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Diffstat (limited to 'libm/double/rgamma.c')
| -rw-r--r-- | libm/double/rgamma.c | 209 |
1 files changed, 0 insertions, 209 deletions
diff --git a/libm/double/rgamma.c b/libm/double/rgamma.c deleted file mode 100644 index 1d6ff3840..000000000 --- a/libm/double/rgamma.c +++ /dev/null @@ -1,209 +0,0 @@ -/* rgamma.c - * - * Reciprocal gamma function - * - * - * - * SYNOPSIS: - * - * double x, y, rgamma(); - * - * y = rgamma( x ); - * - * - * - * DESCRIPTION: - * - * Returns one divided by the gamma function of the argument. - * - * The function is approximated by a Chebyshev expansion in - * the interval [0,1]. Range reduction is by recurrence - * for arguments between -34.034 and +34.84425627277176174. - * 1/MAXNUM is returned for positive arguments outside this - * range. For arguments less than -34.034 the cosecant - * reflection formula is applied; lograrithms are employed - * to avoid unnecessary overflow. - * - * The reciprocal gamma function has no singularities, - * but overflow and underflow may occur for large arguments. - * These conditions return either MAXNUM or 1/MAXNUM with - * appropriate sign. - * - * ACCURACY: - * - * Relative error: - * arithmetic domain # trials peak rms - * DEC -30,+30 4000 1.2e-16 1.8e-17 - * IEEE -30,+30 30000 1.1e-15 2.0e-16 - * For arguments less than -34.034 the peak error is on the - * order of 5e-15 (DEC), excepting overflow or underflow. - */ - -/* -Cephes Math Library Release 2.8: June, 2000 -Copyright 1985, 1987, 2000 by Stephen L. Moshier -*/ - -#include <math.h> - -/* Chebyshev coefficients for reciprocal gamma function - * in interval 0 to 1. Function is 1/(x gamma(x)) - 1 - */ - -#ifdef UNK -static double R[] = { - 3.13173458231230000000E-17, --6.70718606477908000000E-16, - 2.20039078172259550000E-15, - 2.47691630348254132600E-13, --6.60074100411295197440E-12, - 5.13850186324226978840E-11, - 1.08965386454418662084E-9, --3.33964630686836942556E-8, - 2.68975996440595483619E-7, - 2.96001177518801696639E-6, --8.04814124978471142852E-5, - 4.16609138709688864714E-4, - 5.06579864028608725080E-3, --6.41925436109158228810E-2, --4.98558728684003594785E-3, - 1.27546015610523951063E-1 -}; -#endif - -#ifdef DEC -static unsigned short R[] = { -0022420,0066376,0176751,0071636, -0123501,0051114,0042104,0131153, -0024036,0107013,0126504,0033361, -0025613,0070040,0035174,0162316, -0126750,0037060,0077775,0122202, -0027541,0177143,0037675,0105150, -0030625,0141311,0075005,0115436, -0132017,0067714,0125033,0014721, -0032620,0063707,0105256,0152643, -0033506,0122235,0072757,0170053, -0134650,0144041,0015617,0016143, -0035332,0066125,0000776,0006215, -0036245,0177377,0137173,0131432, -0137203,0073541,0055645,0141150, -0136243,0057043,0026226,0017362, -0037402,0115554,0033441,0012310 -}; -#endif - -#ifdef IBMPC -static unsigned short R[] = { -0x2e74,0xdfbd,0x0d9f,0x3c82, -0x964d,0x8888,0x2a49,0xbcc8, -0x86de,0x75a8,0xd1c1,0x3ce3, -0x9c9a,0x074f,0x6e04,0x3d51, -0xb490,0x0fff,0x07c6,0xbd9d, -0xb14d,0x67f7,0x3fcc,0x3dcc, -0xb364,0x2f40,0xb859,0x3e12, -0x633a,0x9543,0xedf9,0xbe61, -0xdab4,0xf155,0x0cf8,0x3e92, -0xfe05,0xaebd,0xd493,0x3ec8, -0xe38c,0x2371,0x1904,0xbf15, -0xc192,0xa03f,0x4d8a,0x3f3b, -0x7663,0xf7cf,0xbfdf,0x3f74, -0xb84d,0x2b74,0x6eec,0xbfb0, -0xc3de,0x6592,0x6bc4,0xbf74, -0x2299,0x86e4,0x536d,0x3fc0 -}; -#endif - -#ifdef MIEEE -static unsigned short R[] = { -0x3c82,0x0d9f,0xdfbd,0x2e74, -0xbcc8,0x2a49,0x8888,0x964d, -0x3ce3,0xd1c1,0x75a8,0x86de, -0x3d51,0x6e04,0x074f,0x9c9a, -0xbd9d,0x07c6,0x0fff,0xb490, -0x3dcc,0x3fcc,0x67f7,0xb14d, -0x3e12,0xb859,0x2f40,0xb364, -0xbe61,0xedf9,0x9543,0x633a, -0x3e92,0x0cf8,0xf155,0xdab4, -0x3ec8,0xd493,0xaebd,0xfe05, -0xbf15,0x1904,0x2371,0xe38c, -0x3f3b,0x4d8a,0xa03f,0xc192, -0x3f74,0xbfdf,0xf7cf,0x7663, -0xbfb0,0x6eec,0x2b74,0xb84d, -0xbf74,0x6bc4,0x6592,0xc3de, -0x3fc0,0x536d,0x86e4,0x2299 -}; -#endif - -static char name[] = "rgamma"; - -#ifdef ANSIPROT -extern double chbevl ( double, void *, int ); -extern double exp ( double ); -extern double log ( double ); -extern double sin ( double ); -extern double lgam ( double ); -#else -double chbevl(), exp(), log(), sin(), lgam(); -#endif -extern double PI, MAXLOG, MAXNUM; - - -double rgamma(x) -double x; -{ -double w, y, z; -int sign; - -if( x > 34.84425627277176174) - { - mtherr( name, UNDERFLOW ); - return(1.0/MAXNUM); - } -if( x < -34.034 ) - { - w = -x; - z = sin( PI*w ); - if( z == 0.0 ) - return(0.0); - if( z < 0.0 ) - { - sign = 1; - z = -z; - } - else - sign = -1; - - y = log( w * z ) - log(PI) + lgam(w); - if( y < -MAXLOG ) - { - mtherr( name, UNDERFLOW ); - return( sign * 1.0 / MAXNUM ); - } - if( y > MAXLOG ) - { - mtherr( name, OVERFLOW ); - return( sign * MAXNUM ); - } - return( sign * exp(y)); - } -z = 1.0; -w = x; - -while( w > 1.0 ) /* Downward recurrence */ - { - w -= 1.0; - z *= w; - } -while( w < 0.0 ) /* Upward recurrence */ - { - z /= w; - w += 1.0; - } -if( w == 0.0 ) /* Nonpositive integer */ - return(0.0); -if( w == 1.0 ) /* Other integer */ - return( 1.0/z ); - -y = w * ( 1.0 + chbevl( 4.0*w-2.0, R, 16 ) ) / z; -return(y); -} |