Re: [Boost-users] unit test and BOOST_CHECK_CLOSE

From: Vladimir Krasovsky (vkrasovsky_at_[hidden])
Date: 2005-02-17 07:16:14

Hello Thomas,

Thursday, February 17, 2005, 1:35:48 PM, you wrote:

Thomas> dear list,

Thomas> When executing a test defined by:
Thomas> BOOST_CHECK_CLOSE(t3.x(3), 0.0, epsilon);

Thomas> I get the message:
Thomas> difference between t3.x(3){2.34188e-17} and 0.0{0} exceeds 1e-08%

Thomas> where obviously the difference does not exceeds the given threshold 1e-08...

Thomas> What's going on ?

As I remember, tolerance should be given in percents.
See
http://www.boost.org/libs/test/doc/components/test_tools/floating_point_comparison.html
for more detailed description of algorithm used in BOOST_CHECK_CLOSE.

Either I do not understand something or you cannot use BOOST_CHECK_CLOSE for
direct comparison with 0.0. Inequations given never satisfied in case
one of arguments is zero. I think you could write

BOOST_CHECK(t3.x(3) >= -epsilon && t3.x(3) <= epsilon);

given that epsilon is non-negative.

-- 
Best regards,
 Vladimir                            mailto:vkrasovsky_at_[hidden]