Re: [boost] Boost Test Library: general floating point comparisons

From: Gennadiy Rozental (gennadiy.rozental_at_[hidden])
Date: 2007-02-16 02:28:26

"Jody Hagins" <jody-boost-011304_at_[hidden]> wrote in message 
news:20070214152529.6fd1187d.jody-boost-011304_at_atdesk.com...
> On Wed, 14 Feb 2007 11:03:04 -0500
> "Gennadiy Rozental" <gennadiy.rozental_at_[hidden]> wrote:
>
>> Latest version contains two macros: one for percentage based
>> comparison, one  for fraction based one.
>
> Great!  I'll take a look when it is released.
>
>
>> > The interface requiring percentages is bad enough.  The explanations
>> > in the documentation are even worse.
>>
>> Do you have any particular complains?
>
> Nothing particular, other than I could not understand how to use it.  I
> even tried several examples myself.  I would call it with hard coded
> values that I thought should fail, and it would pass.  I had similar

Could you please provide an example?

> problems on the other side where tests I though should pass would fail.

And here also

> So, I just stopped trying to use it.
>
>
>> > Just to remind everyone, I'm a strong supporter of Boost.Test, and
>> > have stated so many times.  Unfortunately, that macro causes more
>> > problems than it solves.
>>
>> Could you please clarify.
>
>
> For me, it is too cumbersome, and the definition of "close" is obscure.

How is it cumbersome? From my understanding cumbersome is a synonym to 
inconvinient. What particularly inconvinient you see in the 
BOOST_CHECK_CLOSE?

> I had several tests that used the macro, and the tests started failing
> on valid values.  Changing how the macro was invoked caused previously
> passing tests to fail.  Obviously, I was missing something badly.

Yet again. Please provide an examples.

> I ended up reverting back to a poor, but at least well understood,
> principle of using an epsilon value as it was appropriate for those
> situations.
>
>
>> Docs says: " Last third parameter defines the tolerance for the
>> comparison  in percentage units". This combined with example and error
>> message produced:
>>
>> test.cpp(4) : error in test_main: difference between v1{1.23456e-10}
>> and  v2{1.23457e-10} exeeds 1e-04%
>>
>> should give you some level of understanding. Try explaining now
>> fraction  based comparisons to anyone not an expert.
>>
>> But if you are willing to provide an updated version for the pages
>> related  to the FP comparison you are very welcome
>
>
> I would be very willing, however I simply do not understand the current
> interface so I doubt I could explaint it to anyone.  I know the docs are
> there.  However, after reading them, I'm still in the dark.  I can't
> prove the inadequacy, only state that I am unable to properly use the
> interface based on the docs and examples.

At some point Paul promised shed some light  in a form of FPV comparison 
tools docs. It never happened though. I will have to get to this once I am 
done with the rest. Though I still not sure why this tool causing that much 
misunderstanding.

Gennadiy