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

From: Glenn Schrader (gschrad_at_[hidden])
Date: 2007-02-16 12:36:15

Hmmm.

An absolute difference is:

    BOOST_CHECK_CLOSE( x, y, 1e-5 );

True??

so wouldn't a relative difference be:

    BOOST_CHECK_CLOSE( x / y, 1, 1e-5);
    or equivalently
    BOOST_CHECK_CLOSE( x, y, abs(y) * 1e-5);
    or maybe even
    BOOST_CHECK_CLOSE( x, y, max(abs(x),abs(y)) * 1e-5);

???

-glenn

Hugo Duncan wrote:
> Hi,
>
> Just to chime in with my problems using BOOST_CHECK_CLOSE ...
>
> I always have problems when checking for small numbers or zero.  I write  
> something like BOOST_CHECK_CLOSE(0,x,1e-5) and start wondering why it  
> fails, then rewrite the test using an epsilon value.
>
> When I know the value is going to be near zero this is ok, but sometimes  
> tests are written for computed values.  A possible solution would be to  
> have a check that uses the maximum of a relative and an absolute tolerance.
>
> Hugo
>
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