qsimp.c

来自「Numerical Recipes Software 提供的算法子程序集」· C语言 代码 · 共 28 行

#include <math.h>
#define EPS 1.0e-6
#define JMAX 20

float qsimp(func,a,b)
float (*func)(),a,b;
{
	float trapzd();
	void nrerror();
	int j;
	float s,st,ost,os;

	ost = os = -1.0e30;
	for (j=1;j<=JMAX;j++) {
		st=trapzd(func,a,b,j);
		s=(4.0*st-ost)/3.0;
		if (fabs(s-os) < EPS*fabs(os)) return s;
		if (s == 0.0 && os == 0.0 && j > 6) return s;
		os=s;
		ost=st;
	}
	nrerror("Too many steps in routine qsimp");
	return 0.0;
}
#undef EPS
#undef JMAX
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