GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libm/src/s_cbrt.c Lines: 0 24 0.0 %
Date: 2017-11-13 Branches: 0 6 0.0 %

Line Branch Exec Source
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/* @(#)s_cbrt.c 5.1 93/09/24 */
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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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#include <float.h>
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#include <math.h>
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#include "math_private.h"
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/* cbrt(x)
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 * Return cube root of x
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 */
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static const u_int32_t
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	B1 = 715094163, /* B1 = (682-0.03306235651)*2**20 */
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	B2 = 696219795; /* B2 = (664-0.03306235651)*2**20 */
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static const double
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C =  5.42857142857142815906e-01, /* 19/35     = 0x3FE15F15, 0xF15F15F1 */
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D = -7.05306122448979611050e-01, /* -864/1225 = 0xBFE691DE, 0x2532C834 */
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E =  1.41428571428571436819e+00, /* 99/70     = 0x3FF6A0EA, 0x0EA0EA0F */
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F =  1.60714285714285720630e+00, /* 45/28     = 0x3FF9B6DB, 0x6DB6DB6E */
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G =  3.57142857142857150787e-01; /* 5/14      = 0x3FD6DB6D, 0xB6DB6DB7 */
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double
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cbrt(double x)
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{
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	int32_t	hx;
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	double r,s,t=0.0,w;
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	u_int32_t sign;
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	u_int32_t high,low;
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	GET_HIGH_WORD(hx,x);
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	sign=hx&0x80000000; 		/* sign= sign(x) */
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	hx  ^=sign;
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	if(hx>=0x7ff00000) return(x+x); /* cbrt(NaN,INF) is itself */
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	GET_LOW_WORD(low,x);
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	if((hx|low)==0)
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	    return(x);		/* cbrt(0) is itself */
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	SET_HIGH_WORD(x,hx);	/* x <- |x| */
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    /* rough cbrt to 5 bits */
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	if(hx<0x00100000) 		/* subnormal number */
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	  {SET_HIGH_WORD(t,0x43500000);	/* set t= 2**54 */
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	   t*=x; GET_HIGH_WORD(high,t); SET_HIGH_WORD(t,high/3+B2);
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	  }
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	else
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	  SET_HIGH_WORD(t,hx/3+B1);
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    /* new cbrt to 23 bits, may be implemented in single precision */
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	r=t*t/x;
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	s=C+r*t;
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	t*=G+F/(s+E+D/s);
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    /* chopped to 20 bits and make it larger than cbrt(x) */
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	GET_HIGH_WORD(high,t);
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	INSERT_WORDS(t,high+0x00000001,0);
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    /* one step newton iteration to 53 bits with error less than 0.667 ulps */
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	s=t*t;		/* t*t is exact */
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	r=x/s;
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	w=t+t;
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	r=(r-t)/(w+r);	/* r-s is exact */
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	t=t+t*r;
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    /* retore the sign bit */
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	GET_HIGH_WORD(high,t);
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	SET_HIGH_WORD(t,high|sign);
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	return(t);
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}
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DEF_STD(cbrt);
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LDBL_MAYBE_UNUSED_CLONE(cbrt);