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glibc/sysdeps/generic
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Joseph Myers a5721ebc68 Fix clog, clog10 inaccuracy (bug 19016). 
For arguments with X^2 + Y^2 close to 1, clog and clog10 avoid large
errors from log(hypot) by computing X^2 + Y^2 - 1 in a way that avoids
cancellation error and then using log1p.

However, the thresholds for using that approach still result in log
being used on argument as large as sqrt(13/16) > 0.9, leading to
significant errors, in some cases above the 9ulp maximum allowed in
glibc libm.  This patch arranges for the approach using log1p to be
used in any cases where |X|, |Y| < 1 and X^2 + Y^2 >= 0.5 (with the
existing allowance for cases where one of X and Y is very small),
adjusting the __x2y2m1 functions to work with the wider range of
inputs.  This way, log only gets used on arguments below sqrt(1/2) (or
substantially above 1), where the error involved is much less.

Tested for x86_64, x86, mips64 and powerpc.  For the ulps regeneration
I removed the existing clog and clog10 ulps before regenerating to
allow any reduced ulps to appear.  Tests added include those found by
random test generation to produce large ulps either before or after
the patch, and some found by trying inputs close to the (0.75, 0.5)
threshold where the potential errors from using log are largest.

	[BZ #19016]
	* sysdeps/generic/math_private.h (__x2y2m1f): Update comment to
	allow more cases with X^2 + Y^2 >= 0.5.
	* sysdeps/ieee754/dbl-64/x2y2m1.c (__x2y2m1): Likewise.  Add -1 as
	normal element in sum instead of special-casing based on values of
	arguments.
	* sysdeps/ieee754/dbl-64/x2y2m1f.c (__x2y2m1f): Update comment.
	* sysdeps/ieee754/ldbl-128/x2y2m1l.c (__x2y2m1l): Likewise.  Add
	-1 as normal element in sum instead of special-casing based on
	values of arguments.
	* sysdeps/ieee754/ldbl-128ibm/x2y2m1l.c (__x2y2m1l): Likewise.
	* sysdeps/ieee754/ldbl-96/x2y2m1.c [FLT_EVAL_METHOD != 0]
	(__x2y2m1): Update comment.
	* sysdeps/ieee754/ldbl-96/x2y2m1l.c (__x2y2m1l): Likewise.  Add -1
	as normal element in sum instead of special-casing based on values
	of arguments.
	* math/s_clog.c (__clog): Handle more cases using log1p without
	hypot.
	* math/s_clog10.c (__clog10): Likewise.
	* math/s_clog10f.c (__clog10f): Likewise.
	* math/s_clog10l.c (__clog10l): Likewise.
	* math/s_clogf.c (__clogf): Likewise.
	* math/s_clogl.c (__clogl): Likewise.
	* math/auto-libm-test-in: Add more tests of clog and clog10.
	* math/auto-libm-test-out: Regenerated.
	* sysdeps/i386/fpu/libm-test-ulps: Update.
	* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
2015-09-28 22:11:22 +00:00
..
bits Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
net Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
netinet Define ETH_ALEN in generic <netinet/if_ether.h>. 2015-03-04 16:11:31 -08:00
nfs Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
sys Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
_G_config.h Remove _G_OPEN64, _G_LSEEK64, _G_MMAP64, _G_FSTAT64 from _G_config.h. 2012-10-18 18:50:43 +00:00
_itoa.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
a.out.h
abort-instr.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
aio_misc.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
allocalim.h
asm-syntax.h
atomic-machine.h Move bits/atomic.h to atomic-machine.h (bug 14912). 2015-09-11 20:00:19 +00:00
c++-types.data Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
confstr.h
device-nrs.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dirstream.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-cache.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-dtprocnum.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-fileid.h Factor file identity rules out of generic rtld code. 2015-07-14 13:15:26 -07:00
dl-fptr.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-hash.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-irel.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-librecon.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-lookupcfg.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-machine.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-osinfo.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-procinfo.c
dl-procinfo.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-sysdep.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
dl-tls.h
dwarf2.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
elide.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
eloop-threshold.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
entry.h
errqueue.h
exit-thread.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
fd_to_filename.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
fips-private.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
fork.h
fpu_control.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
frame.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
framestate.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
gcc-compat.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
gccframe.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
get-rounding-mode.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
gmp-mparam.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
hp-timing-common.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
hp-timing.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
ifreq.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
ifunc-sel.h Move sysdeps/generic/elf/* to sysdeps/generic 2012-03-19 21:04:21 +01:00
intr-msg.h
inttypes.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
ld.abilist Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
ldconfig.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
ldsodefs.h Move bits/libc-lock.h and bits/libc-lockP.h out of bits/ (bug 14912). 2015-09-08 21:11:03 +00:00
libanl.abilist Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
libBrokenLocale.abilist Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
libc-lock.h Move bits/libc-lock.h and bits/libc-lockP.h out of bits/ (bug 14912). 2015-09-08 21:11:03 +00:00
libc-mmap.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
libc-tsd.h Rename bits/libc-tsd.h to libc-tsd.h (bug 14912). 2015-09-03 20:33:46 +00:00
libc.abilist Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
libcidn.abilist Add missed zero length files in previous abilist commit. 2012-04-28 15:38:24 -04:00
libcrypt.abilist Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
libdl.abilist Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
libm-test-ulps
libm.abilist Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
libnss_compat.abilist Add missed zero length files in previous abilist commit. 2012-04-28 15:38:24 -04:00
libnss_db.abilist Add missed zero length files in previous abilist commit. 2012-04-28 15:38:24 -04:00
libnss_dns.abilist Add missed zero length files in previous abilist commit. 2012-04-28 15:38:24 -04:00
libnss_files.abilist Add missed zero length files in previous abilist commit. 2012-04-28 15:38:24 -04:00
libnss_hesiod.abilist Add missed zero length files in previous abilist commit. 2012-04-28 15:38:24 -04:00
libnss_nis.abilist Add missed zero length files in previous abilist commit. 2012-04-28 15:38:24 -04:00
libnss_nisplus.abilist Add missed zero length files in previous abilist commit. 2012-04-28 15:38:24 -04:00
libpthread.abilist Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
libresolv.abilist Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
librt.abilist Add placeholder c++-types.data and *.abilist files. 2015-02-13 15:41:34 -08:00
linkmap.h Rename bits/linkmap.h to linkmap.h (bug 14912). 2015-09-04 19:44:27 +00:00
local-setxid.h
localplt.data Add hidden __tls_get_addr/___tls_get_addr alias 2014-12-21 09:27:11 -08:00
machine-gmon.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
machine-lock.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
machine-sp.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
Makefile Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
malloc-machine.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
malloc-sysdep.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
math_ldbl_opt.h
math_ldbl.h
math_private.h Fix clog, clog10 inaccuracy (bug 19016). 2015-09-28 22:11:22 +00:00
math-tests-arch.h Refactoring of START for conditions in individual tests 2015-05-14 18:07:06 +03:00
math-tests.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
memcopy.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
memusage.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
not-cancel.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
nscd-types.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
pagecopy.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
paths.h generic paths.h: remove old paths from _PATH_STDPATH 2012-11-04 10:11:39 +01:00
profil-counter.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
pty-private.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
register-dump.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
rtld-lowlevel.h
safe-fatal.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
sigcontextinfo.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
siglist.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
sigset-cvt-mask.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
stackguard-macros.h BZ #15754: Fix test case for ARM. 2013-09-23 01:44:38 -04:00
stackinfo.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
stdint.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
stdio-lock.h Move bits/libc-lock.h and bits/libc-lockP.h out of bits/ (bug 14912). 2015-09-08 21:11:03 +00:00
symbol-hacks.h Remove NOT_IN_libc 2014-11-24 15:03:45 +05:30
sysdep-cancel.h
sysdep.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
thread_state.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
tininess.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
tls-macros.h
tls.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
tst-audit.h Move testsuite audit definitions to sysdeps tst-audit.h files. 2012-07-26 11:29:07 +00:00
tst-stack-align.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
unsecvars.h
unwind-dw2-fde-glibc.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
unwind-dw2-fde.c Move bits/libc-lock.h and bits/libc-lockP.h out of bits/ (bug 14912). 2015-09-08 21:11:03 +00:00
unwind-dw2-fde.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
unwind-dw2.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
unwind-pe.c
unwind-pe.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
unwind-resume.h ARM: Consolidate with generic unwinder wrapper code 2015-01-05 15:42:16 -08:00
unwind.h Adjust _Unwind_Word in unwind.h to version in libgcc. 2015-08-26 10:26:26 +02:00
utmp-equal.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00