2023-05-03 01:35:25 +00:00
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/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
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2023-12-08 03:11:56 +00:00
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│ vi: set noet ft=c ts=8 tw=8 fenc=utf-8 :vi │
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2023-05-03 01:35:25 +00:00
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╚──────────────────────────────────────────────────────────────────────────────╝
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│ │
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│ Musl Libc │
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│ Copyright © 2005-2020 Rich Felker, et al. │
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│ │
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│ Permission is hereby granted, free of charge, to any person obtaining │
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│ a copy of this software and associated documentation files (the │
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│ "Software"), to deal in the Software without restriction, including │
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│ without limitation the rights to use, copy, modify, merge, publish, │
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│ distribute, sublicense, and/or sell copies of the Software, and to │
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│ permit persons to whom the Software is furnished to do so, subject to │
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│ the following conditions: │
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│ │
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│ The above copyright notice and this permission notice shall be │
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│ included in all copies or substantial portions of the Software. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, │
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│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF │
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│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. │
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│ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY │
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│ CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, │
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│ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE │
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│ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. │
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│ │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/math.h"
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asm(".ident\t\"\\n\\n\
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fdlibm (fdlibm license)\\n\
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Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\"");
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asm(".ident\t\"\\n\\n\
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Musl libc (MIT License)\\n\
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Copyright 2005-2014 Rich Felker, et. al.\"");
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asm(".include \"libc/disclaimer.inc\"");
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// clang-format off
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/* origin: FreeBSD /usr/src/lib/msun/src/s_cbrtf.c */
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/*
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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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* Debugged and optimized by Bruce D. Evans.
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*/
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/*
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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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static const unsigned
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B1 = 709958130, /* B1 = (127-127.0/3-0.03306235651)*2**23 */
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B2 = 642849266; /* B2 = (127-127.0/3-24/3-0.03306235651)*2**23 */
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/**
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* Returns cube root of 𝑥.
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*/
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float cbrtf(float x)
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{
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double_t r,T;
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union {float f; uint32_t i;} u = {x};
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uint32_t hx = u.i & 0x7fffffff;
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if (hx >= 0x7f800000) /* cbrt(NaN,INF) is itself */
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return x + x;
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/* rough cbrt to 5 bits */
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if (hx < 0x00800000) { /* zero or subnormal? */
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if (hx == 0)
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return x; /* cbrt(+-0) is itself */
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u.f = x*0x1p24f;
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hx = u.i & 0x7fffffff;
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hx = hx/3 + B2;
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} else
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hx = hx/3 + B1;
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u.i &= 0x80000000;
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u.i |= hx;
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/*
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* First step Newton iteration (solving t*t-x/t == 0) to 16 bits. In
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* double precision so that its terms can be arranged for efficiency
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* without causing overflow or underflow.
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*/
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T = u.f;
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r = T*T*T;
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T = T*((double_t)x+x+r)/(x+r+r);
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/*
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* Second step Newton iteration to 47 bits. In double precision for
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* efficiency and accuracy.
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*/
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r = T*T*T;
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T = T*((double_t)x+x+r)/(x+r+r);
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/* rounding to 24 bits is perfect in round-to-nearest mode */
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return T;
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}
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