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From: "newbie-02 at gmx dot de" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug math/28472] pow(10, i) accuracy
Date: Sun, 14 Nov 2021 05:38:00 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28472

--- Comment #5 from b. <newbie-02 at gmx dot de> ---
if ... I'm right in testing ... Intel 'oneAPI' compiler(s) 'icpx' and 'dpcp=
p'
produce clean powers of 10 ( matching E-string evaluation ) for long double
figures with 'exp10l( x )'.=20=20

since they do not compile themselves but use clang/clang++ for this purpose=
 -
with a huge bunch of options and includes - it should be possible to have a
look at it and gather some inspiration ... ??? hot spots seem to be calling
clang with '-cc1' and '-x c++'.=20=20

( for the bug itself i propose testing and setting to new, besides the
deviation it is a consistency problem which is difficult to explain to user=
s:
that one get's different results in one system for different formulations of
the same  mathematical task. ('pow( 10, x )' !=3D '1Ex' !=3D 'pow10( x )' !=
=3D
'exp10( x )' ).=20=20

( and of course gcc shouldn't be second in 'best compilers' )=20

reg. the proposal of using exp10( x ) instead of pow( 10, x ):=20=20
'exp10( x )' compiled with gcc -O2: 230 fails between x =3D -324 and x =3D =
308,=20
'pow( 10, x )': only 2,=20
as well with 'exp10( x )'=20
( complaining " incompatible implicit declaration of built-in function =E2=
=80=98exp10=E2=80=99
" )=20
as for '__builtin_exp10( x )'.=20=20
as well for gcc, g++, clang++,=20
'clang' additional complaints and producing even more fails.

--=20
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