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137 lines
4.4 KiB
C
137 lines
4.4 KiB
C
/*
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* $Id: math_atanf.c,v 1.3 2006-01-08 12:04:23 obarthel Exp $
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*
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* :ts=4
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*
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* Portable ISO 'C' (1994) runtime library for the Amiga computer
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* Copyright (c) 2002-2015 by Olaf Barthel <obarthel (at) gmx.net>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Neither the name of Olaf Barthel nor the names of contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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*
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* PowerPC math library based in part on work by Sun Microsystems
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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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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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*/
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#ifndef _MATH_HEADERS_H
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#include "math_headers.h"
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#endif /* _MATH_HEADERS_H */
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/****************************************************************************/
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#if defined(FLOATING_POINT_SUPPORT)
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/****************************************************************************/
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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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LONG 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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/****************************************************************************/
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#endif /* FLOATING_POINT_SUPPORT */
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