Re: [BUG?] log(2) flip/flopping

[Karim Belabas <Karim.Belabas@math.u-bordeaux1.fr>]

* Bill Allombert [2006-10-26 20:55]:
> On Wed, Oct 25, 2006 at 05:46:29PM -0700, Ilya Zakharevich wrote:
>> I discovered this by trying to investigate mysterious failures of
>> test suite of Math::Pari:
>> 
>>     ? log(2)
>>     %1 = 0.6931471805599453094172321215
>>     ? \p 38
>>        realprecision = 38 significant digits
>>     ? log(2)
>>     %2 = 0.69314718055994530941723212145817656808
>>     ? \p 58
>>        realprecision = 67 significant digits (58 digits displayed)
>>     ? log(2)
>>     %3 = 0.6931471805599453094172321214581765680755001343602552541207
>>     ? \p 38
>>        realprecision = 38 significant digits
>>     ? log(2)
>>     %4 = 0.69314718055994530941723212145817656807
>> 
>> Is this change between ...08 and ...07 as expected?
>> 
>> The code is in constlog2()...
> 
> This bug is known and recorded as bug #498.
> 
> The correct fix is to provide a version of constlog2 (and constpi and
> consteuler) which performs exact rounding.
> 
> I suppose we could easily improve constlog2() so that the rounding is more
> frequently correct.

The bug is now fixed in CVS.

Cheers,

    K.B.
-- 
Karim Belabas                  Tel: (+33) (0)5 40 00 26 17
Universite Bordeaux 1          Fax: (+33) (0)5 40 00 69 50
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