From 7ce331c01ce6eb7b3f5c715a38a24359da9c6ee2 Mon Sep 17 00:00:00 2001 From: Eric Andersen Date: Thu, 22 Nov 2001 14:04:29 +0000 Subject: Totally rework the math library, this time based on the MacOs X math library (which is itself based on the math lib from FreeBSD). -Erik --- libm/double/cbrt.c | 142 ----------------------------------------------------- 1 file changed, 142 deletions(-) delete mode 100644 libm/double/cbrt.c (limited to 'libm/double/cbrt.c') diff --git a/libm/double/cbrt.c b/libm/double/cbrt.c deleted file mode 100644 index 026207275..000000000 --- a/libm/double/cbrt.c +++ /dev/null @@ -1,142 +0,0 @@ -/* cbrt.c - * - * Cube root - * - * - * - * SYNOPSIS: - * - * double x, y, cbrt(); - * - * y = cbrt( x ); - * - * - * - * DESCRIPTION: - * - * Returns the cube root of the argument, which may be negative. - * - * Range reduction involves determining the power of 2 of - * the argument. A polynomial of degree 2 applied to the - * mantissa, and multiplication by the cube root of 1, 2, or 4 - * approximates the root to within about 0.1%. Then Newton's - * iteration is used three times to converge to an accurate - * result. - * - * - * - * ACCURACY: - * - * Relative error: - * arithmetic domain # trials peak rms - * DEC -10,10 200000 1.8e-17 6.2e-18 - * IEEE 0,1e308 30000 1.5e-16 5.0e-17 - * - */ - /* cbrt.c */ - -/* -Cephes Math Library Release 2.8: June, 2000 -Copyright 1984, 1991, 2000 by Stephen L. Moshier -*/ - - -#include - -static double CBRT2 = 1.2599210498948731647672; -static double CBRT4 = 1.5874010519681994747517; -static double CBRT2I = 0.79370052598409973737585; -static double CBRT4I = 0.62996052494743658238361; - -#ifdef ANSIPROT -extern double frexp ( double, int * ); -extern double ldexp ( double, int ); -extern int isnan ( double ); -extern int isfinite ( double ); -#else -double frexp(), ldexp(); -int isnan(), isfinite(); -#endif - -double cbrt(x) -double x; -{ -int e, rem, sign; -double z; - -#ifdef NANS -if( isnan(x) ) - return x; -#endif -#ifdef INFINITIES -if( !isfinite(x) ) - return x; -#endif -if( x == 0 ) - return( x ); -if( x > 0 ) - sign = 1; -else - { - sign = -1; - x = -x; - } - -z = x; -/* extract power of 2, leaving - * mantissa between 0.5 and 1 - */ -x = frexp( x, &e ); - -/* Approximate cube root of number between .5 and 1, - * peak relative error = 9.2e-6 - */ -x = (((-1.3466110473359520655053e-1 * x - + 5.4664601366395524503440e-1) * x - - 9.5438224771509446525043e-1) * x - + 1.1399983354717293273738e0 ) * x - + 4.0238979564544752126924e-1; - -/* exponent divided by 3 */ -if( e >= 0 ) - { - rem = e; - e /= 3; - rem -= 3*e; - if( rem == 1 ) - x *= CBRT2; - else if( rem == 2 ) - x *= CBRT4; - } - - -/* argument less than 1 */ - -else - { - e = -e; - rem = e; - e /= 3; - rem -= 3*e; - if( rem == 1 ) - x *= CBRT2I; - else if( rem == 2 ) - x *= CBRT4I; - e = -e; - } - -/* multiply by power of 2 */ -x = ldexp( x, e ); - -/* Newton iteration */ -x -= ( x - (z/(x*x)) )*0.33333333333333333333; -#ifdef DEC -x -= ( x - (z/(x*x)) )/3.0; -#else -x -= ( x - (z/(x*x)) )*0.33333333333333333333; -#endif - -if( sign < 0 ) - x = -x; -return(x); -} -- cgit v1.2.3