src/math/__cosdf.c

   1 /* origin: FreeBSD /usr/src/lib/msun/src/k_cosf.c */
   2 /*
   3  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   4  * Debugged and optimized by Bruce D. Evans.
   5  */
   6 /*
   7  * ====================================================
   8  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   9  *
  10  * Developed at SunPro, a Sun Microsystems, Inc. business.
  11  * Permission to use, copy, modify, and distribute this
  12  * software is freely granted, provided that this notice
  13  * is preserved.
  14  * ====================================================
  15  */
  16
  17 #include "libm.h"
  18
  19 /* |cos(x) - c(x)| < 2**-34.1 (~[-5.37e-11, 5.295e-11]). */
  20 static const double
  21 C0  = -0x1ffffffd0c5e81.0p-54, /* -0.499999997251031003120 */
  22 C1  =  0x155553e1053a42.0p-57, /*  0.0416666233237390631894 */
  23 C2  = -0x16c087e80f1e27.0p-62, /* -0.00138867637746099294692 */
  24 C3  =  0x199342e0ee5069.0p-68; /*  0.0000243904487962774090654 */
  25
  26 float __cosdf(double x)
  27 {
  28         double_t r, w, z;
  29
  30         /* Try to optimize for parallel evaluation as in __tandf.c. */
  31         z = x*x;
  32         w = z*z;
  33         r = C2+z*C3;
  34         return ((1.0+z*C0) + w*C1) + (w*z)*r;
  35 }