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The Cephes Mathematical Library author Steve Moshier has released the Cephes Mathematical Library under the BSD license. This patch patch replaces the cephes license with the BSD license for all Cephes Mathematical Library code. See also: https://bugs.gentoo.org/687276 See also: https://lists.debian.org/debian-legal/2004/12/msg00295.html See also: https://github.com/deepmind/torch-cephes/blob/master/LICENSE.txt See also: https://github.com/nearform/node-cephes/blob/master/LICENSE # Conflicts: # src/math/readme.txt
165 lines
3.9 KiB
C
165 lines
3.9 KiB
C
/* tanh.c
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*
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* Hyperbolic tangent
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*
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*
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*
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* SYNOPSIS:
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*
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* double x, y, tanh();
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*
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* y = tanh( x );
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*
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*
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*
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* DESCRIPTION:
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*
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* Returns hyperbolic tangent of argument in the range MINLOG to
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* MAXLOG.
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*
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* A rational function is used for |x| < 0.625. The form
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* x + x**3 P(x)/Q(x) of Cody _& Waite is employed.
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* Otherwise,
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* tanh(x) = sinh(x)/cosh(x) = 1 - 2/(exp(2x) + 1).
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*
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*
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*
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* ACCURACY:
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*
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* Relative error:
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* arithmetic domain # trials peak rms
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* DEC -2,2 50000 3.3e-17 6.4e-18
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* IEEE -2,2 30000 2.5e-16 5.8e-17
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*
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*/
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/*
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Cephes Math Library Release 2.8: June, 2000
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Copyright 1984, 1995, 2000 by Stephen L. Moshier
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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3. Neither the name of the <ORGANIZATION> nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "mconf.h"
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#ifdef UNK
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static double P[] = {
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-9.64399179425052238628E-1,
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-9.92877231001918586564E1,
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-1.61468768441708447952E3
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};
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static double Q[] = {
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/* 1.00000000000000000000E0,*/
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1.12811678491632931402E2,
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2.23548839060100448583E3,
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4.84406305325125486048E3
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};
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#endif
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#ifdef DEC
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static unsigned short P[] = {
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0140166,0161335,0053753,0075126,
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0141706,0111520,0070463,0040552,
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0142711,0153001,0101300,0025430
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};
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static unsigned short Q[] = {
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/*0040200,0000000,0000000,0000000,*/
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0041741,0117624,0051300,0156060,
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0043013,0133720,0071251,0127717,
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0043227,0060201,0021020,0020136
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};
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#endif
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#ifdef IBMPC
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static unsigned short P[] = {
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0x6f4b,0xaafd,0xdc5b,0xbfee,
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0x682d,0x0e26,0xd26a,0xc058,
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0x0563,0x3058,0x3ac0,0xc099
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};
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static unsigned short Q[] = {
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/*0x0000,0x0000,0x0000,0x3ff0,*/
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0x1b86,0x8a58,0x33f2,0x405c,
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0x35fa,0x0e55,0x76fa,0x40a1,
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0x040c,0x2442,0xec10,0x40b2
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};
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#endif
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#ifdef MIEEE
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static unsigned short P[] = {
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0xbfee,0xdc5b,0xaafd,0x6f4b,
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0xc058,0xd26a,0x0e26,0x682d,
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0xc099,0x3ac0,0x3058,0x0563
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};
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static unsigned short Q[] = {
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0x405c,0x33f2,0x8a58,0x1b86,
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0x40a1,0x76fa,0x0e55,0x35fa,
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0x40b2,0xec10,0x2442,0x040c
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};
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#endif
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#ifdef ANSIPROT
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extern double fabs ( double );
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extern double c_exp ( double );
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extern double polevl ( double, void *, int );
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extern double p1evl ( double, void *, int );
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#else
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double fabs(), c_exp(), polevl(), p1evl();
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#endif
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extern double MAXLOG;
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double c_tanh(x)
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double x;
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{
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double s, z;
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#ifdef MINUSZERO
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if( x == 0.0 )
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return(x);
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#endif
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z = fabs(x);
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if( z > 0.5 * MAXLOG )
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{
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if( x > 0 )
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return( 1.0 );
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else
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return( -1.0 );
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}
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if( z >= 0.625 )
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{
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s = c_exp(2.0*z);
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z = 1.0 - 2.0/(s + 1.0);
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if( x < 0 )
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z = -z;
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}
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else
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{
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if( x == 0.0 )
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return(x);
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s = x * x;
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z = polevl( s, P, 2 )/p1evl(s, Q, 3);
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z = x * s * z;
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z = x + z;
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}
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return( z );
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}
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