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Diffstat (limited to 'src/math/e_log10.c')
-rw-r--r-- | src/math/e_log10.c | 83 |
1 files changed, 0 insertions, 83 deletions
diff --git a/src/math/e_log10.c b/src/math/e_log10.c deleted file mode 100644 index 3be179f7..00000000 --- a/src/math/e_log10.c +++ /dev/null @@ -1,83 +0,0 @@ - -/* @(#)e_log10.c 1.3 95/01/18 */ -/* - * ==================================================== - * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. - * - * Developed at SunSoft, a Sun Microsystems, Inc. business. - * Permission to use, copy, modify, and distribute this - * software is freely granted, provided that this notice - * is preserved. - * ==================================================== - */ - -/* log10(x) - * Return the base 10 logarithm of x - * - * Method : - * Let log10_2hi = leading 40 bits of log10(2) and - * log10_2lo = log10(2) - log10_2hi, - * ivln10 = 1/log(10) rounded. - * Then - * n = ilogb(x), - * if(n<0) n = n+1; - * x = scalbn(x,-n); - * log10(x) := n*log10_2hi + (n*log10_2lo + ivln10*log(x)) - * - * Note 1: - * To guarantee log10(10**n)=n, where 10**n is normal, the rounding - * mode must set to Round-to-Nearest. - * Note 2: - * [1/log(10)] rounded to 53 bits has error .198 ulps; - * log10 is monotonic at all binary break points. - * - * Special cases: - * log10(x) is NaN with signal if x < 0; - * log10(+INF) is +INF with no signal; log10(0) is -INF with signal; - * log10(NaN) is that NaN with no signal; - * log10(10**N) = N for N=0,1,...,22. - * - * Constants: - * The hexadecimal values are the intended ones for the following constants. - * The decimal values may be used, provided that the compiler will convert - * from decimal to binary accurately enough to produce the hexadecimal values - * shown. - */ - -#include <math.h> -#include "math_private.h" - -static const double -two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ -ivln10 = 4.34294481903251816668e-01, /* 0x3FDBCB7B, 0x1526E50E */ -log10_2hi = 3.01029995663611771306e-01, /* 0x3FD34413, 0x509F6000 */ -log10_2lo = 3.69423907715893078616e-13; /* 0x3D59FEF3, 0x11F12B36 */ - -static const double zero = 0.0; - -double -log10(double x) -{ - double y,z; - int32_t i,k,hx; - uint32_t lx; - - EXTRACT_WORDS(hx,lx,x); - - k=0; - if (hx < 0x00100000) { /* x < 2**-1022 */ - if (((hx&0x7fffffff)|lx)==0) - return -two54/zero; /* log(+-0)=-inf */ - if (hx<0) return (x-x)/zero; /* log(-#) = NaN */ - k -= 54; x *= two54; /* subnormal number, scale up x */ - GET_HIGH_WORD(hx,x); - } - if (hx >= 0x7ff00000) return x+x; - k += (hx>>20)-1023; - i = ((uint32_t)k&0x80000000)>>31; - hx = (hx&0x000fffff)|((0x3ff-i)<<20); - y = (double)(k+i); - SET_HIGH_WORD(x,hx); - z = y*log10_2lo + ivln10*log(x); - return z+y*log10_2hi; -} |