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Re: Fix ldbl-128ibm hypotl internal underflows (bug 14869)
- From: Andreas Jaeger <aj at suse dot com>
- To: "Joseph S. Myers" <joseph at codesourcery dot com>
- Cc: libc-alpha at sourceware dot org
- Date: Thu, 22 Nov 2012 07:38:44 +0100
- Subject: Re: Fix ldbl-128ibm hypotl internal underflows (bug 14869)
- References: <Pine.LNX.4.64.1211220218410.11924@digraph.polyomino.org.uk>
On 11/22/2012 03:19 AM, Joseph S. Myers wrote:
Bug 14869 is inaccuracy and spurious underflows from ldbl128-ibm
hypotl for arguments above 2**-500, but not large enough to avoid
underflow when squaring (the 2**-500 value being unchanged from the
dbl-64 version). This patch (relative to a tree with my fix for bug
14868 applied) fixes this by using 2**-450 instead as the threshold
for scaling up.
Tested that this fixes the large errors for the added test on powerpc.
2012-11-22 Joseph Myers <joseph@codesourcery.com>
[BZ #14869]
* sysdeps/ieee754/ldbl-128ibm/e_hypotl.c (__ieee754_hypotl): Scale
up arguments below 2**-450, not just those below 2**-500.
* math/libm-test.inc (hypot_test): Add another test.
Thanks, this is fine,
Andreas
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