diff options
Diffstat (limited to 'REORG.TODO/sysdeps/ieee754/dbl-64/s_cbrt.c')
| -rw-r--r-- | REORG.TODO/sysdeps/ieee754/dbl-64/s_cbrt.c | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/ieee754/dbl-64/s_cbrt.c b/REORG.TODO/sysdeps/ieee754/dbl-64/s_cbrt.c new file mode 100644 index 0000000000..689abc89ec --- /dev/null +++ b/REORG.TODO/sysdeps/ieee754/dbl-64/s_cbrt.c @@ -0,0 +1,76 @@ +/* Compute cubic root of double value. + Copyright (C) 1997-2017 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 Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include <math.h> +#include <math_private.h> + + +#define CBRT2 1.2599210498948731648 /* 2^(1/3) */ +#define SQR_CBRT2 1.5874010519681994748 /* 2^(2/3) */ + +static const double factor[5] = +{ + 1.0 / SQR_CBRT2, + 1.0 / CBRT2, + 1.0, + CBRT2, + SQR_CBRT2 +}; + + +double +__cbrt (double x) +{ + double xm, ym, u, t2; + int xe; + + /* Reduce X. XM now is an range 1.0 to 0.5. */ + xm = __frexp (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 = (0.354895765043919860 + + ((1.50819193781584896 + + ((-2.11499494167371287 + + ((2.44693122563534430 + + ((-1.83469277483613086 + + (0.784932344976639262 - 0.145263899385486377 * 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 __ldexp (x > 0.0 ? ym : -ym, xe / 3); +} +weak_alias (__cbrt, cbrt) +#ifdef NO_LONG_DOUBLE +strong_alias (__cbrt, __cbrtl) +weak_alias (__cbrt, cbrtl) +#endif |