Tim Peters <t...@python.org> added the comment:
Across millions of tries, same thing: Windows exp2 is off by at least 1 ulp over a third of the time, and by over 2 ulp about 3 times per million. Still haven't seen pow(2, x) off by as much as 0.52 ulp. >From its behavior, it appears Windows implements exp2(x) like so: i = floor(x) x -= i # now 0 <= x < 1 return ldexp(exp2(x), i) So it's apparently using some sub-state-of-the-art approximation to 2**x over the domain [0, 1]. But a consequence is that it gets it exactly right whenever x is an integer, so it's unlikely anyone will notice it's sloppy ;-) I expect we should just live with it. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue45917> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com