gammln.c

来自「IBM(原)数据生成器和源代码」· C语言 代码 · 共 20 行

#include <math.h>

float gammln(float xx)
{
  double x,tmp,ser;
  static double cof[6]={76.18009173,-86.50532033,24.01409822,
			-1.231739516,0.120858003e-2,-0.536382e-5};
  int j;
  
  x=xx-1.0;
  tmp=x+5.5;
  tmp -= (x+0.5)*log(tmp);
  ser=1.0;
  for (j=0;j<=5;j++) {
    x += 1.0;
    ser += cof[j]/x;
  }
  return -tmp+log(2.50662827465*ser);
}