#12320: install cephes on the ARM platform
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Reporter: dimpase | Owner: jason, jkantor
Type: defect | Status: needs_info
Priority: major | Milestone: sage-5.0
Component: numerical | Keywords: cephes, numerical noise, ARM,
Cygwin, gammal, lgammal
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Comment(by dimpase):
Replying to [comment:3 Snark]:
> I'm trying to track down the numerical glitches related to the lgammal
libm(in glibc) implementation, as discussed on the ubuntu glibc
[https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/713985 ticket], as
fixing the problem upstream looks like a better option in that case.
>
> So far, I think I tracked down the implementation in either in
sysdeps/ieee754/ldbl-128/e_lgammal_r.c or
sysdeps/ieee754/ldbl-96/e_lgammal_r.c. The problem is that I don't know
which is compiled in, as I don't even see those in any Makefile!
no, the trouble is in sysdeps/ieee754/ldbl-64/e_lgammal_r.c
It is actually the one that gets called. (long double is 8 bit on armel).
You can check this as follows:
{{{
/* foo.c */
#include <stdio.h>
#include <math.h>
int
main (int argc, char* argv[])
{
long double x = 6.0;
int i;
printf("lgammal (%.20Lf)=%.20Lf\n", x, lgammal(x));
printf("__lgamma (%.20Lf)=%.20Lf\n", x, __ieee754_lgamma_r(x,&i));
printf("tgammal (%.20Lf)=%.20Lf\n", x, tgammal(x));
printf("__gamma (%.20Lf)=%.20Lf\n", x, __ieee754_gamma_r(x,&i));
return 0;
}
}}}
Compile this with a static linking:
{{{
gcc foo.c /usr/lib/arm-linux/gnueabi/libm.a
}}}
Running it you see:
{{{
lgammal (6.00000000000000000000)=4.78749174278204581157
__lgamma (6.00000000000000000000)=4.78749174278204581157
tgammal (6.00000000000000000000)=119.99999999999997157829
__gamma (6.00000000000000000000)=119.99999999999997157829
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12320#comment:6>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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