Re: [Boost-users] Boost.Test: floating point comparison using absolute diference

Subject: Re: [Boost-users] Boost.Test: floating point comparison using absolute diference
From: Georgios Sermaidis (g.sermaidis_at_[hidden])
Date: 2017-12-30 13:41:22

Thank you. Is there a way to achieve this when comparing collections, i.e. when using boost::test_tools::per_element()?

> On 29 Dec 2017, at 19:37, Raffi Enficiaud via Boost-users <boost-users_at_[hidden]> wrote:
> 
> Le 29.12.17 à 17:33, Georgios Sermaidis via Boost-users a écrit :
>> Hi all,
>> 
>> I am trying to find a way to make the boost unit test framework use an
>> absolute difference for floating point comparison instead of the
>> relative difference. 
>> I searched the documentation to try to find a suitable decorator but
>> couldn’t find anything. Any help is much appreciated!
>> 
>> #defineBOOST_TEST_MODULEexample
>> 
>> #include<boost/test/included/unit_test.hpp>
>> 
>> 
>> //boost::unit_test::toleranceusesrelativedifference and hence this test
>> will pass; 
>> 
>> // isthereanythingIcanusehereto indicateabsolutedifference?
>> 
>> BOOST_AUTO_TEST_CASE(my_test,*boost::unit_test::tolerance(0.1))
>> 
>> {
>> 
>> 
>> BOOST_TEST(10.1==10.3);
>> 
>> }
> 
> What you want to do is discussed here in the doc:
> http://www.boost.org/doc/libs/1_66_0/libs/test/doc/html/boost_test/testing_tools/extended_comparison/floating_point/floating_points_comparison_impl.html
> 
> You may just use
> 
> BOOST_TEST(left - right == .0, boost::unit_test::tolerance(0.1));
> 
> and I think it should use absolute tolerance on the absolute value of
> left-right.
> 
> If nothing works, there is always the good old comparison:
> BOOST_TEST((std::abs(left - right) < 0.1))
> 
> Note the double parenthesis, in this case BOOST_TEST will see only the
> evaluation of the expression inside, which is cast to bool (less
> elegant, but should work as last resort).
> 
> Raffi
> 
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