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62 lines
1.7 KiB
C
62 lines
1.7 KiB
C
/* e_acoshl.c -- long double version of e_acosh.c.
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* Conversion to long double by Ulrich Drepper,
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* Cygnus Support, drepper@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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/* __ieee754_acoshl(x)
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* Method :
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* Based on
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* acoshl(x) = logl [ x + sqrtl(x*x-1) ]
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* we have
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* acoshl(x) := logl(x)+ln2, if x is large; else
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* acoshl(x) := logl(2x-1/(sqrtl(x*x-1)+x)) if x>2; else
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* acoshl(x) := log1pl(t+sqrtl(2.0*t+t*t)); where t=x-1.
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*
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* Special cases:
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* acoshl(x) is NaN with signal if x<1.
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* acoshl(NaN) is NaN without signal.
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*/
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#include <math.h>
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#include <math_private.h>
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static const long double
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one = 1.0,
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ln2 = 6.931471805599453094287e-01L; /* 0x3FFE, 0xB17217F7, 0xD1CF79AC */
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long double
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__ieee754_acoshl(long double x)
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{
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long double t;
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u_int32_t se,i0,i1;
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GET_LDOUBLE_WORDS(se,i0,i1,x);
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if(se<0x3fff || se & 0x8000) { /* x < 1 */
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return (x-x)/(x-x);
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} else if(se >=0x401d) { /* x > 2**30 */
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if(se >=0x7fff) { /* x is inf of NaN */
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return x+x;
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} else
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return __ieee754_logl(x)+ln2; /* acoshl(huge)=logl(2x) */
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} else if(((se-0x3fff)|i0|i1)==0) {
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return 0.0; /* acosh(1) = 0 */
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} else if (se > 0x4000) { /* 2**28 > x > 2 */
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t=x*x;
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return __ieee754_logl(2.0*x-one/(x+__ieee754_sqrtl(t-one)));
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} else { /* 1<x<2 */
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t = x-one;
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return __log1pl(t+__ieee754_sqrtl(2.0*t+t*t));
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}
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}
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strong_alias (__ieee754_acoshl, __acoshl_finite)
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