OpenCores
URL https://opencores.org/ocsvn/or1k/or1k/trunk

Subversion Repositories or1k

[/] [or1k/] [trunk/] [linux/] [uClibc/] [libm/] [e_cosh.c] - Blame information for rev 1776

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 1325 phoenix 
/* @(#)e_cosh.c 5.1 93/09/24 */
2 
/*
3 
 * ====================================================
4 
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 
 *
6 
 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 
 * Permission to use, copy, modify, and distribute this
8 
 * software is freely granted, provided that this notice
9 
 * is preserved.
10 
 * ====================================================
11 
 */
12 
 
13 
#if defined(LIBM_SCCS) && !defined(lint)
14 
static char rcsid[] = "$NetBSD: e_cosh.c,v 1.7 1995/05/10 20:44:58 jtc Exp $";
15 
#endif
16 
 
17 
/* __ieee754_cosh(x)
18 
 * Method :
19 
 * mathematically cosh(x) if defined to be (exp(x)+exp(-x))/2
20 
 *      1. Replace x by |x| (cosh(x) = cosh(-x)).
21 
 *      2.
22 
 *                                                      [ exp(x) - 1 ]^2
23 
 *          0        <= x <= ln2/2  :  cosh(x) := 1 + -------------------
24 
 *                                                         2*exp(x)
25 
 *
26 
 *                                                exp(x) +  1/exp(x)
27 
 *          ln2/2    <= x <= 22     :  cosh(x) := -------------------
28 
 *                                                        2
29 
 *          22       <= x <= lnovft :  cosh(x) := exp(x)/2
30 
 *          lnovft   <= x <= ln2ovft:  cosh(x) := exp(x/2)/2 * exp(x/2)
31 
 *          ln2ovft  <  x           :  cosh(x) := huge*huge (overflow)
32 
 *
33 
 * Special cases:
34 
 *      cosh(x) is |x| if x is +INF, -INF, or NaN.
35 
 *      only cosh(0)=1 is exact for finite x.
36 
 */
37 
 
38 
#include "math.h"
39 
#include "math_private.h"
40 
 
41 
#ifdef __STDC__
42 
static const double one = 1.0, half=0.5, huge = 1.0e300;
43 
#else
44 
static double one = 1.0, half=0.5, huge = 1.0e300;
45 
#endif
46 
 
47 
#ifdef __STDC__
48 
        double __ieee754_cosh(double x)
49 
#else
50 
        double __ieee754_cosh(x)
51 
        double x;
52 
#endif
53 
{
54 
        double t,w;
55 
        int32_t ix;
56 
        u_int32_t lx;
57 
 
58 
    /* High word of |x|. */
59 
        GET_HIGH_WORD(ix,x);
60 
        ix &= 0x7fffffff;
61 
 
62 
    /* x is INF or NaN */
63 
        if(ix>=0x7ff00000) return x*x;
64 
 
65 
    /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
66 
        if(ix<0x3fd62e43) {
67 
            t = expm1(fabs(x));
68 
            w = one+t;
69 
            if (ix<0x3c800000) return w;        /* cosh(tiny) = 1 */
70 
            return one+(t*t)/(w+w);
71 
        }
72 
 
73 
    /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
74 
        if (ix < 0x40360000) {
75 
                t = __ieee754_exp(fabs(x));
76 
                return half*t+half/t;
77 
        }
78 
 
79 
    /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
80 
        if (ix < 0x40862E42)  return half*__ieee754_exp(fabs(x));
81 
 
82 
    /* |x| in [log(maxdouble), overflowthresold] */
83 
        GET_LOW_WORD(lx,x);
84 
        if (ix<0x408633CE ||
85 
              ((ix==0x408633ce)&&(lx<=(u_int32_t)0x8fb9f87d))) {
86 
            w = __ieee754_exp(half*fabs(x));
87 
            t = half*w;
88 
            return t*w;
89 
        }
90 
 
91 
    /* |x| > overflowthresold, cosh(x) overflow */
92 
        return huge*huge;
93 
}

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.