Mercurial > hg > CbC > CbC_gcc

annotate libquadmath/math/sqrtq.c @ 158:494b0b89df80 default tip

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author Shinji KONO <kono@ie.u-ryukyu.ac.jp>
date Mon, 25 May 2020 18:13:55 +0900
parents 04ced10e8804
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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1 #include "quadmath-imp.h"
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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2 #include <math.h>
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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3 #include <float.h>
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4
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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5 __float128
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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6 sqrtq (const __float128 x)
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7 {
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8 __float128 y;
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9 int exp;
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10
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11 if (isnanq (x) || (isinfq (x) && x > 0))
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12 return x;
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13
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14 if (x == 0)
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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15 return x;
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16
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17 if (x < 0)
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18 {
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19 /* Return NaN with invalid signal. */
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20 return (x - x) / (x - x);
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21 }
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22
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23 if (x <= DBL_MAX && x >= DBL_MIN)
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24 {
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25 /* Use double result as starting point. */
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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26 y = sqrt ((double) x);
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27
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28 /* Two Newton iterations. */
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29 y -= 0.5q * (y - x / y);
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30 y -= 0.5q * (y - x / y);
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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31 return y;
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32 }
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33
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Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp>
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34 #ifdef HAVE_SQRTL
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35 {
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36 long double xl = (long double) x;
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37 if (xl <= LDBL_MAX && xl >= LDBL_MIN)
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38 {
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39 /* Use long double result as starting point. */
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40 y = (__float128) sqrtl (xl);
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41
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42 /* One Newton iteration. */
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43 y -= 0.5q * (y - x / y);
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44 return y;
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45 }
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46 }
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47 #endif
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48
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49 /* If we're outside of the range of C types, we have to compute
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50 the initial guess the hard way. */
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51 y = frexpq (x, &exp);
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52 if (exp % 2)
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53 y *= 2, exp--;
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54
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55 y = sqrt (y);
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56 y = scalbnq (y, exp / 2);
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57
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58 /* Two Newton iterations. */
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59 y -= 0.5q * (y - x / y);
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60 y -= 0.5q * (y - x / y);
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61 return y;
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62 }
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