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annotate src/libm/s_cos.c @ 3197:434ce3242e1c

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Alexei Tereschenko Why not to use hardware vertex processing instead of software one if it is available in D3D render driver? With hardware processing testsprite2 runs three times faster on all videocards which I could test.
author Sam Lantinga <slouken@libsdl.org>
date Tue, 16 Jun 2009 14:34:15 +0000
parents dc1eb82ffdaa
children
rev   line source
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a98604b691c8 Expanded the libm support and put it into a separate directory.
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1 /* @(#)s_cos.c 5.1 93/09/24 */
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2 /*
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3 * ====================================================
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4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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5 *
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6 * Developed at SunPro, a Sun Microsystems, Inc. business.
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7 * Permission to use, copy, modify, and distribute this
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8 * software is freely granted, provided that this notice
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9 * is preserved.
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10 * ====================================================
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11 */
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12
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13 #if defined(LIBM_SCCS) && !defined(lint)
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14 static const char rcsid[] =
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15 "$NetBSD: s_cos.c,v 1.7 1995/05/10 20:47:02 jtc Exp $";
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16 #endif
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17
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18 /* cos(x)
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19 * Return cosine function of x.
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20 *
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21 * kernel function:
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22 * __kernel_sin ... sine function on [-pi/4,pi/4]
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23 * __kernel_cos ... cosine function on [-pi/4,pi/4]
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24 * __ieee754_rem_pio2 ... argument reduction routine
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25 *
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26 * Method.
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27 * Let S,C and T denote the sin, cos and tan respectively on
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28 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
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29 * in [-pi/4 , +pi/4], and let n = k mod 4.
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30 * We have
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31 *
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32 * n sin(x) cos(x) tan(x)
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33 * ----------------------------------------------------------
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34 * 0 S C T
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35 * 1 C -S -1/T
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36 * 2 -S -C T
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37 * 3 -C S -1/T
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38 * ----------------------------------------------------------
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39 *
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40 * Special cases:
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41 * Let trig be any of sin, cos, or tan.
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42 * trig(+-INF) is NaN, with signals;
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43 * trig(NaN) is that NaN;
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44 *
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45 * Accuracy:
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46 * TRIG(x) returns trig(x) nearly rounded
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47 */
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48
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49 #include "math.h"
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50 #include "math_private.h"
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51
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52 libm_hidden_proto(cos)
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53 #ifdef __STDC__
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54 double cos(double x)
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55 #else
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56 double cos(x)
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57 double x;
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58 #endif
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59 {
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60 double y[2], z = 0.0;
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61 int32_t n, ix;
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62
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63 /* High word of x. */
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64 GET_HIGH_WORD(ix, x);
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65
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66 /* |x| ~< pi/4 */
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67 ix &= 0x7fffffff;
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68 if (ix <= 0x3fe921fb)
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69 return __kernel_cos(x, z);
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70
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71 /* cos(Inf or NaN) is NaN */
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72 else if (ix >= 0x7ff00000)
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73 return x - x;
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74
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75 /* argument reduction needed */
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76 else {
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77 n = __ieee754_rem_pio2(x, y);
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78 switch (n & 3) {
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79 case 0:
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80 return __kernel_cos(y[0], y[1]);
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81 case 1:
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82 return -__kernel_sin(y[0], y[1], 1);
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83 case 2:
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84 return -__kernel_cos(y[0], y[1]);
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85 default:
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86 return __kernel_sin(y[0], y[1], 1);
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87 }
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88 }
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89 }
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90
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91 libm_hidden_def(cos)