GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libm/src/s_tanh.c Lines: 16 18 88.9 %
Date: 2017-11-13 Branches: 9 12 75.0 %

Line Branch Exec Source
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/* @(#)s_tanh.c 5.1 93/09/24 */
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/*
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 * ====================================================
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 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 *
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 * Developed at SunPro, a Sun Microsystems, Inc. business.
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 * Permission to use, copy, modify, and distribute this
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 * software is freely granted, provided that this notice
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 * is preserved.
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 * ====================================================
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 */
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/* Tanh(x)
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 * Return the Hyperbolic Tangent of x
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 *
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 * Method :
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 *				       x    -x
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 *				      e  - e
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 *	0. tanh(x) is defined to be -----------
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 *				       x    -x
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 *				      e  + e
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 *	1. reduce x to non-negative by tanh(-x) = -tanh(x).
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 *	2.  0      <= x <  2**-55 : tanh(x) := x*(one+x)
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 *					        -t
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 *	    2**-55 <= x <  1      : tanh(x) := -----; t = expm1(-2x)
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 *					       t + 2
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 *						     2
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 *	    1      <= x <  22.0   : tanh(x) := 1-  ----- ; t=expm1(2x)
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 *						   t + 2
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 *	    22.0   <= x <= INF    : tanh(x) := 1.
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 *
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 * Special cases:
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 *	tanh(NaN) is NaN;
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 *	only tanh(0)=0 is exact for finite argument.
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 */
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#include <float.h>
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#include <math.h>
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#include "math_private.h"
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static const double one=1.0, two=2.0, tiny = 1.0e-300;
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double
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tanh(double x)
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{
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	double t,z;
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	int32_t jx,ix,lx;
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    /* High word of |x|. */
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	EXTRACT_WORDS(jx,lx,x);
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	ix = jx&0x7fffffff;
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    /* x is INF or NaN */
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	if(ix>=0x7ff00000) {
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	    if (jx>=0) return one/x+one;    /* tanh(+-inf)=+-1 */
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	    else       return one/x-one;    /* tanh(NaN) = NaN */
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	}
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    /* |x| < 22 */
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	if (ix < 0x40360000) {		/* |x|<22 */
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	    if ((ix | lx) == 0)
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		return x;		/* x == +-0 */
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	    if (ix<0x3c800000) 		/* |x|<2**-55 */
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		return x*(one+x);    	/* tanh(small) = small */
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	    if (ix>=0x3ff00000) {	/* |x|>=1  */
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		t = expm1(two*fabs(x));
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		z = one - two/(t+two);
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	    } else {
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	        t = expm1(-two*fabs(x));
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	        z= -t/(t+two);
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	    }
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    /* |x| >= 22, return +-1 */
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	} else {
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	    z = one - tiny;		/* raised inexact flag */
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	}
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	return (jx>=0)? z: -z;
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}
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DEF_STD(tanh);
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LDBL_MAYBE_UNUSED_CLONE(tanh);