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authorJoseph Myers <joseph@codesourcery.com>2015-12-09 23:51:11 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-12-09 23:51:11 +0000
commite6a6b1c3de62f3ae3f0e5ac5bdcc49a3342f03e7 (patch)
treea239075b91eca073d80677205d27516017105e63 /sysdeps/ieee754/ldbl-128ibm/e_logl.c
parentf517e06ab71e07b24bf085063b0ba2d072da4a56 (diff)
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Fix ldbl-128ibm logl inaccuracy near 1 (bug 19351).
The ldbl-128ibm implementation of logl is inaccurate for arguments
near 1, because when deciding whether to bypass a series expansion for
log(1+z), where z = x-1, it compares the square of z rather than z
itself with an epsilon value.  This patch fixes that comparison, so
eliminating the test failures for inaccuracy of logl in such cases.

Tested for powerpc.

	[BZ #19351]
	* sysdeps/ieee754/ldbl-128ibm/e_logl.c (__ieee754_logl): When
	expanding log(1+z), compare z rather than its square with epsilon
	to determine when to avoid evaluating the expansion.
Diffstat (limited to 'sysdeps/ieee754/ldbl-128ibm/e_logl.c')
-rw-r--r--sysdeps/ieee754/ldbl-128ibm/e_logl.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/e_logl.c b/sysdeps/ieee754/ldbl-128ibm/e_logl.c
index dcac38062c..14acfc2db7 100644
--- a/sysdeps/ieee754/ldbl-128ibm/e_logl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_logl.c
@@ -270,7 +270,7 @@ __ieee754_logl(long double x)
   /* Series expansion of log(1+z).  */
   w = z * z;
   /* Avoid spurious underflows.  */
-  if (__glibc_unlikely(w <= ldbl_epsilon))
+  if (__glibc_unlikely (fabsl (z) <= ldbl_epsilon))
     y = 0.0L;
   else
     {