On 7 Des, 06:43, dbd <d...@ieee.org> wrote: > If you have > samples of a sine wave with peak amplitude of one half eps, the "abs(x- > y) < eps" test would report all values on the sine wave as equal to > zero. This would not be correct.
You don't understand this at all do you? If you have a sine wave with an amplitude less than the truncation error, it will always be approximately equal to zero. Numerical maths is about approximations, not symbolic equalities. > 1.0 + eps is the smallest value greater than 1.0, distinguishable from > 1.0. Which is the reason 0.5*eps*sin(x) is never distinguishable from 0. > A constant comparison value is not appropriate. That require domain specific knowledge. Sometimes we look at a significant number of digits; sometimes we look at a fixed number of decimals; sometimes we look at abs(y/x). But there will always be a truncation error of some sort, and differences less than that is never significant. > > Mark was right, DaveA's discussion explains a strategy to use. > > Dale B. Dalrymple -- http://mail.python.org/mailman/listinfo/python-list
