usr/src/lib/libm/common/R/__sinf.c

   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_sin(double x);
  35  * kernel (float) sin 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  *      S(x) = x(S0 + S1*z)(S2 + S3*z + z*z)
  40  * where
  41  *      S0 =   1.85735322054308378716204874632872525989806770558e-0003,
  42  *      S1 =  -1.95035094218403635082921458859320791358115801259e-0004,
  43  *      S2 =   5.38400550766074785970952495168558701485841707252e+0002,
  44  *      S3 =  -3.31975110777873728964197739157371509422022905947e+0001,
  45  *
  46  * The remez error is bound by  |(sin(x) - S(x))/x| < 2**(-28.2)
  47  *
  48  * Constants:
  49  * The hexadecimal values are the intended ones for the following constants.
  50  * The decimal values may be used, provided that the compiler will convert
  51  * from decimal to binary accurately enough to produce the hexadecimal values
  52  * shown.
  53  */
  54 /* INDENT ON */
  55
  56 static const double q[] = {
  57 /* S0 = */  1.85735322054308378716204874632872525989806770558e-0003,
  58 /* S1 = */ -1.95035094218403635082921458859320791358115801259e-0004,
  59 /* S2 = */  5.38400550766074785970952495168558701485841707252e+0002,
  60 /* S3 = */ -3.31975110777873728964197739157371509422022905947e+0001,
  61 };
  62
  63 #define S0  q[0]
  64 #define S1  q[1]
  65 #define S2  q[2]
  66 #define S3  q[3]
  67
  68 float
  69 __k_sinf(double x) {
  70         float ft;
  71         double z;
  72         int hx;
  73
  74         hx = ((int *) &x)[HIWORD];      /* hx = leading x */
  75         if ((hx & ~0x80000000) < 0x3f100000) {  /* if |x| < 2**-14 */
  76                 ft = (float) x;
  77                 if ((int) x == 0)       /* raise inexact if x != 0 */
  78                         return (ft);
  79         }
  80         z = x * x;
  81         ft = (float) ((x * (S0 + z * S1)) * (S2 + z * (S3 + z)));
  82         return (ft);
  83 }