GNU C Library master sources branch master updated. glibc-2.22-589-ge6a6b1c

jsm28@sourceware.org jsm28@sourceware.org
Wed Dec 9 23:51:00 GMT 2015


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- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=e6a6b1c3de62f3ae3f0e5ac5bdcc49a3342f03e7

commit e6a6b1c3de62f3ae3f0e5ac5bdcc49a3342f03e7
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Wed Dec 9 23:51:11 2015 +0000

    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.

diff --git a/ChangeLog b/ChangeLog
index 1c7b198..ec8807c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2015-12-09  Joseph Myers  <joseph@codesourcery.com>
 
+	[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.
+
 	[BZ #19350]
 	* sysdeps/ieee754/ldbl-128ibm/e_sinhl.c (__ieee754_sinhl):
 	Increase overflow threshold.
diff --git a/sysdeps/ieee754/ldbl-128ibm/e_logl.c b/sysdeps/ieee754/ldbl-128ibm/e_logl.c
index dcac380..14acfc2 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
     {

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                            |    5 +++++
 sysdeps/ieee754/ldbl-128ibm/e_logl.c |    2 +-
 2 files changed, 6 insertions(+), 1 deletions(-)


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