s_atanf.c revision 176451
12116Sjkh/* s_atanf.c -- float version of s_atan.c. 22116Sjkh * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 32116Sjkh */ 42116Sjkh 52116Sjkh/* 62116Sjkh * ==================================================== 72116Sjkh * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 82116Sjkh * 92116Sjkh * Developed at SunPro, a Sun Microsystems, Inc. business. 102116Sjkh * Permission to use, copy, modify, and distribute this 118870Srgrimes * software is freely granted, provided that this notice 122116Sjkh * is preserved. 132116Sjkh * ==================================================== 142116Sjkh */ 152116Sjkh 16176451Sdas#include <sys/cdefs.h> 17176451Sdas__FBSDID("$FreeBSD: head/lib/msun/src/s_atanf.c 176451 2008-02-22 02:30:36Z das $"); 182116Sjkh 192116Sjkh#include "math.h" 202116Sjkh#include "math_private.h" 212116Sjkh 222116Sjkhstatic const float atanhi[] = { 232116Sjkh 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */ 242116Sjkh 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */ 252116Sjkh 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */ 262116Sjkh 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */ 272116Sjkh}; 282116Sjkh 292116Sjkhstatic const float atanlo[] = { 302116Sjkh 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */ 312116Sjkh 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */ 322116Sjkh 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */ 332116Sjkh 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */ 342116Sjkh}; 352116Sjkh 362116Sjkhstatic const float aT[] = { 372116Sjkh 3.3333334327e-01, /* 0x3eaaaaaa */ 382116Sjkh -2.0000000298e-01, /* 0xbe4ccccd */ 392116Sjkh 1.4285714924e-01, /* 0x3e124925 */ 402116Sjkh -1.1111110449e-01, /* 0xbde38e38 */ 412116Sjkh 9.0908870101e-02, /* 0x3dba2e6e */ 422116Sjkh -7.6918758452e-02, /* 0xbd9d8795 */ 432116Sjkh 6.6610731184e-02, /* 0x3d886b35 */ 442116Sjkh -5.8335702866e-02, /* 0xbd6ef16b */ 452116Sjkh 4.9768779427e-02, /* 0x3d4bda59 */ 462116Sjkh -3.6531571299e-02, /* 0xbd15a221 */ 472116Sjkh 1.6285819933e-02, /* 0x3c8569d7 */ 482116Sjkh}; 492116Sjkh 508870Srgrimes static const float 512116Sjkhone = 1.0, 522116Sjkhhuge = 1.0e30; 532116Sjkh 5497413Salfredfloat 5597413Salfredatanf(float x) 562116Sjkh{ 572116Sjkh float w,s1,s2,z; 582116Sjkh int32_t ix,hx,id; 592116Sjkh 602116Sjkh GET_FLOAT_WORD(hx,x); 612116Sjkh ix = hx&0x7fffffff; 622116Sjkh if(ix>=0x50800000) { /* if |x| >= 2^34 */ 632116Sjkh if(ix>0x7f800000) 642116Sjkh return x+x; /* NaN */ 652116Sjkh if(hx>0) return atanhi[3]+atanlo[3]; 662116Sjkh else return -atanhi[3]-atanlo[3]; 672116Sjkh } if (ix < 0x3ee00000) { /* |x| < 0.4375 */ 682116Sjkh if (ix < 0x31000000) { /* |x| < 2^-29 */ 692116Sjkh if(huge+x>one) return x; /* raise inexact */ 702116Sjkh } 712116Sjkh id = -1; 722116Sjkh } else { 732116Sjkh x = fabsf(x); 742116Sjkh if (ix < 0x3f980000) { /* |x| < 1.1875 */ 752116Sjkh if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */ 768870Srgrimes id = 0; x = ((float)2.0*x-one)/((float)2.0+x); 772116Sjkh } else { /* 11/16<=|x|< 19/16 */ 788870Srgrimes id = 1; x = (x-one)/(x+one); 792116Sjkh } 802116Sjkh } else { 812116Sjkh if (ix < 0x401c0000) { /* |x| < 2.4375 */ 822116Sjkh id = 2; x = (x-(float)1.5)/(one+(float)1.5*x); 832116Sjkh } else { /* 2.4375 <= |x| < 2^66 */ 842116Sjkh id = 3; x = -(float)1.0/x; 852116Sjkh } 862116Sjkh }} 872116Sjkh /* end of argument reduction */ 882116Sjkh z = x*x; 892116Sjkh w = z*z; 902116Sjkh /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */ 912116Sjkh s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10]))))); 922116Sjkh s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9])))); 932116Sjkh if (id<0) return x - x*(s1+s2); 942116Sjkh else { 952116Sjkh z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x); 962116Sjkh return (hx<0)? -z:z; 972116Sjkh } 982116Sjkh} 99