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authorIan Moffett <ian@osmora.org>2024-03-07 17:28:52 -0500
committerIan Moffett <ian@osmora.org>2024-03-07 18:24:51 -0500
commitf5e48e94a2f4d4bbd6e5628c7f2afafc6dbcc459 (patch)
tree93b156621dc0303816b37f60ba88051b702d92f6 /lib/mlibc/options/ansi/musl-generic-math/log.c
parentbd5969fc876a10b18613302db7087ef3c40f18e1 (diff)
build: Build mlibc + add distclean target
Signed-off-by: Ian Moffett <ian@osmora.org>
Diffstat (limited to 'lib/mlibc/options/ansi/musl-generic-math/log.c')
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1 files changed, 0 insertions, 118 deletions
diff --git a/lib/mlibc/options/ansi/musl-generic-math/log.c b/lib/mlibc/options/ansi/musl-generic-math/log.c
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--- a/lib/mlibc/options/ansi/musl-generic-math/log.c
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@@ -1,118 +0,0 @@
-/* origin: FreeBSD /usr/src/lib/msun/src/e_log.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.
- * ====================================================
- */
-/* log(x)
- * Return the logarithm of x
- *
- * Method :
- * 1. Argument Reduction: find k and f such that
- * x = 2^k * (1+f),
- * where sqrt(2)/2 < 1+f < sqrt(2) .
- *
- * 2. Approximation of log(1+f).
- * Let s = f/(2+f) ; based on log(1+f) = log(1+s) - log(1-s)
- * = 2s + 2/3 s**3 + 2/5 s**5 + .....,
- * = 2s + s*R
- * We use a special Remez algorithm on [0,0.1716] to generate
- * a polynomial of degree 14 to approximate R The maximum error
- * of this polynomial approximation is bounded by 2**-58.45. In
- * other words,
- * 2 4 6 8 10 12 14
- * R(z) ~ Lg1*s +Lg2*s +Lg3*s +Lg4*s +Lg5*s +Lg6*s +Lg7*s
- * (the values of Lg1 to Lg7 are listed in the program)
- * and
- * | 2 14 | -58.45
- * | Lg1*s +...+Lg7*s - R(z) | <= 2
- * | |
- * Note that 2s = f - s*f = f - hfsq + s*hfsq, where hfsq = f*f/2.
- * In order to guarantee error in log below 1ulp, we compute log
- * by
- * log(1+f) = f - s*(f - R) (if f is not too large)
- * log(1+f) = f - (hfsq - s*(hfsq+R)). (better accuracy)
- *
- * 3. Finally, log(x) = k*ln2 + log(1+f).
- * = k*ln2_hi+(f-(hfsq-(s*(hfsq+R)+k*ln2_lo)))
- * Here ln2 is split into two floating point number:
- * ln2_hi + ln2_lo,
- * where n*ln2_hi is always exact for |n| < 2000.
- *
- * Special cases:
- * log(x) is NaN with signal if x < 0 (including -INF) ;
- * log(+INF) is +INF; log(0) is -INF with signal;
- * log(NaN) is that NaN with no signal.
- *
- * Accuracy:
- * according to an error analysis, the error is always less than
- * 1 ulp (unit in the last place).
- *
- * 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 <stdint.h>
-
-static const double
-ln2_hi = 6.93147180369123816490e-01, /* 3fe62e42 fee00000 */
-ln2_lo = 1.90821492927058770002e-10, /* 3dea39ef 35793c76 */
-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 log(double x)
-{
- union {double f; uint64_t i;} u = {x};
- double_t hfsq,f,s,z,R,w,t1,t2,dk;
- 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;
- dk = k;
- return s*(hfsq+R) + dk*ln2_lo - hfsq + f + dk*ln2_hi;
-}