Boost logo

Boost :

From: Markus Schöpflin (markus.schoepflin_at_[hidden])
Date: 2005-04-19 07:14:53

Daniel James wrote:
> Markus Schöpflin <markus.schoepflin <at>> writes:
>>I have to admit, following Victor's argumentation, I don't see the
>>fundamental difference between the failures on SunOS and on Tru64.
> On SunOS gcc the hash function is giving the same result for
> std::numeric_limits<long double>::max(), std::numeric_limits<long double>
> ::max()/2 and std::numeric_limits<long double>::max()/4. This indicates that
> the function for getting its exponent is probably treating the value as a
> double. If you're using a long double you want to take advantage of its
> increased accuracy and range but the hash function is loosing that information
> and so could give bad results under certain circumstances.

Thanks for the explanation.

>>>The tests don't supply a general purpose hash testing suite, but one
>>>that tests whether the hash functions are doing what I expect.
>>I don't get you there. The tests are supposed to tell whether the hash
>>library works ok or not on some particular compiler/platform. If some of
>>the tests fail, I have to assume (from a user's point of view) that the
>>library will not work reliably for me. (Especially as these are not
>>compilation failures but runtime failures.)
> This isn't released code, I wouldn't assume that it would work reliably at all.
> It might not even be fully included in the next release. When we reach the code
> freeze I'll add annotations to the tests to explain what's going on. I might
> also make some changes so that only real failures show up - but taking this too
> far would make the tests essentially useless. (An early version didn't take
> into account a float's sign, it met the hash specifications, but I'd consider
> that a bug).

I was under the impression that hash functions would be part of the
upcoming release. Just to clarify, my intention was not to complain about a
not working hash library but to understand/clarify _why_ the regression
reports showed a failure for this platform.

>>Maybe you could change the tests to just print the hash values on stdout?
> But then the results won't show up on the summary. At the moment it's more
> useful that the test summary shows me useful information.

Do you know about "always_show_run_output"? You just have to add
"<test-info>always_show_run_output" to your hash-test rule to always see
the output of the test runs.


Boost list run by bdawes at, gregod at, cpdaniel at, john at