diff options
Diffstat (limited to 'sysdeps/ieee754/ldbl-96/s_cbrtl.c')
-rw-r--r-- | sysdeps/ieee754/ldbl-96/s_cbrtl.c | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-96/s_cbrtl.c b/sysdeps/ieee754/ldbl-96/s_cbrtl.c new file mode 100644 index 0000000..1d021b7 --- /dev/null +++ b/sysdeps/ieee754/ldbl-96/s_cbrtl.c @@ -0,0 +1,78 @@ +/* Compute cubic root of double value. + Copyright (C) 1997 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Dirk Alboth <dirka@uni-paderborn.de> and + Ulrich Drepper <drepper@cygnus.com>, 1997. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General Public License as + published by the Free Software Foundation; either version 2 of the + License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#include "math.h" +#include "math_private.h" + + +#define CBRT2 1.2599210498948731648 /* 2^(1/3) */ +#define SQR_CBRT2 1.5874010519681994748 /* 2^(2/3) */ + +/* We don't use long double values here since U need not be computed + with full precision. */ +static const double factor[5] = +{ + 1.0 / SQR_CBRT2, + 1.0 / CBRT2, + 1.0, + CBRT2, + SQR_CBRT2 +}; + + +long double +__cbrtl (long double x) +{ + long double xm, ym, u, t2; + int xe; + + /* Reduce X. XM now is an range 1.0 to 0.5. */ + xm = __frexpl (fabs (x), &xe); + + /* If X is not finite or is null return it (with raising exceptions + if necessary. + Note: *Our* version of `frexp' sets XE to zero if the argument is + Inf or NaN. This is not portable but faster. */ + if (xe == 0 && fpclassify (x) <= FP_ZERO) + return x + x; + + u = (0.338058687610520237 + + (1.67595307700780102 + + (-2.82414939754975962 + + (4.09559907378707839 + + (-4.11151425200350531 + + (2.65298938441952296 + + (-0.988553671195413709 + + 0.161617097923756032 * xm) + * xm) + * xm) + * xm) + * xm) + * xm) + *xm); + + t2 = u * u * u; + + ym = u * (t2 + 2.0 * xm) / (2.0 * t2 + xm) * factor[2 + xe % 3]; + + return __ldexpl (x > 0.0 ? ym : -ym, xe / 3); +} +weak_alias (__cbrtl, cbrtl) |