Re: [Boost-bugs] [Boost C++ Libraries] #13011: BOOST_TEST broken with floating point relational operators

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #13011: BOOST_TEST broken with floating point relational operators
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-05-06 00:39:45

#13011: BOOST_TEST broken with floating point relational operators
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  Reporter:  chris42f@…        |      Owner:  rogeeff
      Type:  Bugs              |     Status:  new
 Milestone:  To Be Determined  |  Component:  test
   Version:  Boost 1.63.0      |   Severity:  Regression
Resolution:                    |   Keywords:
-------------------------------+------------------------

Comment (by chris42f@…):

 Right, thanks for digging.  Honestly I didn't expect floating point
 comparison magic in BOOST_TEST by default, and was expecting to do my own
 epsilon testing.

 It's unfortunate that the default behavior fails some obvious desired
 properties at 0.0 - which as the additive identity is arguably the most
 commonly encountered value out of the entire floating point range.

 I'll admit that in the real use case, I was trying to do my own epsilon
 testing with a known absolute tolerance specific to the problem -
 something like

 {{{
 BOOST_TEST(fabs(a-b) < 1e-16)
 }}}

 which fails when a happens to be equal to b.  Overall, I'm not thrilled
 that boost tries to completely hide the problems of floating point
 comparison from users.

 For this case, it sounds like a solution with the current API is to use
 the obviously naive expression

 {{{
 BOOST_TEST(a == b)
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/13011#comment:2>
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