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[/] [or1k/] [trunk/] [newlib/] [newlib/] [libm/] [math/] [sf_atan.c] - Blame information for rev 1767

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1 39 lampret 
/* sf_atan.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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 */
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#include "fdlibm.h"
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#ifdef __STDC__
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static const float atanhi[] = {
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#else
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static float atanhi[] = {
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#endif
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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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#ifdef __STDC__
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static const float atanlo[] = {
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#else
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static float atanlo[] = {
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#endif
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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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#ifdef __STDC__
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static const float aT[] = {
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#else
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static float aT[] = {
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#endif
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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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#ifdef __STDC__
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        static const float
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#else
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        static float
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#endif
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one   = 1.0,
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huge   = 1.0e30;
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#ifdef __STDC__
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        float atanf(float x)
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#else
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        float atanf(x)
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        float x;
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#endif
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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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#ifdef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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        double atan(double x)
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#else
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        double atan(x)
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        double x;
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#endif
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{
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        return (double) atanf((float) x);
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */

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