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