//===========================================================================
|
//===========================================================================
|
//
|
//
|
// s_tanh.c
|
// s_tanh.c
|
//
|
//
|
// Part of the standard mathematical function library
|
// Part of the standard mathematical function library
|
//
|
//
|
//===========================================================================
|
//===========================================================================
|
//####ECOSGPLCOPYRIGHTBEGIN####
|
//####ECOSGPLCOPYRIGHTBEGIN####
|
// -------------------------------------------
|
// -------------------------------------------
|
// This file is part of eCos, the Embedded Configurable Operating System.
|
// This file is part of eCos, the Embedded Configurable Operating System.
|
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
|
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
|
//
|
//
|
// eCos is free software; you can redistribute it and/or modify it under
|
// eCos is free software; you can redistribute it and/or modify it under
|
// the terms of the GNU General Public License as published by the Free
|
// the terms of the GNU General Public License as published by the Free
|
// Software Foundation; either version 2 or (at your option) any later version.
|
// Software Foundation; either version 2 or (at your option) any later version.
|
//
|
//
|
// eCos is distributed in the hope that it will be useful, but WITHOUT ANY
|
// eCos is distributed in the hope that it will be useful, but WITHOUT ANY
|
// WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
// WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
// for more details.
|
// for more details.
|
//
|
//
|
// You should have received a copy of the GNU General Public License along
|
// You should have received a copy of the GNU General Public License along
|
// with eCos; if not, write to the Free Software Foundation, Inc.,
|
// with eCos; if not, write to the Free Software Foundation, Inc.,
|
// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
|
// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
|
//
|
//
|
// As a special exception, if other files instantiate templates or use macros
|
// As a special exception, if other files instantiate templates or use macros
|
// or inline functions from this file, or you compile this file and link it
|
// or inline functions from this file, or you compile this file and link it
|
// with other works to produce a work based on this file, this file does not
|
// with other works to produce a work based on this file, this file does not
|
// by itself cause the resulting work to be covered by the GNU General Public
|
// by itself cause the resulting work to be covered by the GNU General Public
|
// License. However the source code for this file must still be made available
|
// License. However the source code for this file must still be made available
|
// in accordance with section (3) of the GNU General Public License.
|
// in accordance with section (3) of the GNU General Public License.
|
//
|
//
|
// This exception does not invalidate any other reasons why a work based on
|
// This exception does not invalidate any other reasons why a work based on
|
// this file might be covered by the GNU General Public License.
|
// this file might be covered by the GNU General Public License.
|
//
|
//
|
// Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
|
// Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
|
// at http://sources.redhat.com/ecos/ecos-license/
|
// at http://sources.redhat.com/ecos/ecos-license/
|
// -------------------------------------------
|
// -------------------------------------------
|
//####ECOSGPLCOPYRIGHTEND####
|
//####ECOSGPLCOPYRIGHTEND####
|
//===========================================================================
|
//===========================================================================
|
//#####DESCRIPTIONBEGIN####
|
//#####DESCRIPTIONBEGIN####
|
//
|
//
|
// Author(s): jlarmour
|
// Author(s): jlarmour
|
// Contributors: jlarmour
|
// Contributors: jlarmour
|
// Date: 1998-02-13
|
// Date: 1998-02-13
|
// Purpose:
|
// Purpose:
|
// Description:
|
// Description:
|
// Usage:
|
// Usage:
|
//
|
//
|
//####DESCRIPTIONEND####
|
//####DESCRIPTIONEND####
|
//
|
//
|
//===========================================================================
|
//===========================================================================
|
|
|
// CONFIGURATION
|
// CONFIGURATION
|
|
|
#include <pkgconf/libm.h> // Configuration header
|
#include <pkgconf/libm.h> // Configuration header
|
|
|
// Include the Math library?
|
// Include the Math library?
|
#ifdef CYGPKG_LIBM
|
#ifdef CYGPKG_LIBM
|
|
|
// Derived from code with the following copyright
|
// Derived from code with the following copyright
|
|
|
|
|
/* @(#)s_tanh.c 1.3 95/01/18 */
|
/* @(#)s_tanh.c 1.3 95/01/18 */
|
/*
|
/*
|
* ====================================================
|
* ====================================================
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
*
|
*
|
* Developed at SunSoft, a Sun Microsystems, Inc. business.
|
* Developed at SunSoft, a Sun Microsystems, Inc. business.
|
* Permission to use, copy, modify, and distribute this
|
* Permission to use, copy, modify, and distribute this
|
* software is freely granted, provided that this notice
|
* software is freely granted, provided that this notice
|
* is preserved.
|
* is preserved.
|
* ====================================================
|
* ====================================================
|
*/
|
*/
|
|
|
/* Tanh(x)
|
/* Tanh(x)
|
* Return the Hyperbolic Tangent of x
|
* Return the Hyperbolic Tangent of x
|
*
|
*
|
* Method :
|
* Method :
|
* x -x
|
* x -x
|
* e - e
|
* e - e
|
* 0. tanh(x) is defined to be -----------
|
* 0. tanh(x) is defined to be -----------
|
* x -x
|
* x -x
|
* e + e
|
* e + e
|
* 1. reduce x to non-negative by tanh(-x) = -tanh(x).
|
* 1. reduce x to non-negative by tanh(-x) = -tanh(x).
|
* 2. 0 <= x <= 2**-55 : tanh(x) := x*(one+x)
|
* 2. 0 <= x <= 2**-55 : tanh(x) := x*(one+x)
|
* -t
|
* -t
|
* 2**-55 < x <= 1 : tanh(x) := -----; t = expm1(-2x)
|
* 2**-55 < x <= 1 : tanh(x) := -----; t = expm1(-2x)
|
* t + 2
|
* t + 2
|
* 2
|
* 2
|
* 1 <= x <= 22.0 : tanh(x) := 1- ----- ; t=expm1(2x)
|
* 1 <= x <= 22.0 : tanh(x) := 1- ----- ; t=expm1(2x)
|
* t + 2
|
* t + 2
|
* 22.0 < x <= INF : tanh(x) := 1.
|
* 22.0 < x <= INF : tanh(x) := 1.
|
*
|
*
|
* Special cases:
|
* Special cases:
|
* tanh(NaN) is NaN;
|
* tanh(NaN) is NaN;
|
* only tanh(0)=0 is exact for finite argument.
|
* only tanh(0)=0 is exact for finite argument.
|
*/
|
*/
|
|
|
#include "mathincl/fdlibm.h"
|
#include "mathincl/fdlibm.h"
|
|
|
static const double one=1.0, two=2.0, tiny = 1.0e-300;
|
static const double one=1.0, two=2.0, tiny = 1.0e-300;
|
|
|
double tanh(double x)
|
double tanh(double x)
|
{
|
{
|
double t,z;
|
double t,z;
|
int jx,ix;
|
int jx,ix;
|
|
|
/* High word of |x|. */
|
/* High word of |x|. */
|
jx = CYG_LIBM_HI(x);
|
jx = CYG_LIBM_HI(x);
|
ix = jx&0x7fffffff;
|
ix = jx&0x7fffffff;
|
|
|
/* x is INF or NaN */
|
/* x is INF or NaN */
|
if(ix>=0x7ff00000) {
|
if(ix>=0x7ff00000) {
|
if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
|
if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
|
else return one/x-one; /* tanh(NaN) = NaN */
|
else return one/x-one; /* tanh(NaN) = NaN */
|
}
|
}
|
|
|
/* |x| < 22 */
|
/* |x| < 22 */
|
if (ix < 0x40360000) { /* |x|<22 */
|
if (ix < 0x40360000) { /* |x|<22 */
|
if (ix<0x3c800000) /* |x|<2**-55 */
|
if (ix<0x3c800000) /* |x|<2**-55 */
|
return x*(one+x); /* tanh(small) = small */
|
return x*(one+x); /* tanh(small) = small */
|
if (ix>=0x3ff00000) { /* |x|>=1 */
|
if (ix>=0x3ff00000) { /* |x|>=1 */
|
t = expm1(two*fabs(x));
|
t = expm1(two*fabs(x));
|
z = one - two/(t+two);
|
z = one - two/(t+two);
|
} else {
|
} else {
|
t = expm1(-two*fabs(x));
|
t = expm1(-two*fabs(x));
|
z= -t/(t+two);
|
z= -t/(t+two);
|
}
|
}
|
/* |x| > 22, return +-1 */
|
/* |x| > 22, return +-1 */
|
} else {
|
} else {
|
z = one - tiny; /* raised inexact flag */
|
z = one - tiny; /* raised inexact flag */
|
}
|
}
|
return (jx>=0)? z: -z;
|
return (jx>=0)? z: -z;
|
}
|
}
|
|
|
#endif // ifdef CYGPKG_LIBM
|
#endif // ifdef CYGPKG_LIBM
|
|
|
// EOF s_tanh.c
|
// EOF s_tanh.c
|
|
|