* [Bug math/16560] spurious underflow exception from exp2/exp10
2014-02-12 9:53 [Bug math/16560] New: spurious underflow exception from exp2 zimmerma+gcc at loria dot fr
@ 2014-02-12 10:44 ` zimmerma+gcc at loria dot fr
2014-02-12 10:51 ` zimmerma+gcc at loria dot fr
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From: zimmerma+gcc at loria dot fr @ 2014-02-12 10:44 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=16560
Paul Zimmermann <zimmerma+gcc at loria dot fr> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|spurious underflow |spurious underflow
|exception from exp2 |exception from exp2/exp10
--- Comment #1 from Paul Zimmermann <zimmerma+gcc at loria dot fr> ---
idem in double precision with exp10:
Testing function exp10 for exponent 0 [seed=14309].
rounding mode MPFR_RNDN:
wrong underflow flag for x=4.0000000000000@-269
library gives 1.0000000000000
mpfr gives 1.0000000000000
underflow: mpfr 0, library 16
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2014-02-12 9:53 [Bug math/16560] New: spurious underflow exception from exp2 zimmerma+gcc at loria dot fr
2014-02-12 10:44 ` [Bug math/16560] spurious underflow exception from exp2/exp10 zimmerma+gcc at loria dot fr
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--- Comment #2 from Paul Zimmermann <zimmerma+gcc at loria dot fr> ---
same in double precision (for exp2):
Testing function exp2 for exponent 0 [seed=14309].
rounding mode MPFR_RNDN:
wrong underflow flag: mpfr gives 0, library 16
x=4.0000000000000@-269
library gives 1.0000000000000
mpfr gives 1.0000000000000
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2014-02-12 9:53 [Bug math/16560] New: spurious underflow exception from exp2 zimmerma+gcc at loria dot fr
2014-02-12 10:44 ` [Bug math/16560] spurious underflow exception from exp2/exp10 zimmerma+gcc at loria dot fr
2014-02-12 10:51 ` zimmerma+gcc at loria dot fr
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--- Comment #3 from Paul Zimmermann <zimmerma+gcc at loria dot fr> ---
and in extended precision for exp2:
Testing function exp2 for exponent 0 [seed=16203].
rounding mode MPFR_RNDN:
wrong underflow flag: mpfr gives 0, library 16
x=8.0000000000000000@-4112
library gives 1.0000000000000000
mpfr gives 1.0000000000000000
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--- Comment #4 from Paul Zimmermann <zimmerma+gcc at loria dot fr> ---
and in extended precision for exp10:
Testing function exp10 for exponent 0 [seed=16203].
rounding mode MPFR_RNDN:
wrong underflow flag: mpfr gives 0, library 16
x=8.0000000000000000@-4112
library gives 1.0000000000000000
mpfr gives 1.0000000000000000
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--- Comment #5 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=03a7091fa2afc84e215fc99fceca52baa4b0f8f1
commit 03a7091fa2afc84e215fc99fceca52baa4b0f8f1
Author: Joseph Myers <joseph@codesourcery.com>
Date: Thu Mar 27 18:41:14 2014 +0000
Fix x86/x86_64 expl/exp10l spurious underflows (bug 16348).
This patch fixes bug 16348, spurious underflows from x86/x86_64 expl
on arguments close to 0. These implementations effectively use expm1
(on the fractional part of the argument) internally, so resulting in
spurious underflows when the result is very close to 1. For arguments
small enough that the round-to-nearest correct result is 1, this patch
uses 1+x instead.
These implementations are also used for exp10l and so the patch fixes
similar issues there (the 0x1p-67 threshold being small enough to be
correct for exp10l as well as expl). But because of spurious
underflows in other exp10 implementations (bug 16560), the tests
aren't added for exp10 at this point - they can be added when the
other exp10 parts of that bug are fixed.
Tested x86_64 and x86; no ulps updates needed.
[BZ #16348]
* sysdeps/i386/fpu/e_expl.S (IEEE754_EXPL) [!USE_AS_EXPM1L]: Use
1+x for argument with exponent below -67.
* sysdeps/x86_64/fpu/e_expl.S (IEEE754_EXPL) [!USE_AS_EXPM1L]:
Likewise.
* math/auto-libm-test-in: Add more tests of exp.
* math/auto-libm-test-out: Regenerated.
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 10 +
NEWS | 10 +-
math/auto-libm-test-in | 18 ++
math/auto-libm-test-out | 666 +++++++++++++++++++++++++++++++++++++++++++
sysdeps/i386/fpu/e_expl.S | 10 +-
sysdeps/x86_64/fpu/e_expl.S | 10 +-
6 files changed, 715 insertions(+), 9 deletions(-)
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2014-02-12 9:53 [Bug math/16560] New: spurious underflow exception from exp2 zimmerma+gcc at loria dot fr
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Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Flags| |security-
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2014-02-12 9:53 [Bug math/16560] New: spurious underflow exception from exp2 zimmerma+gcc at loria dot fr
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--- Comment #6 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
This is an automated email from the git hooks/post-receive script. It was
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commit a638de828d877376fb238efc8b0bc9220dd2601e
Author: Joseph Myers <joseph@codesourcery.com>
Date: Wed Jun 25 11:33:22 2014 +0000
Fix exp10 spurious underflows (bug 16560).
This patch fixes spurious underflows from exp10 for arguments near 0
(part of bug 16560; that bug also includes spurious underflows from
exp2, which are not fixed by this patch). The problem is underflows
in the internal computation converting the exp10 argument to arguments
for exp (with extra precision), and the fix is simply to return 1
early for arguments near enough to 0 (just as arguments with large
enough magnitude have their own overflow / underflow logic at the
start of the function).
Tested x86_64 and x86 and ulps updated accordingly; also tested for
powerpc32 and mips64 to validate the ldbl-128ibm and ldbl-128 changes.
[BZ #16560]
* sysdeps/ieee754/dbl-64/e_exp10.c (__ieee754_exp10): Return 1 for
arguments close to 0.
* sysdeps/ieee754/ldbl-128/e_exp10l.c (__ieee754_exp10l):
Likewise.
* sysdeps/ieee754/ldbl-128ibm/e_exp10l.c (__ieee754_exp10l):
Likewise.
* math/auto-libm-test-in: Add more tests of exp10.
* math/auto-libm-test-out: Regenerated.
* sysdeps/x86_64/fpu/libm-test-ulps: Update.
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 11 +
math/auto-libm-test-in | 18 +
math/auto-libm-test-out | 666 ++++++++++++++++++++++++++++++++
sysdeps/ieee754/dbl-64/e_exp10.c | 2 +
sysdeps/ieee754/ldbl-128/e_exp10l.c | 2 +
sysdeps/ieee754/ldbl-128ibm/e_exp10l.c | 2 +
sysdeps/x86_64/fpu/libm-test-ulps | 8 +
7 files changed, 709 insertions(+), 0 deletions(-)
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--- Comment #8 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
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commit 03d95bd48319256bd29cfaece45919fc58bf56cc
Author: Joseph Myers <joseph@codesourcery.com>
Date: Thu Feb 12 19:02:45 2015 +0000
Fix exp2 spurious underflows (bug 16560).
This patch fixes the remaining part of bug 16560, spurious underflows
from exp2 of arguments close to 0 (when the result is close to 1, so
should not underflow), by just using 1+x instead of a more complicated
calculation when the argument is sufficiently small.
Tested for x86_64, x86 and mips64.
[BZ #16560]
* math/e_exp2l.c [LDBL_MANT_DIG == 106] (LDBL_EPSILON): Undefine
and redefine.
(__ieee754_exp2l): Do not multiply small fractional parts by
M_LN2l.
* sysdeps/i386/fpu/e_exp2l.S (__ieee754_exp2l): Just add 1 to
small argument.
* sysdeps/ieee754/dbl-64/e_exp2.c (__ieee754_exp2): Likewise.
* sysdeps/ieee754/flt-32/e_exp2f.c (__ieee754_exp2f): Likewise.
* sysdeps/x86_64/fpu/e_exp2l.S (__ieee754_exp2l): Likewise.
* math/auto-libm-test-in: Add more tests of exp2.
* math/auto-libm-test-out: Regenerated.
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 15 +
NEWS | 2 +-
math/auto-libm-test-in | 18 +
math/auto-libm-test-out | 666 ++++++++++++++++++++++++++++++++++++++
math/e_exp2l.c | 9 +
sysdeps/i386/fpu/e_exp2l.S | 10 +-
sysdeps/ieee754/dbl-64/e_exp2.c | 3 +
sysdeps/ieee754/flt-32/e_exp2f.c | 3 +
sysdeps/x86_64/fpu/e_exp2l.S | 10 +-
9 files changed, 733 insertions(+), 3 deletions(-)
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To: glibc-bugs
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Joseph Myers <jsm28 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #9 from Joseph Myers <jsm28 at gcc dot gnu.org> ---
Fixed for 2.22.
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