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1 /* s_atanhl.c -- __float128 version of s_atan.c.
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2 * Conversion to __float128 by Ulrich Drepper,
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3 * Cygnus Support, drepper@cygnus.com.
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4 */
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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5
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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6 /*
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7 * ====================================================
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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9 *
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10 * Developed at SunPro, a Sun Microsystems, Inc. business.
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11 * Permission to use, copy, modify, and distribute this
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12 * software is freely granted, provided that this notice
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13 * is preserved.
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14 * ====================================================
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15 */
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16
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111
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17 /* atanhq(x)
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18 * Method :
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19 * 1.Reduced x to positive by atanh(-x) = -atanh(x)
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20 * 2.For x>=0.5
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21 * 1 2x x
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22 * atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
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23 * 2 1 - x 1 - x
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24 *
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25 * For x<0.5
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26 * atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x))
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27 *
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28 * Special cases:
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29 * atanhl(x) is NaN if |x| > 1 with signal;
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30 * atanhl(NaN) is that NaN with no signal;
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31 * atanhl(+-1) is +-INF with signal.
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32 *
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33 */
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34
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35 #include "quadmath-imp.h"
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36
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37 static const __float128 one = 1.0Q, huge = 1e4900Q;
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38 static const __float128 zero = 0.0Q;
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39
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40 __float128
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41 atanhq (__float128 x)
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42 {
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43 __float128 t;
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44 uint32_t jx, ix;
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45 ieee854_float128 u;
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46
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47 u.value = x;
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48 jx = u.words32.w0;
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49 ix = jx & 0x7fffffff;
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50 u.words32.w0 = ix;
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51 if (ix >= 0x3fff0000) /* |x| >= 1.0 or infinity or NaN */
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52 {
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53 if (u.value == one)
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54 return x/zero;
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55 else
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56 return (x-x)/(x-x);
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57 }
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111
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58 if(ix<0x3fc60000 && (huge+x)>zero) /* x < 2^-57 */
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59 {
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60 math_check_force_underflow (x);
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61 return x;
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62 }
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63
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64 if(ix<0x3ffe0000) { /* x < 0.5 */
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65 t = u.value+u.value;
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66 t = 0.5*log1pq(t+t*u.value/(one-u.value));
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67 } else
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68 t = 0.5*log1pq((u.value+u.value)/(one-u.value));
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69 if(jx & 0x80000000) return -t; else return t;
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70 }
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