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Fixed the approximation to pio4. pio4_hi must be pio2_hi/2 since it

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shares its low half with pio2_hi.  pio2_hi is rounded down although
rounding to nearest would be a tiny bit better, so pio4_hi must be
rounded down too.  It was rounded to nearest, which happens to be
different in float precision but the same in double precision.

This fixes about 13.5 million errors of more than 1 ulp in asinf().
The largest error was 2.81 ulps on amd64 and 2.57 ulps on i386 -O1.
Now the largest error is 0.93 ulps on amd65 and 0.67 ulps on i386 -O1.
This commit is contained in:
Bruce Evans 2005-12-04 13:52:46 +00:00
parent 2a40d89ff4
commit 0f06be5a4d
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=153088
1 changed files with 1 additions and 1 deletions
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2
lib/msun/src/e_asinf.c
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@ -25,7 +25,7 @@ one = 1.0000000000e+00, /* 0x3F800000 */
huge = 1.000e+30,
pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
pio4_hi = 7.8539818525e-01, /* 0x3f490fdb */
pio4_hi = 7.8539812565e-01, /* 0x3f490fda */
/* coefficient for R(x^2) */
pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
pS1 = -3.2556581497e-01, /* 0xbea6b090 */