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Bug#617894: marked as done ([ARMel] tgammal isn't accurate enough)

Your message dated Sun, 1 May 2011 17:25:47 +0200
with message-id <20110501152547.GA32333@hall.aurel32.net>
and subject line Re: Bug#617894: [ARMel] tgammal isn't accurate enough
has caused the Debian Bug report #617894,
regarding [ARMel] tgammal isn't accurate enough
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

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-- 
617894: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=617894
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--- Begin Message --- 
Package: libc6
Version: 2.11.2-13

The following piece of code :

#include <stdio.h>
#include <math.h>

int
main (int argc,
      char* argv[])
{
  long double x = 6.0;
  printf ("tgammal (%20Lf)=%20Lf\n", x, tgammal (x));
  return 0;
}

Prints, on an x86 debian unstable (eglibc 2.11.2-11) :
tgammal (            6.000000)=          120.000000
And on an ARMel debian unstable (eglibc 2.11.2-13) :
tgammal (6.00000000000000000000)=119.99999999999997157829
That last results if of too poor precision for sage (http://www.sagemath.org), which I'm porting to the platform.
The box used to run ubuntu, where the problem occurred too (https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/713985). 

Snark on #sage-devel

--- End Message ---
--- Begin Message --- 
On Sun, Mar 13, 2011 at 03:59:48PM +0100, Julien PUYDT wrote:
> Le 13/03/2011 15:49, Aurelien Jarno a écrit :
> >On Sat, Mar 12, 2011 at 03:27:31PM +0100, Julien PUYDT wrote:
> >>Isn't that a little short? If I read
> >>http://en.wikipedia.org/wiki/IEEE_754-2008#Basic_formats well, even
> >>simple precision boasts 23 digits.
> >
> >23 binary digits, which means 7.22 decimal digit. For double, it lists
> >15.95 digit, so your example is in the expected precision range.
> 
> Oh, dear! Indeed, I was counting the base 10 digits and comparing
> with base 2 digits... that was a stupid and shameful mistake!
> 
> Snark on #sage-devel
> 

As explained, tgammal() is in the expected accuracy on armel, given this
architecture has double = long double. I am therefore closing the bug.


-- 
Aurelien Jarno	                        GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net

--- End Message ---
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