2000-02-18 03:39:52 +08:00
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/* ef_acosh.c -- float version of e_acosh.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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*/
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#include "fdlibm.h"
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#ifdef __STDC__
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static const float
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#else
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static float
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#endif
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one = 1.0,
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ln2 = 6.9314718246e-01; /* 0x3f317218 */
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#ifdef __STDC__
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float __ieee754_acoshf(float x)
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#else
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float __ieee754_acoshf(x)
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float x;
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#endif
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{
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float t;
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__int32_t hx;
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GET_FLOAT_WORD(hx,x);
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if(hx<0x3f800000) { /* x < 1 */
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return (x-x)/(x-x);
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} else if(hx >=0x4d800000) { /* x > 2**28 */
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2001-04-04 21:33:01 +08:00
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if(!FLT_UWORD_IS_FINITE(hx)) { /* x is inf of NaN */
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2000-02-18 03:39:52 +08:00
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return x+x;
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} else
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return __ieee754_logf(x)+ln2; /* acosh(huge)=log(2x) */
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} else if (hx==0x3f800000) {
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return 0.0; /* acosh(1) = 0 */
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} else if (hx > 0x40000000) { /* 2**28 > x > 2 */
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t=x*x;
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return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one)));
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} else { /* 1<x<2 */
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t = x-one;
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return log1pf(t+__ieee754_sqrtf((float)2.0*t+t*t));
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}
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}
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