| /* @(#)k_sin.c 5.1 93/09/24 */ | |
| /* | |
| * ==================================================== | |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. | |
| * | |
| * Developed at SunPro, a Sun Microsystems, Inc. business. | |
| * Permission to use, copy, modify, and distribute this | |
| * software is freely granted, provided that this notice | |
| * is preserved. | |
| * ==================================================== | |
| */ | |
| #include <LibConfig.h> | |
| #include <sys/EfiCdefs.h> | |
| #if defined(LIBM_SCCS) && !defined(lint) | |
| __RCSID("$NetBSD: k_sin.c,v 1.11 2002/05/26 22:01:53 wiz Exp $"); | |
| #endif | |
| /* __kernel_sin( x, y, iy) | |
| * kernel sin function on [-pi/4, pi/4], pi/4 ~ 0.7854 | |
| * Input x is assumed to be bounded by ~pi/4 in magnitude. | |
| * Input y is the tail of x. | |
| * Input iy indicates whether y is 0. (if iy=0, y assume to be 0). | |
| * | |
| * Algorithm | |
| * 1. Since sin(-x) = -sin(x), we need only to consider positive x. | |
| * 2. if x < 2^-27 (hx<0x3e400000 0), return x with inexact if x!=0. | |
| * 3. sin(x) is approximated by a polynomial of degree 13 on | |
| * [0,pi/4] | |
| * 3 13 | |
| * sin(x) ~ x + S1*x + ... + S6*x | |
| * where | |
| * | |
| * |sin(x) 2 4 6 8 10 12 | -58 | |
| * |----- - (1+S1*x +S2*x +S3*x +S4*x +S5*x +S6*x )| <= 2 | |
| * | x | | |
| * | |
| * 4. sin(x+y) = sin(x) + sin'(x')*y | |
| * ~ sin(x) + (1-x*x/2)*y | |
| * For better accuracy, let | |
| * 3 2 2 2 2 | |
| * r = x *(S2+x *(S3+x *(S4+x *(S5+x *S6)))) | |
| * then 3 2 | |
| * sin(x) = x + (S1*x + (x *(r-y/2)+y)) | |
| */ | |
| #include "math.h" | |
| #include "math_private.h" | |
| static const double | |
| half = 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */ | |
| S1 = -1.66666666666666324348e-01, /* 0xBFC55555, 0x55555549 */ | |
| S2 = 8.33333333332248946124e-03, /* 0x3F811111, 0x1110F8A6 */ | |
| S3 = -1.98412698298579493134e-04, /* 0xBF2A01A0, 0x19C161D5 */ | |
| S4 = 2.75573137070700676789e-06, /* 0x3EC71DE3, 0x57B1FE7D */ | |
| S5 = -2.50507602534068634195e-08, /* 0xBE5AE5E6, 0x8A2B9CEB */ | |
| S6 = 1.58969099521155010221e-10; /* 0x3DE5D93A, 0x5ACFD57C */ | |
| double | |
| __kernel_sin(double x, double y, int iy) | |
| { | |
| double z,r,v; | |
| int32_t ix; | |
| GET_HIGH_WORD(ix,x); | |
| ix &= 0x7fffffff; /* high word of x */ | |
| if(ix<0x3e400000) /* |x| < 2**-27 */ | |
| {if((int)x==0) return x;} /* generate inexact */ | |
| z = x*x; | |
| v = z*x; | |
| r = S2+z*(S3+z*(S4+z*(S5+z*S6))); | |
| if(iy==0) return x+v*(S1+z*r); | |
| else return x-((z*(half*y-v*r)-y)-v*S1); | |
| } |