| 1 | /* e_acoshf.c -- float version of e_acosh.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/e_acoshf.c,v 1.7 2002/05/28 17:03:12 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
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| 24 | one = 1.0,
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| 25 | ln2 = 6.9314718246e-01; /* 0x3f317218 */
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| 26 |
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| 27 | float
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| 28 | __ieee754_acoshf(float x)
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| 29 | {
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| 30 | float t;
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| 31 | int32_t hx;
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| 32 | GET_FLOAT_WORD(hx,x);
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| 33 | if(hx<0x3f800000) { /* x < 1 */
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| 34 | return (x-x)/(x-x);
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| 35 | } else if(hx >=0x4d800000) { /* x > 2**28 */
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| 36 | if(hx >=0x7f800000) { /* x is inf of NaN */
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| 37 | return x+x;
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| 38 | } else
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| 39 | return __ieee754_logf(x)+ln2; /* acosh(huge)=log(2x) */
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| 40 | } else if (hx==0x3f800000) {
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| 41 | return 0.0; /* acosh(1) = 0 */
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| 42 | } else if (hx > 0x40000000) { /* 2**28 > x > 2 */
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| 43 | t=x*x;
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| 44 | return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one)));
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| 45 | } else { /* 1<x<2 */
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| 46 | t = x-one;
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| 47 | return log1pf(t+__ieee754_sqrtf((float)2.0*t+t*t));
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| 48 | }
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| 49 | }
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