On Sep 7, 2005, at 2:41 PM, Marshall Clow wrote:
At 3:41 PM -0500 9/6/05, Doug Gregor wrote:
On Sep 5, 2005, at 12:11 PM, Daryle Walker wrote:
On 9/3/05 1:00 PM, "Douglas Gregor" <dgregor@cs.indiana.edu> wrote:
Boost regression test failures ------------------------------ Report time: 2005-09-03T05:00:17Z [SNIP] Detailed report:
http://engineering.meta-comm.com/boost-regression/CVS-HEAD/ developer/ issues.ht ml [SNIP] |math| octonion_test: gcc-4_0-darwin gcc-4_0-darwin quaternion_test: gcc-4_0-darwin gcc-4_0-darwin special_functions_test: gcc-4_0-darwin gcc-4_0-darwin [TRUNCATE]
It looks like some code isn't handling the improved "long double" type very well.... (With Mac OS X Tiger 10.4 and GCC 4, the "long double" type is finally distinct and bigger than "double". The pre-Tiger warnings about not using "long double" are obviously removed. But it looks like the "double" version of "exp" is being used. Taking a quick look at a system "math.h"... I'm not sure there is a "long double" overload of "exp", just "expl".)
Sounds like we need to do some specializing for Tiger's GCC 4.0. Would you submit a patch to fix these problems?
in <cmath>, rather than <math.h>, there is: long double exp(long double __x);
I've traced through this, and the right "exp" is getting called. The machine epsilon for long double is: 4.9406564584124654417656879286822137236505980261432476442558568250067550 727020875e-324 There's no *way* we'll get that much accuracy out of the C library's sin/atan/cos/etc. Here's the result of a little program that prints out atan(1), 4*atan(1), and sin(4*atan(1)). There isn't a large enough improvement in precision from "double" to "long double": atan(1) with float = 0.785398185253143310546875 4*atan(1) with float = 3.1415927410125732421875 sin(4*atan(1)) with float = -8.74227765734758577309548854827880859375e-08 atan(1) with double = 0.78539816339744827899949086713604629039764404296875 4*atan(1) with double = 3.141592653589793115997963468544185161590576171875 sin(4*atan(1)) with double = 1.224606353822377258211417938582599163055419921875e-16 atan(1) with long double = 0.7853981633974483096282022398515465511081856675446033477783203125 4*atan(1) with long double = 3.14159265358979323851280895940618620443274267017841339111328125 sin(4*atan(1)) with long double = -5.42101086242752217003726400434970855712890625e-20 I don't even think that we can call this a platform bug; we just can't expect the C library routines to have that kind of precision. I think we should consider long double tests on this platform bogus and disable them. Doug