ipiq: Add simple IPI latency measure sysctls (2)
[dragonfly.git] / lib / libm / src / k_tanf.c
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1/* k_tanf.c -- float version of k_tan.c
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
1a3b704c 3 * Optimized by Bruce D. Evans.
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4 */
5
6/*
7 * ====================================================
1a3b704c 8 * Copyright 2004 Sun Microsystems, Inc. All Rights Reserved.
b34b60bc 9 *
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10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
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14 *
15 * $FreeBSD: head/lib/msun/src/k_tanf.c 239192 2012-08-11 11:13:48Z dim $
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16 */
17
6ff43c94 18#include "math.h"
b34b60bc 19#include "math_private.h"
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20
21/* |tan(x)/x - t(x)| < 2**-25.5 (~[-2e-08, 2e-08]). */
22static const double
b34b60bc 23T[] = {
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24 0x15554d3418c99f.0p-54, /* 0.333331395030791399758 */
25 0x1112fd38999f72.0p-55, /* 0.133392002712976742718 */
26 0x1b54c91d865afe.0p-57, /* 0.0533812378445670393523 */
27 0x191df3908c33ce.0p-58, /* 0.0245283181166547278873 */
28 0x185dadfcecf44e.0p-61, /* 0.00297435743359967304927 */
29 0x1362b9bf971bcd.0p-59, /* 0.00946564784943673166728 */
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30};
31
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32#ifdef INLINE_KERNEL_TANDF
33static __inline
34#endif
35float
1a3b704c 36__kernel_tandf(double x, int iy)
b34b60bc 37{
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38 double z,r,w,s,t,u;
39
b34b60bc 40 z = x*x;
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41 /*
42 * Split up the polynomial into small independent terms to give
43 * opportunities for parallel evaluation. The chosen splitting is
44 * micro-optimized for Athlons (XP, X64). It costs 2 multiplications
45 * relative to Horner's method on sequential machines.
46 *
47 * We add the small terms from lowest degree up for efficiency on
48 * non-sequential machines (the lowest degree terms tend to be ready
49 * earlier). Apart from this, we don't care about order of
50 * operations, and don't need to to care since we have precision to
51 * spare. However, the chosen splitting is good for accuracy too,
52 * and would give results as accurate as Horner's method if the
53 * small terms were added from highest degree down.
54 */
55 r = T[4]+z*T[5];
56 t = T[2]+z*T[3];
57 w = z*z;
b34b60bc 58 s = z*x;
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59 u = T[0]+z*T[1];
60 r = (x+s*u)+(s*w)*(t+w*r);
61 if(iy==1) return r;
62 else return -1.0/r;
b34b60bc 63}