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 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
27 * Use is subject to license terms.
28 */
29
30 #include "libm.h"
31
32 /* INDENT OFF */
33 /*
34 * float __k_cos(double x);
35 * kernel (float) cos function on [-pi/4, pi/4], pi/4 ~ 0.785398164
36 * Input x is in double and assumed to be bounded by ~pi/4 in magnitude.
37 *
38 * Method: Let z = x * x, then
39 * C(x) = (C0 + C1*z + C2*z*z) * (C3 + C4*z + z*z)
40 * where
41 * C0 = 1.09349482127188401868272000389539985058873853699e-0003
42 * C1 = -5.03324285989964979398034700054920226866107675091e-0004
43 * C2 = 2.43792880266971107750418061559602239831538067410e-0005
44 * C3 = 9.14499072605666582228127405245558035523741471271e+0002
45 * C4 = -3.63151270591815439197122504991683846785293207730e+0001
46 *
47 * The remez error is bound by |cos(x) - C(x)| < 2**(-34.2)
48 *
49 * Constants:
50 * The hexadecimal values are the intended ones for the following constants.
51 * The decimal values may be used, provided that the compiler will convert
52 * from decimal to binary accurately enough to produce the hexadecimal values
53 * shown.
54 */
55 /* INDENT ON */
56
57 static const double q[] = {
58 /* C0 = */ 1.09349482127188401868272000389539985058873853699e-0003,
59 /* C1 = */ -5.03324285989964979398034700054920226866107675091e-0004,
60 /* C2 = */ 2.43792880266971107750418061559602239831538067410e-0005,
61 /* C3 = */ 9.14499072605666582228127405245558035523741471271e+0002,
62 /* C4 = */ -3.63151270591815439197122504991683846785293207730e+0001,
63 };
64
65 #define C0 q[0]
66 #define C1 q[1]
67 #define C2 q[2]
68 #define C3 q[3]
69 #define C4 q[4]
70
71 float
__k_cosf(double x)72 __k_cosf(double x) {
73 float ft;
74 double z;
75 int hx;
76
77 hx = ((int *) &x)[HIWORD]; /* hx = leading x */
78 if ((hx & ~0x80000000) < 0x3f100000) { /* |x| < 2**-14 */
79 ft = (float) 1;
80 if (((int) x) == 0) /* raise inexact if x != 0 */
81 return (ft);
82 }
83 z = x * x;
84 ft = (float) (((C0 + z * C1) + (z * z) * C2) * (C3 + z * (C4 + z)));
85 return (ft);
86 }
87