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Diffstat (limited to 'trunk/missing/lgamma_r.c')
-rw-r--r-- | trunk/missing/lgamma_r.c | 68 |
1 files changed, 0 insertions, 68 deletions
diff --git a/trunk/missing/lgamma_r.c b/trunk/missing/lgamma_r.c deleted file mode 100644 index ba8535b18a..0000000000 --- a/trunk/missing/lgamma_r.c +++ /dev/null @@ -1,68 +0,0 @@ -/* lgamma_r.c - public domain implementation of function lgamma_r(3m) - -lgamma_r() is based on gamma(). modified by Tanaka Akira. - -reference - Haruhiko Okumura: C-gengo niyoru saishin algorithm jiten - (New Algorithm handbook in C language) (Gijyutsu hyouron - sha, Tokyo, 1991) [in Japanese] - http://oku.edu.mie-u.ac.jp/~okumura/algo/ -*/ - -/*********************************************************** - gamma.c -- Gamma function -***********************************************************/ -#include <math.h> -#include <errno.h> -#define PI 3.14159265358979324 /* $\pi$ */ -#define LOG_2PI 1.83787706640934548 /* $\log 2\pi$ */ -#define LOG_PI 1.14472988584940017 /* $\log_e \pi$ */ -#define N 8 - -#define B0 1 /* Bernoulli numbers */ -#define B1 (-1.0 / 2.0) -#define B2 ( 1.0 / 6.0) -#define B4 (-1.0 / 30.0) -#define B6 ( 1.0 / 42.0) -#define B8 (-1.0 / 30.0) -#define B10 ( 5.0 / 66.0) -#define B12 (-691.0 / 2730.0) -#define B14 ( 7.0 / 6.0) -#define B16 (-3617.0 / 510.0) - -static double -loggamma(double x) /* the natural logarithm of the Gamma function. */ -{ - double v, w; - - if (x == 1.0 || x == 2.0) return 0.0; - - v = 1; - while (x < N) { v *= x; x++; } - w = 1 / (x * x); - return ((((((((B16 / (16 * 15)) * w + (B14 / (14 * 13))) * w - + (B12 / (12 * 11))) * w + (B10 / (10 * 9))) * w - + (B8 / ( 8 * 7))) * w + (B6 / ( 6 * 5))) * w - + (B4 / ( 4 * 3))) * w + (B2 / ( 2 * 1))) / x - + 0.5 * LOG_2PI - log(v) - x + (x - 0.5) * log(x); -} - -/* the natural logarithm of the absolute value of the Gamma function */ -double -lgamma_r(double x, int *signp) -{ - if (x <= 0) { - double i, f, s; - f = modf(-x, &i); - if (f == 0.0) { /* pole error */ - *signp = 1; - errno = ERANGE; - return HUGE_VAL; - } - *signp = (fmod(i, 2.0) != 0.0) ? 1 : -1; - s = sin(PI * f); - if (s < 0) s = -s; - return LOG_PI - log(s) - loggamma(1 - x); - } - *signp = 1; - return loggamma(x); -} |