Why would I use 2's complement to compare two doubles instead of comparing their differences against an epsilon value?

Question

Referenced here and here...Why would I use two's complement over an epsilon method? It seems like the epsilon method would be good enough for most cases.

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Update: I'm purely looking for a theoretical reason why you'd use one over the other. I've always used the epsilon method.

Has anyone used the 2's complement comparison successfully? Why? Why Not?

Answer 1

the second link you reference mentions an article that has quite a long description of the issue:

http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm

but unless you are tweaking performance I would stick with epsilon so people can debug your code