From abfbdde177c3a7155070dda1b2cdc8292054cc26 Mon Sep 17 00:00:00 2001 From: Ulrich Drepper Date: Wed, 14 Jul 1999 00:54:57 +0000 Subject: Update. --- sysdeps/ieee754/flt-32/s_cbrtf.c | 64 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) create mode 100644 sysdeps/ieee754/flt-32/s_cbrtf.c (limited to 'sysdeps/ieee754/flt-32/s_cbrtf.c') diff --git a/sysdeps/ieee754/flt-32/s_cbrtf.c b/sysdeps/ieee754/flt-32/s_cbrtf.c new file mode 100644 index 0000000000..fa0fef9987 --- /dev/null +++ b/sysdeps/ieee754/flt-32/s_cbrtf.c @@ -0,0 +1,64 @@ +/* Compute cubic root of float value. + Copyright (C) 1997 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Dirk Alboth and + Ulrich Drepper , 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) */ + +static const double factor[5] = +{ + 1.0 / SQR_CBRT2, + 1.0 / CBRT2, + 1.0, + CBRT2, + SQR_CBRT2 +}; + + +float +__cbrtf (float x) +{ + float xm, ym, u, t2; + int xe; + + /* Reduce X. XM now is an range 1.0 to 0.5. */ + xm = __frexpf (fabsf (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 = (0.492659620528969547 + (0.697570460207922770 + - 0.191502161678719066 * xm) * xm); + + t2 = u * u * u; + + ym = u * (t2 + 2.0 * xm) / (2.0 * t2 + xm) * factor[2 + xe % 3]; + + return __ldexpf (x > 0.0 ? ym : -ym, xe / 3); +} +weak_alias (__cbrtf, cbrtf) -- cgit 1.4.1