| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| #include <sys/cdefs.h> |
| __FBSDID("$FreeBSD$"); |
| |
| /* |
| * Float version of k_log.h. See the latter for most comments. |
| */ |
| |
| static const float |
| /* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */ |
| Lg1 = 0xaaaaaa.0p-24, /* 0.66666662693 */ |
| Lg2 = 0xccce13.0p-25, /* 0.40000972152 */ |
| Lg3 = 0x91e9ee.0p-25, /* 0.28498786688 */ |
| Lg4 = 0xf89e26.0p-26; /* 0.24279078841 */ |
| |
| static inline float |
| k_log1pf(float f) |
| { |
| float hfsq,s,z,R,w,t1,t2; |
| |
| s = f/((float)2.0+f); |
| z = s*s; |
| w = z*z; |
| t1= w*(Lg2+w*Lg4); |
| t2= z*(Lg1+w*Lg3); |
| R = t2+t1; |
| hfsq=(float)0.5*f*f; |
| return s*(hfsq+R); |
| } |