qromb.c

来自「Numerical Recipes Software 提供的算法子程序集」· C语言 代码 · 共 35 行

#include <math.h>
#define EPS 1.0e-6
#define JMAX 20
#define JMAXP (JMAX+1)
#define K 5

float qromb(func,a,b)
float (*func)(),a,b;
{
	float trapzd();
	void polint();
	void nrerror();
	float ss,dss;
	float s[JMAXP+1],h[JMAXP+1];
	int j;

	h[1]=1.0;
	for (j=1;j<=JMAX;j++) {
		s[j]=trapzd(func,a,b,j);
		if (j >= K) {
			polint(&h[j-K],&s[j-K],K,0.0,&ss,&dss);
			if (fabs(dss) <= EPS*fabs(ss)) return ss;
		}
		s[j+1]=s[j];
		h[j+1]=0.25*h[j];
	}
	nrerror("Too many steps in routine qromb");
	return 0.0;
}
#undef EPS
#undef JMAX
#undef JMAXP
#undef K
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