diff options
Diffstat (limited to 'sysdeps/libm-ieee754/k_sin.c')
| -rw-r--r-- | sysdeps/libm-ieee754/k_sin.c | 46 |
1 files changed, 29 insertions, 17 deletions
diff --git a/sysdeps/libm-ieee754/k_sin.c b/sysdeps/libm-ieee754/k_sin.c index 86b95529bc..49c59228e0 100644 --- a/sysdeps/libm-ieee754/k_sin.c +++ b/sysdeps/libm-ieee754/k_sin.c @@ -5,10 +5,13 @@ * * Developed at SunPro, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this - * software is freely granted, provided that this notice + * software is freely granted, provided that this notice * is preserved. * ==================================================== */ +/* Modified by Naohiko Shimizu/Tokai University, Japan 1997/08/25, + for performance improvement on pipelined processors. +*/ #if defined(LIBM_SCCS) && !defined(lint) static char rcsid[] = "$NetBSD: k_sin.c,v 1.8 1995/05/10 20:46:31 jtc Exp $"; @@ -18,24 +21,24 @@ static char rcsid[] = "$NetBSD: k_sin.c,v 1.8 1995/05/10 20:46:31 jtc Exp $"; * kernel sin function on [-pi/4, pi/4], pi/4 ~ 0.7854 * Input x is assumed to be bounded by ~pi/4 in magnitude. * Input y is the tail of x. - * Input iy indicates whether y is 0. (if iy=0, y assume to be 0). + * Input iy indicates whether y is 0. (if iy=0, y assume to be 0). * * Algorithm - * 1. Since sin(-x) = -sin(x), we need only to consider positive x. + * 1. Since sin(-x) = -sin(x), we need only to consider positive x. * 2. if x < 2^-27 (hx<0x3e400000 0), return x with inexact if x!=0. * 3. sin(x) is approximated by a polynomial of degree 13 on * [0,pi/4] * 3 13 * sin(x) ~ x + S1*x + ... + S6*x * where - * + * * |sin(x) 2 4 6 8 10 12 | -58 * |----- - (1+S1*x +S2*x +S3*x +S4*x +S5*x +S6*x )| <= 2 - * | x | - * + * | x | + * * 4. sin(x+y) = sin(x) + sin'(x')*y * ~ sin(x) + (1-x*x/2)*y - * For better accuracy, let + * For better accuracy, let * 3 2 2 2 2 * r = x *(S2+x *(S3+x *(S4+x *(S5+x *S6)))) * then 3 2 @@ -46,17 +49,18 @@ static char rcsid[] = "$NetBSD: k_sin.c,v 1.8 1995/05/10 20:46:31 jtc Exp $"; #include "math_private.h" #ifdef __STDC__ -static const double +static const double #else -static double +static double #endif -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 */ +S[] = { + 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */ + -1.66666666666666324348e-01, /* 0xBFC55555, 0x55555549 */ + 8.33333333332248946124e-03, /* 0x3F811111, 0x1110F8A6 */ + -1.98412698298579493134e-04, /* 0xBF2A01A0, 0x19C161D5 */ + 2.75573137070700676789e-06, /* 0x3EC71DE3, 0x57B1FE7D */ + -2.50507602534068634195e-08, /* 0xBE5AE5E6, 0x8A2B9CEB */ + 1.58969099521155010221e-10}; /* 0x3DE5D93A, 0x5ACFD57C */ #ifdef __STDC__ double __kernel_sin(double x, double y, int iy) @@ -65,7 +69,7 @@ S6 = 1.58969099521155010221e-10; /* 0x3DE5D93A, 0x5ACFD57C */ double x,y; int iy; /* iy=0 if y is zero */ #endif { - double z,r,v; + double z,r,v,z1,r1,r2; int32_t ix; GET_HIGH_WORD(ix,x); ix &= 0x7fffffff; /* high word of x */ @@ -73,7 +77,15 @@ S6 = 1.58969099521155010221e-10; /* 0x3DE5D93A, 0x5ACFD57C */ {if((int)x==0) return x;} /* generate inexact */ z = x*x; v = z*x; +#ifdef DO_NOT_USE_THIS 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); +#else + r1 = S[5]+z*S[6]; z1 = z*z*z; + r2 = S[3]+z*S[4]; + r = S[2] + z*r2 + z1*r1; + if(iy==0) return x+v*(S[1]+z*r); + else return x-((z*(S[0]*y-v*r)-y)-v*S[1]); +#endif } |