1 | |
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2 | /* @(#)z_sinef.c 1.0 98/08/13 */ |
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3 | /****************************************************************** |
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4 | * The following routines are coded directly from the algorithms |
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5 | * and coefficients given in "Software Manual for the Elementary |
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6 | * Functions" by William J. Cody, Jr. and William Waite, Prentice |
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7 | * Hall, 1980. |
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8 | ******************************************************************/ |
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9 | /****************************************************************** |
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10 | * sine generator |
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11 | * |
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12 | * Input: |
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13 | * x - floating point value |
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14 | * cosine - indicates cosine value |
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15 | * |
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16 | * Output: |
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17 | * Sine of x. |
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18 | * |
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19 | * Description: |
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20 | * This routine calculates sines and cosines. |
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21 | * |
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22 | *****************************************************************/ |
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23 | |
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24 | #include "fdlibm.h" |
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25 | #include "zmath.h" |
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26 | |
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27 | static const float HALF_PI = 1.570796326; |
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28 | static const float ONE_OVER_PI = 0.318309886; |
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29 | static const float r[] = { -0.1666665668, |
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30 | 0.8333025139e-02, |
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31 | -0.1980741872e-03, |
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32 | 0.2601903036e-5 }; |
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33 | |
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34 | float |
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35 | sinef (float x, |
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36 | int cosine) |
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37 | { |
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38 | int sgn, N; |
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39 | float y, XN, g, R, res; |
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40 | float YMAX = 210828714.0; |
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41 | |
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42 | switch (numtestf (x)) |
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43 | { |
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44 | case NAN: |
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45 | errno = EDOM; |
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46 | return (x); |
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47 | case INF: |
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48 | errno = EDOM; |
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49 | return (z_notanum_f.f); |
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50 | } |
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51 | |
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52 | /* Use sin and cos properties to ease computations. */ |
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53 | if (cosine) |
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54 | { |
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55 | sgn = 1; |
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56 | y = fabsf (x) + HALF_PI; |
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57 | } |
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58 | else |
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59 | { |
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60 | if (x < 0.0) |
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61 | { |
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62 | sgn = -1; |
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63 | y = -x; |
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64 | } |
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65 | else |
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66 | { |
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67 | sgn = 1; |
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68 | y = x; |
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69 | } |
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70 | } |
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71 | |
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72 | /* Check for values of y that will overflow here. */ |
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73 | if (y > YMAX) |
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74 | { |
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75 | errno = ERANGE; |
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76 | return (x); |
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77 | } |
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78 | |
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79 | /* Calculate the exponent. */ |
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80 | if (y < 0.0) |
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81 | N = (int) (y * ONE_OVER_PI - 0.5); |
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82 | else |
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83 | N = (int) (y * ONE_OVER_PI + 0.5); |
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84 | XN = (float) N; |
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85 | |
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86 | if (N & 1) |
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87 | sgn = -sgn; |
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88 | |
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89 | if (cosine) |
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90 | XN -= 0.5; |
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91 | |
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92 | y = fabsf (x) - XN * __PI; |
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93 | |
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94 | if (-z_rooteps_f < y && y < z_rooteps_f) |
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95 | res = y; |
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96 | |
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97 | else |
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98 | { |
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99 | g = y * y; |
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100 | |
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101 | /* Calculate the Taylor series. */ |
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102 | R = (((r[3] * g + r[2]) * g + r[1]) * g + r[0]) * g; |
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103 | |
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104 | /* Finally, compute the result. */ |
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105 | res = y + y * R; |
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106 | } |
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107 | |
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108 | res *= sgn; |
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109 | |
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110 | return (res); |
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111 | } |
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