cobalt / cobalt / 286dd7840608e9cf78bc4a603ff2ec2ee39750c5 / . / src / third_party / musl / src / math / __tandf.c

/* origin: FreeBSD /usr/src/lib/msun/src/k_tanf.c */ | |

/* | |

* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. | |

* Optimized by Bruce D. Evans. | |

*/ | |

/* | |

* ==================================================== | |

* Copyright 2004 Sun Microsystems, Inc. All Rights Reserved. | |

* | |

* Permission to use, copy, modify, and distribute this | |

* software is freely granted, provided that this notice | |

* is preserved. | |

* ==================================================== | |

*/ | |

#include "libm.h" | |

/* |tan(x)/x - t(x)| < 2**-25.5 (~[-2e-08, 2e-08]). */ | |

static const double T[] = { | |

0x15554d3418c99f.0p-54, /* 0.333331395030791399758 */ | |

0x1112fd38999f72.0p-55, /* 0.133392002712976742718 */ | |

0x1b54c91d865afe.0p-57, /* 0.0533812378445670393523 */ | |

0x191df3908c33ce.0p-58, /* 0.0245283181166547278873 */ | |

0x185dadfcecf44e.0p-61, /* 0.00297435743359967304927 */ | |

0x1362b9bf971bcd.0p-59, /* 0.00946564784943673166728 */ | |

}; | |

float __tandf(double x, int odd) | |

{ | |

double_t z,r,w,s,t,u; | |

z = x*x; | |

/* | |

* Split up the polynomial into small independent terms to give | |

* opportunities for parallel evaluation. The chosen splitting is | |

* micro-optimized for Athlons (XP, X64). It costs 2 multiplications | |

* relative to Horner's method on sequential machines. | |

* | |

* We add the small terms from lowest degree up for efficiency on | |

* non-sequential machines (the lowest degree terms tend to be ready | |

* earlier). Apart from this, we don't care about order of | |

* operations, and don't need to to care since we have precision to | |

* spare. However, the chosen splitting is good for accuracy too, | |

* and would give results as accurate as Horner's method if the | |

* small terms were added from highest degree down. | |

*/ | |

r = T[4] + z*T[5]; | |

t = T[2] + z*T[3]; | |

w = z*z; | |

s = z*x; | |

u = T[0] + z*T[1]; | |

r = (x + s*u) + (s*w)*(t + w*r); | |

return odd ? -1.0/r : r; | |

} |