Problem with BOOST_CHECK_CLOSE_FRACTION

Question

I'm using the Boost::Test library, and I am trying to check if an actual percent value is close to the expected value:

BOOST_CHECK_CLOSE_FRACTION(
    items[i].ExpectedPercent,
    items[i].ActualCount / totalCount,
    0.05);

For some reason this check fails even when the values are close enough:

difference between items[i].ExpectedPercent{0.40000000000000002}
   and items[i].ActualCount / totalReturned{0.42999999999999999}
                                    exceeds 0.050000000000000003

Is this a problem with Boost or a problem with how I am using Boost?

iano · Accepted Answer · 2010-01-21T23:54:37.343

4

After some testing, it turns out that the documentation for BOOST_CHECK_CLOSE_FRACTION is incorrect. The tolerance should be specified as a fraction of the expected value.

So, TFAE:

BOOST_CHECK(abs(x - y) < (min(x, y) * 0.1));
BOOST_CHECK_CLOSE(x, y, 10);
BOOST_CHECK_CLOSE_FRACTION(x, y, 0.1);

edited Jan 21 '10 at 23:54

answered Jan 21 '10 at 23:46

iano

2,061
1
18
22

1

I'd suggest you to check if there is a related report in Boost Trac and if not, report it there or send your comment to Boost mailing list. – mloskot Feb 19 '10 at 17:08

score 2 · Answer 2 · answered Jan 21 '10 at 23:20

2

It is a problem with how you are using boost.

The last argument is a percent tolerance, not an absolute variance value. 5% of 0.4 is 0.02.

answered Jan 21 '10 at 23:20

Omnifarious

54,333
19
131
194

score 1 · Answer 3 · answered Dec 26 '13 at 18:19

1

Obviously BOOST_CHECK_CLOSE and BOOST_CHECK_CLOSE_FRACTION won't work if you check if something is near 0. Then you can use:

BOOST_CHECK(abs(x - y) < accurancy);

answered Dec 26 '13 at 18:19

Janek Olszak

4,067
1
28
22

Problem with BOOST_CHECK_CLOSE_FRACTION

3 Answers3

Linked