112 lines
2.2 KiB
C
112 lines
2.2 KiB
C
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/* @(#)z_sinef.c 1.0 98/08/13 */
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/******************************************************************
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* The following routines are coded directly from the algorithms
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* and coefficients given in "Software Manual for the Elementary
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* Functions" by William J. Cody, Jr. and William Waite, Prentice
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* Hall, 1980.
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******************************************************************/
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/******************************************************************
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* sine generator
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*
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* Input:
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* x - floating point value
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* cosine - indicates cosine value
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*
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* Output:
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* Sine of x.
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*
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* Description:
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* This routine calculates sines and cosines.
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*
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*****************************************************************/
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#include "fdlibm.h"
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#include "zmath.h"
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static const float HALF_PI = 1.570796326;
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static const float ONE_OVER_PI = 0.318309886;
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static const float r[] = { -0.1666665668,
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0.8333025139e-02,
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-0.1980741872e-03,
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0.2601903036e-5 };
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float
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sinef (float x,
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int cosine)
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{
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int sgn, N;
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float y, XN, g, R, res;
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float YMAX = 210828714.0;
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switch (numtestf (x))
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{
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case NAN:
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errno = EDOM;
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return (x);
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case INF:
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errno = EDOM;
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return (z_notanum_f.f);
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}
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/* Use sin and cos properties to ease computations. */
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if (cosine)
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{
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sgn = 1;
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y = fabsf (x) + HALF_PI;
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}
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else
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{
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if (x < 0.0)
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{
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sgn = -1;
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y = -x;
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}
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else
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{
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sgn = 1;
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y = x;
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}
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}
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/* Check for values of y that will overflow here. */
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if (y > YMAX)
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{
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errno = ERANGE;
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return (x);
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}
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/* Calculate the exponent. */
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if (y < 0.0)
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N = (int) (y * ONE_OVER_PI - 0.5);
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else
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N = (int) (y * ONE_OVER_PI + 0.5);
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XN = (float) N;
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if (N & 1)
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sgn = -sgn;
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if (cosine)
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XN -= 0.5;
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y = fabsf (x) - XN * __PI;
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if (-z_rooteps_f < y && y < z_rooteps_f)
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res = y;
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else
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{
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g = y * y;
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/* Calculate the Taylor series. */
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R = (((r[3] * g + r[2]) * g + r[1]) * g + r[0]) * g;
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/* Finally, compute the result. */
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res = y + y * R;
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}
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res *= sgn;
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return (res);
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}
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