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[/] [scarts/] [trunk/] [toolchain/] [scarts-gcc/] [gcc-4.1.1/] [gcc/] [testsuite/] [gcc.c-torture/] [execute/] [cbrt.c] - Rev 12
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/* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunPro, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ #ifndef __vax__ static const unsigned long B1 = 715094163, /* B1 = (682-0.03306235651)*2**20 */ B2 = 696219795; /* B2 = (664-0.03306235651)*2**20 */ static const double C = 5.42857142857142815906e-01, /* 19/35 = 0x3FE15F15, 0xF15F15F1 */ D = -7.05306122448979611050e-01, /* -864/1225 = 0xBFE691DE, 0x2532C834 */ E = 1.41428571428571436819e+00, /* 99/70 = 0x3FF6A0EA, 0x0EA0EA0F */ F = 1.60714285714285720630e+00, /* 45/28 = 0x3FF9B6DB, 0x6DB6DB6E */ G = 3.57142857142857150787e-01; /* 5/14 = 0x3FD6DB6D, 0xB6DB6DB7 */ double cbrtl (double x) { long hx; double r,s,w; double lt; unsigned sign; typedef unsigned unsigned32 __attribute__((mode(SI))); union { double t; unsigned32 pt[2]; } ut, ux; int n0; ut.t = 1.0; n0 = (ut.pt[0] == 0); ut.t = 0.0; ux.t = x; hx = ux.pt[n0]; /* high word of x */ sign=hx&0x80000000; /* sign= sign(x) */ hx ^=sign; if(hx>=0x7ff00000) return(x+x); /* cbrt(NaN,INF) is itself */ if((hx| ux.pt[1-n0])==0) return(ux.t); /* cbrt(0) is itself */ ux.pt[n0] = hx; /* rough cbrt to 5 bits */ if(hx<0x00100000) /* subnormal number */ {ut.pt[n0]=0x43500000; /* set t= 2**54 */ ut.t*=x; ut.pt[n0]=ut.pt[n0]/3+B2; } else ut.pt[n0]=hx/3+B1; /* new cbrt to 23 bits, may be implemented in single precision */ r=ut.t*ut.t/ux.t; s=C+r*ut.t; ut.t*=G+F/(s+E+D/s); /* chopped to 20 bits and make it larger than cbrt(x) */ ut.pt[1-n0]=0; ut.pt[n0]+=0x00000001; /* one step newton iteration to 53 bits with error less than 0.667 ulps */ s=ut.t*ut.t; /* t*t is exact */ r=ux.t/s; w=ut.t+ut.t; r=(r-ut.t)/(w+r); /* r-s is exact */ ut.t=ut.t+ut.t*r; /* restore the sign bit */ ut.pt[n0] |= sign; lt = ut.t; lt -= (lt - (x/(lt*lt))) * 0.333333333333333333333; return lt; } main () { if ((int) (cbrtl (27.0) + 0.5) != 3) abort (); exit (0); } #else main () { exit (0); } #endif