it. Should've tried harder. I was relying on a gut feeling that it would behave approximately like ln(1+x). > For most cases, the new algorithm is no more accurate than the old > one. The exception is when *both* x and y are very small. In this > case, it protects against incorrect underflows to 0. Yeah, I think you're right. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers