74 lines
1.6 KiB
C
74 lines
1.6 KiB
C
/* sf_tanh.c -- float version of s_tanh.c.
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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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*/
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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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#include "fdlibm.h"
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#ifdef __STDC__
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static const volatile float one=1.0, two=2.0, tiny = 1.0e-30;
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#else
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static volatile float one=1.0, two=2.0, tiny = 1.0e-30;
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#endif
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#ifdef __STDC__
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float tanhf(float x)
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#else
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float tanhf(x)
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float x;
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#endif
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{
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float t,z;
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__int32_t jx,ix;
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GET_FLOAT_WORD(jx,x);
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ix = jx&0x7fffffff;
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/* x is INF or NaN */
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if(!FLT_UWORD_IS_FINITE(ix)) {
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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 < 0x41b00000) { /* |x|<22 */
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if (ix<0x24000000) /* |x|<2**-55 */
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return x*(one+x); /* tanh(small) = small */
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if (ix>=0x3f800000) { /* |x|>=1 */
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t = expm1f(two*fabsf(x));
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z = one - two/(t+two);
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} else {
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t = expm1f(-two*fabsf(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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#ifdef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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double tanh(double x)
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#else
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double tanh(x)
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double x;
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#endif
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{
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return (double) tanhf((float) x);
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */
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