1 | |
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2 | /* @(#)e_remainder.c 5.1 93/09/24 */ |
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3 | /* |
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4 | * ==================================================== |
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5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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6 | * |
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7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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8 | * Permission to use, copy, modify, and distribute this |
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9 | * software is freely granted, provided that this notice |
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10 | * is preserved. |
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11 | * ==================================================== |
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12 | */ |
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13 | |
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14 | /* __ieee754_remainder(x,p) |
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15 | * Return : |
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16 | * returns x REM p = x - [x/p]*p as if in infinite |
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17 | * precise arithmetic, where [x/p] is the (infinite bit) |
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18 | * integer nearest x/p (in half way case choose the even one). |
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19 | * Method : |
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20 | * Based on fmod() return x-[x/p]chopped*p exactlp. |
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21 | */ |
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22 | |
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23 | #include "fdlibm.h" |
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24 | |
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25 | #ifndef _DOUBLE_IS_32BITS |
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26 | |
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27 | #ifdef __STDC__ |
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28 | static const double zero = 0.0; |
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29 | #else |
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30 | static double zero = 0.0; |
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31 | #endif |
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32 | |
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33 | |
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34 | #ifdef __STDC__ |
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35 | double __ieee754_remainder(double x, double p) |
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36 | #else |
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37 | double __ieee754_remainder(x,p) |
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38 | double x,p; |
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39 | #endif |
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40 | { |
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41 | __int32_t hx,hp; |
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42 | __uint32_t sx,lx,lp; |
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43 | double p_half; |
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44 | |
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45 | EXTRACT_WORDS(hx,lx,x); |
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46 | EXTRACT_WORDS(hp,lp,p); |
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47 | sx = hx&0x80000000; |
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48 | hp &= 0x7fffffff; |
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49 | hx &= 0x7fffffff; |
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50 | |
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51 | /* purge off exception values */ |
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52 | if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */ |
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53 | if((hx>=0x7ff00000)|| /* x not finite */ |
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54 | ((hp>=0x7ff00000)&& /* p is NaN */ |
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55 | (((hp-0x7ff00000)|lp)!=0))) |
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56 | return (x*p)/(x*p); |
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57 | |
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58 | |
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59 | if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */ |
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60 | if (((hx-hp)|(lx-lp))==0) return zero*x; |
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61 | x = fabs(x); |
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62 | p = fabs(p); |
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63 | if (hp<0x00200000) { |
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64 | if(x+x>p) { |
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65 | x-=p; |
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66 | if(x+x>=p) x -= p; |
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67 | } |
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68 | } else { |
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69 | p_half = 0.5*p; |
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70 | if(x>p_half) { |
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71 | x-=p; |
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72 | if(x>=p_half) x -= p; |
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73 | } |
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74 | } |
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75 | GET_HIGH_WORD(hx,x); |
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76 | SET_HIGH_WORD(x,hx^sx); |
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77 | return x; |
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78 | } |
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79 | |
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80 | #endif /* defined(_DOUBLE_IS_32BITS) */ |
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