64 lines
1.5 KiB
C
64 lines
1.5 KiB
C
|
/* s_tanhf.c -- float version of s_tanh.c.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/*
|
||
|
|
* ====================================================
|
||
|
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
||
|
|
*
|
||
|
|
* Developed at SunPro, a Sun Microsystems, Inc. business.
|
||
|
|
* Permission to use, copy, modify, and distribute this
|
||
|
|
* software is freely granted, provided that this notice
|
||
|
|
* is preserved.
|
||
|
|
* ====================================================
|
||
|
|
*/
|
||
|
|
|
||
|
|
#if defined(LIBM_SCCS) && !defined(lint)
|
||
|
|
static char rcsid[] = "$NetBSD: s_tanhf.c,v 1.4 1995/05/10 20:48:24 jtc Exp $";
|
||
|
|
#endif
|
||
|
|
|
||
|
|
#include <float.h>
|
||
|
|
#include <math.h>
|
||
|
|
#include <math_private.h>
|
||
|
|
#include <math-underflow.h>
|
||
|
|
#include <libm-alias-float.h>
|
||
|
|
|
||
|
|
static const float one=1.0, two=2.0, tiny = 1.0e-30;
|
||
|
|
|
||
|
|
float __tanhf(float x)
|
||
|
|
{
|
||
|
|
float t,z;
|
||
|
|
int32_t jx,ix;
|
||
|
|
|
||
|
|
GET_FLOAT_WORD(jx,x);
|
||
|
|
ix = jx&0x7fffffff;
|
||
|
|
|
||
|
|
/* x is INF or NaN */
|
||
|
|
if(ix>=0x7f800000) {
|
||
|
|
if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
|
||
|
|
else return one/x-one; /* tanh(NaN) = NaN */
|
||
|
|
}
|
||
|
|
|
||
|
|
/* |x| < 22 */
|
||
|
|
if (ix < 0x41b00000) { /* |x|<22 */
|
||
|
|
if (ix == 0)
|
||
|
|
return x; /* x == +-0 */
|
||
|
|
if (ix<0x24000000) /* |x|<2**-55 */
|
||
|
|
{
|
||
|
|
math_check_force_underflow (x);
|
||
|
|
return x*(one+x); /* tanh(small) = small */
|
||
|
|
}
|
||
|
|
if (ix>=0x3f800000) { /* |x|>=1 */
|
||
|
|
t = __expm1f(two*fabsf(x));
|
||
|
|
z = one - two/(t+two);
|
||
|
|
} else {
|
||
|
|
t = __expm1f(-two*fabsf(x));
|
||
|
|
z= -t/(t+two);
|
||
|
|
}
|
||
|
|
/* |x| > 22, return +-1 */
|
||
|
|
} else {
|
||
|
|
z = one - tiny; /* raised inexact flag */
|
||
|
|
}
|
||
|
|
return (jx>=0)? z: -z;
|
||
|
|
}
|
||
|
|
libm_alias_float (__tanh, tanh)
|