mirror of
https://github.com/fluencelabs/musl
synced 2025-06-10 13:31:37 +00:00
0cbb654791
zero, one, two, half are replaced by const literals The policy was to use the f suffix for float consts (1.0f), but don't use suffix for long double consts (these consts can be exactly represented as double).
55 lines
1.5 KiB
C
55 lines
1.5 KiB
C
/* origin: FreeBSD /usr/src/lib/msun/src/e_acosh.c */
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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 SunSoft, 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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*/
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/* acosh(x)
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* Method :
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* Based on
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* acosh(x) = log [ x + sqrt(x*x-1) ]
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* we have
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* acosh(x) := log(x)+ln2, if x is large; else
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* acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else
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* acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1.
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*
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* Special cases:
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* acosh(x) is NaN with signal if x<1.
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* acosh(NaN) is NaN without signal.
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*/
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#include "libm.h"
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static const double
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ln2 = 6.93147180559945286227e-01; /* 0x3FE62E42, 0xFEFA39EF */
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double acosh(double x)
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{
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double t;
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int32_t hx;
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uint32_t lx;
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EXTRACT_WORDS(hx, lx, x);
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if (hx < 0x3ff00000) { /* x < 1 */
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return (x-x)/(x-x);
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} else if (hx >= 0x41b00000) { /* x > 2**28 */
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if (hx >= 0x7ff00000) /* x is inf of NaN */
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return x+x;
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return log(x) + ln2; /* acosh(huge) = log(2x) */
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} else if ((hx-0x3ff00000 | lx) == 0) {
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return 0.0; /* acosh(1) = 0 */
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} else if (hx > 0x40000000) { /* 2**28 > x > 2 */
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t = x*x;
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return log(2.0*x - 1.0/(x+sqrt(t-1.0)));
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} else { /* 1 < x < 2 */
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t = x-1.0;
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return log1p(t + sqrt(2.0*t+t*t));
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}
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}
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