1/*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 */
11
12/*
13 * Float version of k_log.h.  See the latter for most comments.
14 */
15
16static const float
17/* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
18Lg1 =      0xaaaaaa.0p-24,	/* 0.66666662693 */
19Lg2 =      0xccce13.0p-25,	/* 0.40000972152 */
20Lg3 =      0x91e9ee.0p-25,	/* 0.28498786688 */
21Lg4 =      0xf89e26.0p-26;	/* 0.24279078841 */
22
23static inline float
24k_log1pf(float f)
25{
26	float hfsq,s,z,R,w,t1,t2;
27
28 	s = f/((float)2.0+f);
29	z = s*s;
30	w = z*z;
31	t1= w*(Lg2+w*Lg4);
32	t2= z*(Lg1+w*Lg3);
33	R = t2+t1;
34	hfsq=(float)0.5*f*f;
35	return s*(hfsq+R);
36}
37