Fix ldbl-128ibm hypotl internal underflows (bug 14869)

Andreas Jaeger aj@suse.com
Thu Nov 22 06:38:00 GMT 2012


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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