diff options
Diffstat (limited to 'sysdeps/ieee754/dbl-64/k_tan.c')
| -rw-r--r-- | sysdeps/ieee754/dbl-64/k_tan.c | 137 |
1 files changed, 1 insertions, 136 deletions
diff --git a/sysdeps/ieee754/dbl-64/k_tan.c b/sysdeps/ieee754/dbl-64/k_tan.c index 7ef4103bc9..cc5c205a5f 100644 --- a/sysdeps/ieee754/dbl-64/k_tan.c +++ b/sysdeps/ieee754/dbl-64/k_tan.c @@ -1,136 +1 @@ -/* @(#)k_tan.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. - * ==================================================== - */ -/* 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_tan.c,v 1.8 1995/05/10 20:46:37 jtc Exp $"; -#endif - -/* __kernel_tan( x, y, k ) - * kernel tan 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 k indicates whether tan (if k=1) or - * -1/tan (if k= -1) is returned. - * - * Algorithm - * 1. Since tan(-x) = -tan(x), we need only to consider positive x. - * 2. if x < 2^-28 (hx<0x3e300000 0), return x with inexact if x!=0. - * 3. tan(x) is approximated by a odd polynomial of degree 27 on - * [0,0.67434] - * 3 27 - * tan(x) ~ x + T1*x + ... + T13*x - * where - * - * |tan(x) 2 4 26 | -59.2 - * |----- - (1+T1*x +T2*x +.... +T13*x )| <= 2 - * | x | - * - * Note: tan(x+y) = tan(x) + tan'(x)*y - * ~ tan(x) + (1+x*x)*y - * Therefore, for better accuracy in computing tan(x+y), let - * 3 2 2 2 2 - * r = x *(T2+x *(T3+x *(...+x *(T12+x *T13)))) - * then - * 3 2 - * tan(x+y) = x + (T1*x + (x *(r+y)+y)) - * - * 4. For x in [0.67434,pi/4], let y = pi/4 - x, then - * tan(x) = tan(pi/4-y) = (1-tan(y))/(1+tan(y)) - * = 1 - 2*(tan(y) - (tan(y)^2)/(1+tan(y))) - */ - -#include "math.h" -#include "math_private.h" -static const double -one = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */ -pio4 = 7.85398163397448278999e-01, /* 0x3FE921FB, 0x54442D18 */ -pio4lo= 3.06161699786838301793e-17, /* 0x3C81A626, 0x33145C07 */ -T[] = { - 3.33333333333334091986e-01, /* 0x3FD55555, 0x55555563 */ - 1.33333333333201242699e-01, /* 0x3FC11111, 0x1110FE7A */ - 5.39682539762260521377e-02, /* 0x3FABA1BA, 0x1BB341FE */ - 2.18694882948595424599e-02, /* 0x3F9664F4, 0x8406D637 */ - 8.86323982359930005737e-03, /* 0x3F8226E3, 0xE96E8493 */ - 3.59207910759131235356e-03, /* 0x3F6D6D22, 0xC9560328 */ - 1.45620945432529025516e-03, /* 0x3F57DBC8, 0xFEE08315 */ - 5.88041240820264096874e-04, /* 0x3F4344D8, 0xF2F26501 */ - 2.46463134818469906812e-04, /* 0x3F3026F7, 0x1A8D1068 */ - 7.81794442939557092300e-05, /* 0x3F147E88, 0xA03792A6 */ - 7.14072491382608190305e-05, /* 0x3F12B80F, 0x32F0A7E9 */ - -1.85586374855275456654e-05, /* 0xBEF375CB, 0xDB605373 */ - 2.59073051863633712884e-05, /* 0x3EFB2A70, 0x74BF7AD4 */ -}; - -double __kernel_tan(double x, double y, int iy) -{ - double z,r,v,w,s,r1,r2,r3,v1,v2,v3,w2,w4; - int32_t ix,hx; - GET_HIGH_WORD(hx,x); - ix = hx&0x7fffffff; /* high word of |x| */ - if(ix<0x3e300000) /* x < 2**-28 */ - {if((int)x==0) { /* generate inexact */ - u_int32_t low; - GET_LOW_WORD(low,x); - if(((ix|low)|(iy+1))==0) return one/fabs(x); - else return (iy==1)? x: -one/x; - } - } - if(ix>=0x3FE59428) { /* |x|>=0.6744 */ - if(hx<0) {x = -x; y = -y;} - z = pio4-x; - w = pio4lo-y; - x = z+w; y = 0.0; - } - z = x*x; - w = z*z; - /* Break x^5*(T[1]+x^2*T[2]+...) into - * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) + - * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12])) - */ -#ifdef DO_NOT_USE_THIS - r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11])))); - v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12]))))); -#else - v1 = T[10]+w*T[12]; w2=w*w; - v2 = T[6]+w*T[8]; w4=w2*w2; - v3 = T[2]+w*T[4]; v1=z*v1; - r1 = T[9]+w*T[11]; v2=z*v2; - r2 = T[5]+w*T[7]; v3=z*v3; - r3 = T[1]+w*T[3]; - v = v3 + w2*v2 + w4*v1; - r = r3 + w2*r2 + w4*r1; -#endif - s = z*x; - r = y + z*(s*(r+v)+y); - r += T[0]*s; - w = x+r; - if(ix>=0x3FE59428) { - v = (double)iy; - return (double)(1-((hx>>30)&2))*(v-2.0*(x-(w*w/(w+v)-r))); - } - if(iy==1) return w; - else { /* if allow error up to 2 ulp, - simply return -1.0/(x+r) here */ - /* compute -1.0/(x+r) accurately */ - double a,t; - z = w; - SET_LOW_WORD(z,0); - v = r-(z - x); /* z+v = r+x */ - t = a = -1.0/w; /* a = -1.0/w */ - SET_LOW_WORD(t,0); - s = 1.0+t*z; - return t+a*(s+t*v); - } -} +/* Not needed anymore. */ |