[Bug 713985] Re: [armel] Function tgammal has precision issues in version 2.12.1-0ubuntu10.2 on ARM
Dima Pasechnik
713985 at bugs.launchpad.net
Mon Jan 9 04:15:37 UTC 2012
The bug is in fact in lgammal, as tgammal(x) simply takes expl(lgammal(x));
namely, lgammal(6.0) produces 4.78749174278204581157 on armel,
while it should be closer to 4.7874917427820459942477, i.e. armel gives relative error of about 3.8e-17
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https://bugs.launchpad.net/bugs/713985
Title:
[armel] Function tgammal has precision issues in version
2.12.1-0ubuntu10.2 on ARM
Status in “eglibc” package in Ubuntu:
New
Bug description:
Consider the following test program :
#include <stdio.h>
#include <math.h>
int
main (int argc,
char* argv[])
{
long double x = 6.0;
printf("tgammal (%.20Lf)=%.20Lfn", x, tgammal(x));
return 0;
}
When run on 2.12.1-0ubuntu10.2, the result is :
tgammal (6.00000000000000000000)=119.99999999999997157829
while when run on 2.11.2-11 (glibc's unstable), the result is :
tgammal (6.00000000000000000000)=119.99999999999999998612
The second result is acceptable, while the second isn't. This makes
sage (http://www.sagemath.org) unhappy...
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