diff options
Diffstat (limited to 'lib/mlibc/options/ansi/musl-generic-math/log10.c')
-rw-r--r-- | lib/mlibc/options/ansi/musl-generic-math/log10.c | 101 |
1 files changed, 0 insertions, 101 deletions
diff --git a/lib/mlibc/options/ansi/musl-generic-math/log10.c b/lib/mlibc/options/ansi/musl-generic-math/log10.c deleted file mode 100644 index 8102687..0000000 --- a/lib/mlibc/options/ansi/musl-generic-math/log10.c +++ /dev/null @@ -1,101 +0,0 @@ -/* origin: FreeBSD /usr/src/lib/msun/src/e_log10.c */ -/* - * ==================================================== - * 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. - * ==================================================== - */ -/* - * Return the base 10 logarithm of x. See log.c for most comments. - * - * Reduce x to 2^k (1+f) and calculate r = log(1+f) - f + f*f/2 - * as in log.c, then combine and scale in extra precision: - * log10(x) = (f - f*f/2 + r)/log(10) + k*log10(2) - */ - -#include <math.h> -#include <stdint.h> - -static const double -ivln10hi = 4.34294481878168880939e-01, /* 0x3fdbcb7b, 0x15200000 */ -ivln10lo = 2.50829467116452752298e-11, /* 0x3dbb9438, 0xca9aadd5 */ -log10_2hi = 3.01029995663611771306e-01, /* 0x3FD34413, 0x509F6000 */ -log10_2lo = 3.69423907715893078616e-13, /* 0x3D59FEF3, 0x11F12B36 */ -Lg1 = 6.666666666666735130e-01, /* 3FE55555 55555593 */ -Lg2 = 3.999999999940941908e-01, /* 3FD99999 9997FA04 */ -Lg3 = 2.857142874366239149e-01, /* 3FD24924 94229359 */ -Lg4 = 2.222219843214978396e-01, /* 3FCC71C5 1D8E78AF */ -Lg5 = 1.818357216161805012e-01, /* 3FC74664 96CB03DE */ -Lg6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */ -Lg7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */ - -double log10(double x) -{ - union {double f; uint64_t i;} u = {x}; - double_t hfsq,f,s,z,R,w,t1,t2,dk,y,hi,lo,val_hi,val_lo; - uint32_t hx; - int k; - - hx = u.i>>32; - k = 0; - if (hx < 0x00100000 || hx>>31) { - if (u.i<<1 == 0) - return -1/(x*x); /* log(+-0)=-inf */ - if (hx>>31) - return (x-x)/0.0; /* log(-#) = NaN */ - /* subnormal number, scale x up */ - k -= 54; - x *= 0x1p54; - u.f = x; - hx = u.i>>32; - } else if (hx >= 0x7ff00000) { - return x; - } else if (hx == 0x3ff00000 && u.i<<32 == 0) - return 0; - - /* reduce x into [sqrt(2)/2, sqrt(2)] */ - hx += 0x3ff00000 - 0x3fe6a09e; - k += (int)(hx>>20) - 0x3ff; - hx = (hx&0x000fffff) + 0x3fe6a09e; - u.i = (uint64_t)hx<<32 | (u.i&0xffffffff); - x = u.f; - - f = x - 1.0; - hfsq = 0.5*f*f; - s = f/(2.0+f); - z = s*s; - w = z*z; - t1 = w*(Lg2+w*(Lg4+w*Lg6)); - t2 = z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7))); - R = t2 + t1; - - /* See log2.c for details. */ - /* hi+lo = f - hfsq + s*(hfsq+R) ~ log(1+f) */ - hi = f - hfsq; - u.f = hi; - u.i &= (uint64_t)-1<<32; - hi = u.f; - lo = f - hi - hfsq + s*(hfsq+R); - - /* val_hi+val_lo ~ log10(1+f) + k*log10(2) */ - val_hi = hi*ivln10hi; - dk = k; - y = dk*log10_2hi; - val_lo = dk*log10_2lo + (lo+hi)*ivln10lo + lo*ivln10hi; - - /* - * Extra precision in for adding y is not strictly needed - * since there is no very large cancellation near x = sqrt(2) or - * x = 1/sqrt(2), but we do it anyway since it costs little on CPUs - * with some parallelism and it reduces the error for many args. - */ - w = y + val_hi; - val_lo += (y - w) + val_hi; - val_hi = w; - - return val_lo + val_hi; -} |