1997-04-05 01:26:47 +00:00
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/* Compute cubic root of double value.
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2018-01-01 00:32:25 +00:00
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Copyright (C) 1997-2018 Free Software Foundation, Inc.
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1997-04-05 01:26:47 +00:00
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This file is part of the GNU C Library.
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Contributed by Dirk Alboth <dirka@uni-paderborn.de> and
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Ulrich Drepper <drepper@cygnus.com>, 1997.
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1996-03-05 21:41:30 +00:00
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1997-04-05 01:26:47 +00:00
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The GNU C Library is free software; you can redistribute it and/or
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2001-07-06 04:58:11 +00:00
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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1997-04-05 01:26:47 +00:00
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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2001-07-06 04:58:11 +00:00
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Lesser General Public License for more details.
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1997-04-05 01:26:47 +00:00
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2001-07-06 04:58:11 +00:00
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You should have received a copy of the GNU Lesser General Public
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2012-02-09 23:18:22 +00:00
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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1996-03-05 21:41:30 +00:00
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2012-03-09 19:29:16 +00:00
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#include <math.h>
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#include <math_private.h>
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2017-09-29 23:54:33 +00:00
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#include <libm-alias-double.h>
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1996-03-05 21:41:30 +00:00
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1997-04-05 01:26:47 +00:00
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#define CBRT2 1.2599210498948731648 /* 2^(1/3) */
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#define SQR_CBRT2 1.5874010519681994748 /* 2^(2/3) */
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1997-04-05 01:26:47 +00:00
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static const double factor[5] =
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1996-03-05 21:41:30 +00:00
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{
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1997-04-05 01:26:47 +00:00
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1.0 / SQR_CBRT2,
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1.0 / CBRT2,
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1.0,
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CBRT2,
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SQR_CBRT2
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};
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1996-03-05 21:41:30 +00:00
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1997-04-05 01:26:47 +00:00
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double
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__cbrt (double x)
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{
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double xm, ym, u, t2;
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int xe;
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1996-03-05 21:41:30 +00:00
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1997-04-05 01:26:47 +00:00
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/* Reduce X. XM now is an range 1.0 to 0.5. */
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xm = __frexp (fabs (x), &xe);
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1996-03-05 21:41:30 +00:00
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1997-04-05 01:26:47 +00:00
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/* If X is not finite or is null return it (with raising exceptions
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Update.
1997-10-29 21:20 Ulrich Drepper <drepper@cygnus.com>
* libio/strops.c (_IO_str_seekoff): If mode is zero and the read/write
pointers are tied set mode according to current stream mode.
* include/features.h [_GNU_SOURCE] (_POSIX_C_SOURCE): Define to
199506L.
Define _XOPEN_SOURCE to 500 if _POSIX_C_SOURCE is defined.
* manual/creature.texi: Describe this.
* manual/socket.texi: Describe connect, accept, send, sendmsg, sendto,
recv, recvfrom, and recvmsg as cancelation points.
* sysdeps/unix/inet/syscalls.list: Add __libc_* names for these
functions.
1997-10-17 Andreas Jaeger <aj@arthur.rhein-neckar.de>
* Make-dist (try-sysdeps): Don't look for stub files anymore.
* manual/maint.texi (Porting): Remove another reference to stub
directory.
* sysdeps/unix/bsd/sun/sethostid.c: Include stub version from
generic subdir.
* sysdeps/unix/sysv/irix4/reboot.c: Likewise.
* sysdeps/unix/sysv/irix4/swapon.c: Likewise
1997-10-29 03:54 Ulrich Drepper <drepper@cygnus.com>
* resolv/nss_dns/dns-host.c: Change variable pointed to by h_errnop
in all error cases (PR 244).
1997-10-29 00:56 Ulrich Drepper <drepper@cygnus.com>
* posix/glob.c: Fix handling of expressions like "*/" (PR 325).
Optimize by using mempcpy.
1997-10-17 Andreas Jaeger <aj@arthur.rhein-neckar.de>
* po/Makefile ($(mo-installed)): Don't fail during installation if
files don't exist (might happen if msgfmt doesn't exist) (PR 328).
Suggested by Wolfram Gloger <wmglo@dent.med.uni-muenchen.de>.
1997-10-24 Andreas Jaeger <aj@arthur.rhein-neckar.de>
* sysdeps/generic/bits/errno.h (ENOMSG): Define it.
Pointed out by Klaus Espenlaub
<kespenla@hydra.informatik.uni-ulm.de> (PR libc/259).
1997-10-28 17:40 Ulrich Drepper <drepper@cygnus.com>
* sysdeps/libm-ieee754/s_cbrt.c: Testing the returned exponent for
zero isn't enough to determine illegal arguments.
* sysdeps/libm-ieee754/s_cbrtf.c: Likewise.
* sysdeps/libm-ieee754/s_cbrtl.c: Likewise.
1997-10-28 17:14 Ulrich Drepper <drepper@cygnus.com>
* manual/filesys.texi (S_ISVTX): Describe that it is available with
_BSD_SOURCE only.
Reported by Jochen Hein <jochen.hein@delphi.central.de>.
1997-10-28 04:26 Ulrich Drepper <drepper@cygnus.com>
* time/tzfile.c (__tzfile_compute): Use negated value of offset for
timezone variable.
* time/tzset.c (tz_compute): Likewise.
Reported by Erik Troan <ewt@redhat.com>.
1997-10-28 02:51 Ulrich Drepper <drepper@cygnus.com>
* manual/filesys.texi: Correct prototype in readdir_r description.
Reported by Jim Meyering <meyering@eng.ascend.com>.
1997-10-27 Andreas Jaeger <aj@arthur.rhein-neckar.de>
* math/libm-test.c (cbrt_test): Add test for cbrt(0.970299).
1997-10-26 19:39 Zack Weinberg <zack@rabi.phys.columbia.edu>
* stdlib/l64a.c: Produce a useful result for n < 0.
* stdlib/a64l.c: Use unsigned type for working variable.
* manual/string.texi (general): Grammar, typo, overfull fixes.
(strlen): Insert warning about sizeof(char *).
(a64l, l64a): Make documentation agree with implementation.
* libio/iofdopen.c: Use _IO_FILE_complete, not _IO_FILE_plus.
* posix/unistd.h: Add prototypes for __pread, __pread64, __pwrite
1997-10-29 20:33:40 +00:00
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if necessary.
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Note: *Our* version of `frexp' sets XE to zero if the argument is
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Inf or NaN. This is not portable but faster. */
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if (xe == 0 && fpclassify (x) <= FP_ZERO)
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1997-04-05 01:26:47 +00:00
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return x + x;
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1996-03-05 21:41:30 +00:00
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2013-10-17 14:03:24 +00:00
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u = (0.354895765043919860
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+ ((1.50819193781584896
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+ ((-2.11499494167371287
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+ ((2.44693122563534430
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+ ((-1.83469277483613086
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+ (0.784932344976639262 - 0.145263899385486377 * xm)
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* xm)
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* xm))
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1997-04-05 01:26:47 +00:00
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* xm))
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2013-10-17 14:03:24 +00:00
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* xm))
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* xm));
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1996-03-05 21:41:30 +00:00
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1997-04-05 01:26:47 +00:00
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t2 = u * u * u;
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1996-03-05 21:41:30 +00:00
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1997-04-05 01:26:47 +00:00
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ym = u * (t2 + 2.0 * xm) / (2.0 * t2 + xm) * factor[2 + xe % 3];
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1996-03-05 21:41:30 +00:00
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1997-04-05 01:26:47 +00:00
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return __ldexp (x > 0.0 ? ym : -ym, xe / 3);
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1996-03-05 21:41:30 +00:00
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}
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2017-09-29 23:54:33 +00:00
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libm_alias_double (__cbrt, cbrt)
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