| 1 | /* s_tanhf.c -- float version of s_tanh.c.
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| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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| 3 | */
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| 4 |
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| 5 | /*
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| 6 | * ====================================================
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| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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| 8 | *
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| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business.
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| 10 | * Permission to use, copy, modify, and distribute this
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| 11 | * software is freely granted, provided that this notice
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| 12 | * is preserved.
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| 13 | * ====================================================
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| 14 | */
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| 15 |
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| 16 | #ifndef lint
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| 17 | static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_tanhf.c,v 1.7 2002/05/28 18:15:04 alfred Exp $";
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| 18 | #endif
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| 19 |
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| 20 | #include "math.h"
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| 21 | #include "math_private.h"
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| 22 |
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| 23 | static const float one=1.0, two=2.0, tiny = 1.0e-30;
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| 24 |
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| 25 | float
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| 26 | tanhf(float x)
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| 27 | {
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| 28 | float t,z;
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| 29 | int32_t jx,ix;
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| 30 |
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| 31 | GET_FLOAT_WORD(jx,x);
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| 32 | ix = jx&0x7fffffff;
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| 33 |
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| 34 | /* x is INF or NaN */
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| 35 | if(ix>=0x7f800000) {
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| 36 | if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
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| 37 | else return one/x-one; /* tanh(NaN) = NaN */
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| 38 | }
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| 39 |
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| 40 | /* |x| < 22 */
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| 41 | if (ix < 0x41b00000) { /* |x|<22 */
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| 42 | if (ix<0x24000000) /* |x|<2**-55 */
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| 43 | return x*(one+x); /* tanh(small) = small */
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| 44 | if (ix>=0x3f800000) { /* |x|>=1 */
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| 45 | t = expm1f(two*fabsf(x));
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| 46 | z = one - two/(t+two);
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| 47 | } else {
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| 48 | t = expm1f(-two*fabsf(x));
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| 49 | z= -t/(t+two);
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| 50 | }
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| 51 | /* |x| > 22, return +-1 */
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| 52 | } else {
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| 53 | z = one - tiny; /* raised inexact flag */
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| 54 | }
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| 55 | return (jx>=0)? z: -z;
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| 56 | }
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