5980be9b3c
This work is based in part on code from NetBSD libm, libc and kernel. The library is partly public domain and partly BSD-style licensed.
101 lines
2.8 KiB
C
101 lines
2.8 KiB
C
/* s_atanf.c -- float version of s_atan.c.
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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#include <sys/cdefs.h>
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#if defined(LIBM_SCCS) && !defined(lint)
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__RCSID("$NetBSD: s_atanf.c,v 1.7 2002/05/26 22:01:54 wiz Exp $");
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#endif
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#include "math.h"
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#include "math_private.h"
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static const float atanhi[] = {
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4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
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7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
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9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
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1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
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};
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static const float atanlo[] = {
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5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
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3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
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3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
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7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
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};
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static const float aT[] = {
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3.3333334327e-01, /* 0x3eaaaaaa */
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-2.0000000298e-01, /* 0xbe4ccccd */
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1.4285714924e-01, /* 0x3e124925 */
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-1.1111110449e-01, /* 0xbde38e38 */
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9.0908870101e-02, /* 0x3dba2e6e */
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-7.6918758452e-02, /* 0xbd9d8795 */
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6.6610731184e-02, /* 0x3d886b35 */
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-5.8335702866e-02, /* 0xbd6ef16b */
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4.9768779427e-02, /* 0x3d4bda59 */
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-3.6531571299e-02, /* 0xbd15a221 */
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1.6285819933e-02, /* 0x3c8569d7 */
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};
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static const float
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one = 1.0,
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huge = 1.0e30;
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float
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atanf(float x)
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{
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float w,s1,s2,z;
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int32_t ix,hx,id;
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GET_FLOAT_WORD(hx,x);
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ix = hx&0x7fffffff;
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if(ix>=0x50800000) { /* if |x| >= 2^34 */
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if(ix>0x7f800000)
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return x+x; /* NaN */
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if(hx>0) return atanhi[3]+atanlo[3];
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else return -atanhi[3]-atanlo[3];
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} if (ix < 0x3ee00000) { /* |x| < 0.4375 */
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if (ix < 0x31000000) { /* |x| < 2^-29 */
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if(huge+x>one) return x; /* raise inexact */
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}
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id = -1;
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} else {
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x = fabsf(x);
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if (ix < 0x3f980000) { /* |x| < 1.1875 */
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if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */
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id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
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} else { /* 11/16<=|x|< 19/16 */
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id = 1; x = (x-one)/(x+one);
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}
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} else {
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if (ix < 0x401c0000) { /* |x| < 2.4375 */
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id = 2; x = (x-(float)1.5)/(one+(float)1.5*x);
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} else { /* 2.4375 <= |x| < 2^66 */
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id = 3; x = -(float)1.0/x;
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}
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}}
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/* end of argument reduction */
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z = x*x;
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w = z*z;
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/* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
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s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10])))));
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s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9]))));
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if (id<0) return x - x*(s1+s2);
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else {
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z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
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return (hx<0)? -z:z;
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}
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}
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