1*05a0b428SJohn Marino /* e_coshf.c -- float version of e_cosh.c.
2*05a0b428SJohn Marino * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3*05a0b428SJohn Marino */
4*05a0b428SJohn Marino
5*05a0b428SJohn Marino /*
6*05a0b428SJohn Marino * ====================================================
7*05a0b428SJohn Marino * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8*05a0b428SJohn Marino *
9*05a0b428SJohn Marino * Developed at SunPro, a Sun Microsystems, Inc. business.
10*05a0b428SJohn Marino * Permission to use, copy, modify, and distribute this
11*05a0b428SJohn Marino * software is freely granted, provided that this notice
12*05a0b428SJohn Marino * is preserved.
13*05a0b428SJohn Marino * ====================================================
14*05a0b428SJohn Marino */
15*05a0b428SJohn Marino
16*05a0b428SJohn Marino #include "math.h"
17*05a0b428SJohn Marino #include "math_private.h"
18*05a0b428SJohn Marino
19*05a0b428SJohn Marino static const volatile float huge = 1.0e30;
20*05a0b428SJohn Marino static const float one = 1.0, half=0.5;
21*05a0b428SJohn Marino
22*05a0b428SJohn Marino float
coshf(float x)23*05a0b428SJohn Marino coshf(float x)
24*05a0b428SJohn Marino {
25*05a0b428SJohn Marino float t,w;
26*05a0b428SJohn Marino int32_t ix;
27*05a0b428SJohn Marino
28*05a0b428SJohn Marino GET_FLOAT_WORD(ix,x);
29*05a0b428SJohn Marino ix &= 0x7fffffff;
30*05a0b428SJohn Marino
31*05a0b428SJohn Marino /* x is INF or NaN */
32*05a0b428SJohn Marino if(ix>=0x7f800000) return x*x;
33*05a0b428SJohn Marino
34*05a0b428SJohn Marino /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
35*05a0b428SJohn Marino if(ix<0x3eb17218) {
36*05a0b428SJohn Marino t = expm1f(fabsf(x));
37*05a0b428SJohn Marino w = one+t;
38*05a0b428SJohn Marino if (ix<0x24000000) return w; /* cosh(tiny) = 1 */
39*05a0b428SJohn Marino return one+(t*t)/(w+w);
40*05a0b428SJohn Marino }
41*05a0b428SJohn Marino
42*05a0b428SJohn Marino /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
43*05a0b428SJohn Marino if (ix < 0x41b00000) {
44*05a0b428SJohn Marino t = expf(fabsf(x));
45*05a0b428SJohn Marino return half*t+half/t;
46*05a0b428SJohn Marino }
47*05a0b428SJohn Marino
48*05a0b428SJohn Marino /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
49*05a0b428SJohn Marino if (ix < 0x42b17180) return half*expf(fabsf(x));
50*05a0b428SJohn Marino
51*05a0b428SJohn Marino /* |x| in [log(maxdouble), overflowthresold] */
52*05a0b428SJohn Marino if (ix<=0x42b2d4fc) {
53*05a0b428SJohn Marino w = expf(half*fabsf(x));
54*05a0b428SJohn Marino t = half*w;
55*05a0b428SJohn Marino return t*w;
56*05a0b428SJohn Marino }
57*05a0b428SJohn Marino
58*05a0b428SJohn Marino /* |x| > overflowthresold, cosh(x) overflow */
59*05a0b428SJohn Marino return huge*huge;
60*05a0b428SJohn Marino }
61