k_logf.h

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/*
 * ====================================================
 * 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 "../inc/cdefs-compat.h"
//__FBSDID("$FreeBSD: src/lib/msun/src/k_logf.h,v 1.3 2011/10/15 05:23:28 das Exp $");
 
/*
 * 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 = 0.66666662693f,   /* 0.66666662693 */
Lg2 = 0.40000972152f,   /* 0.40000972152 */
Lg3 = 0.28498786688f,   /* 0.28498786688 */
Lg4 = 0.24279078841f;   /* 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);
}