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 23:13:06

Got it, thank you so much 

Regards,
Georgios 

> On 30 Dec 2017, at 22:28, Raffi Enficiaud via Boost-users <boost-users_at_[hidden]> wrote:
> 
>> Le 30.12.17 à 14:41, Georgios Sermaidis via Boost-users a écrit :
>> 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] <mailto: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
> 
> Apart from creating a collection of differences that you compare with a
> collection of zeros (that can be wrap up in helper functions), I do not
> see a way to use this facility as is. Looping over the elements would
> certainly be the most maintainable and easy to understand choice.
> 
> Raffi
> 
> 
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