qtrap.c

Numerical Recipes Software 提供的算法子程序集

#include <math.h>
#define EPS 1.0e-5
#define JMAX 20

float qtrap(func,a,b)
float (*func)(),a,b;
{
	float trapzd();
	void nrerror();
	int j;
	float s,olds;

	olds = -1.0e30;
	for (j=1;j<=JMAX;j++) {
		s=trapzd(func,a,b,j);
		if (fabs(s-olds) < EPS*fabs(olds)) return s;
		if (s == 0.0 && olds == 0.0 && j > 6) return s;
		olds=s;
	}
	nrerror("Too many steps in routine qtrap");
	return 0.0;
}
#undef EPS
#undef JMAX
/* (C) Copr. 1986-92 Numerical Recipes Software . */