40 lines
1.0 KiB
C
40 lines
1.0 KiB
C
/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#include "cdefs-compat.h"
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//__FBSDID("$FreeBSD: src/lib/msun/src/k_logf.h,v 1.3 2011/10/15 05:23:28 das Exp $");
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/*
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* Float version of k_log.h. See the latter for most comments.
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*/
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static const float
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/* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
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Lg1 = 0xaaaaaa.0p-24, /* 0.66666662693 */
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Lg2 = 0xccce13.0p-25, /* 0.40000972152 */
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Lg3 = 0x91e9ee.0p-25, /* 0.28498786688 */
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Lg4 = 0xf89e26.0p-26; /* 0.24279078841 */
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static inline float
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k_log1pf(float f)
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{
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float hfsq,s,z,R,w,t1,t2;
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s = f/((float)2.0+f);
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z = s*s;
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w = z*z;
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t1= w*(Lg2+w*Lg4);
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t2= z*(Lg1+w*Lg3);
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R = t2+t1;
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hfsq=(float)0.5*f*f;
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return s*(hfsq+R);
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}
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