> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of > Menezes, Evandro > Sent: Friday, May 27, 2005 1:55 PM [...] > > That's because the error is the same but symmetrical for sin and > cos, so that, when you calculate the sum of their squares, one > cancels the other out. > > The lack of accuracy in x87 is well known: see > http://www.gnu.org/software/libc/manual/html_node/Errors-in-Math-F > unctions.html#Errors-in-Math-Functions.
Ulrich Drepper used a different method to compute math function accuracy, described here: http://people.redhat.com/drepper/libm/index.html It might be interesting to re-run the safe/unsafe/x87 tests using his methodology. His results show offer comparisons on a number of platforms, and the visual representation of the errors can offer some insight into the behavior of the implementation.
