1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
24 */
25
26 /*
27 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
28 * Use is subject to license terms.
29 */
30
31 /* BEGIN CSTYLED */
32 /*
33 * __k_cosl(long double x, long double y)
34 * kernel cos function on [-pi/4, pi/4], pi/4 ~ 0.785398164
35 * Input x is assumed to be bounded by ~pi/4 in magnitude.
36 * Input y is the tail of x.
37 *
38 * Table look up algorithm
39 * 1. by cos(-x) = cos(x), we may replace x by |x|
40 * 2. if x < 25/128 = [0x3ffc4000, 0] = 0.15625 , then
41 * if x < 2^-57 (hx < 0x3fc60000 0), return 1.0 with inexact if x != 0
42 * z = x*x;
43 * if x <= 1/128 = 2**-7 = 0.0078125
44 * cos(x)=1.0+z*(qq1+z*(qq2+z*(qq3+z*(qq4+z*qq5))))
45 * else
46 * cos(x)=1.0+z*(q1+ ... z*q8)
47 * 3. else
48 * ht = (hx + 0x400)&0x7ffff800 (round x to a break point t)
49 * lt = 0
50 * i = (hy-0x3ffc4000)>>11; (i<=64)
51 * x' = (x - t)+y (|x'| ~<= 2^-7
52 * By
53 * cos(t+x')
54 * = cos(t)cos(x')-sin(t)sin(x')
55 * = cos(t)(1+z*(qq1+z*qq2))-[sin(t)]*x*(1+z*(pp1+z*pp2))
56 * = cos(t) + [cos(t)]*(z*(qq1+z*qq2))-
57 * [sin(t)]*x*(1+z*(pp1+z*pp2))
58 *
59 * Thus,
60 * let a= _TBL_cos_hi[i], b = _TBL_cos_lo[i], c= _TBL_sin_hi[i],
61 * x = (x-t)+y
62 * z = x*x;
63 * cos(t+x) = a+(b+ (-c*x*(1+z*(pp1+z*pp2))+a*(z*(qq1+z*qq2)))
64 */
65 /* END CSTYLED */
66
67 #include "libm.h"
68
69 extern const long double _TBL_cosl_hi[], _TBL_cosl_lo[], _TBL_sinl_hi[];
70 static const long double one = 1.0L;
71
72 /*
73 * 3 11 -122.32
74 * |sin(x) - (x+pp1*x +...+ pp5*x )| <= 2 for |x|<1/64
75 */
76 static const long double
77 pp1 = -1.666666666666666666666666666586782940810e-0001L,
78 pp2 = +8.333333333333333333333003723660929317540e-0003L,
79 pp3 = -1.984126984126984076045903483778337804470e-0004L,
80 pp4 = +2.755731922361906641319723106210900949413e-0006L,
81 pp5 = -2.505198398570947019093998469135012057673e-0008L;
82
83 /*
84 * 2 16 -117.11
85 * |cos(x) - (1+q1*x + ... + q8*x )| <= 2 for |x|<= 0.15625
86 */
87 static const long double
88 q1 = -4.999999999999999999999999999999756416975e-0001L,
89 q2 = +4.166666666666666666666666664006066577258e-0002L,
90 q3 = -1.388888888888888888888877700363937169637e-0003L,
91 q4 = +2.480158730158730158494468463031814083559e-0005L,
92 q5 = -2.755731922398586276322819250356005542871e-0007L,
93 q6 = +2.087675698767424261441959760729854017855e-0009L,
94 q7 = -1.147074481239662089072452129010790774761e-0011L,
95 q8 = +4.777761647399651599730663422263531034782e-0014L;
96
97 /*
98 * 2 10 -123.84
99 * |cos(x) - (1+qq1*x +...+ qq5*x )| <= 2 for |x|<=1/128
100 */
101 static const long double
102 qq1 = -4.999999999999999999999999999999378373641e-0001L,
103 qq2 = +4.166666666666666666666665478399327703130e-0002L,
104 qq3 = -1.388888888888888888058211230618051613494e-0003L,
105 qq4 = +2.480158730156105377771585658905303111866e-0005L,
106 qq5 = -2.755728099762526325736488376695157008736e-0007L;
107
108 #define i0 0
109
110 long double
111 __k_cosl(long double x, long double y)
112 {
113 long double a, t, z, w;
114 int *pt = (int *)&t, *px = (int *)&x;
115 int i, j, hx, ix;
116
117 t = 1.0L;
118 hx = px[i0];
119 ix = hx & 0x7fffffff;
120
121 if (ix < 0x3ffc4000) {
122 if (ix < 0x3fc60000)
123 if ((i = (int)x) == 0)
124 return (one);
125
126 /* generate inexact */
127 z = x * x;
128
129 if (ix < 0x3ff80000) { /* 0.0078125 */
130 return (one + z * (qq1 + z * (qq2 + z * (qq3 + z *
131 (qq4 + z * qq5)))));
132 } else {
133 return (one + z * (q1 + z * (q2 + z * (q3 + z * (q4 +
134 z * (q5 + z * (q6 + z * (q7 + z * q8))))))));
135 }
136 }
137
138 j = (ix + 0x400) & 0x7ffff800;
139 i = (j - 0x3ffc4000) >> 11;
140 pt[i0] = j;
141
142 if (hx > 0)
143 x = y - (t - x);
144 else
145 x = (-y) - (t + x);
146
147 a = _TBL_cosl_hi[i];
148 z = x * x;
149 t = z * (qq1 + z * (qq2 + z * (qq3 + z * (qq4 + z * qq5))));
150 w = x * (one + z * (pp1 + z * (pp2 + z * (pp3 + z * (pp4 + z * pp5)))));
151 t = _TBL_cosl_lo[i] - (_TBL_sinl_hi[i] * w - a * t);
152 return (a + t);
153 }