VS2005下使用GSL-1.15小结

/*
 int gsl_integration_qng (const gsl_function * f,

                        double a, double b,

                        double epsabs, double epsrel,

                        double *result, double *abserr,

                        size_t * neval);

这个函数将用10点、21点、43点、87点的gauss-krondrod积分来计算直到误差在允许范围之内，
函数返回积分结果result、使用的积分点数neval、绝对误差值估计值abserr。a,b是积分上下限，
epsabs为绝对误差上限，epsrel为相对误差上限。

f是一个结构体，它指明要积分的表达式函数。
*/


//#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <gsl/gsl_sf_bessel.h>
#include <gsl/gsl_integration.h>

//visualsan@yahoo.cn
double fx(double x, void*params)
{
	return sin(x)/x;
}

//visualsan@yahoo.cn
double fcos(double x, void*params)
{
	return cos(x)/x;
}

//int _tmain(int argc, _TCHAR* argv[])
int main (void)
{
	printf("hello world\n");

	double x;
	x=5.0;
	double y = gsl_sf_bessel_J0(x);
	printf( "J0(%g) = %.18e\n", x, y );

	gsl_function f;
	f.function=fx;

	double r,er;
	unsigned int n;
	gsl_integration_qng(&f,1,2,1e-10,1e-10,&r,&er,&n);

	printf("result=%f\n",r);
	printf("abserr=%f\n",er);
	printf("neval=%d\n",n);

	gsl_function f_cos;
	f_cos.function=fcos;

	double cos_r,cos_er;
	unsigned int cos_n;

	printf("hello world\n");

	gsl_integration_qng(&f_cos,1,2,1e-10,1e-10,&cos_r,&cos_er,&cos_n);
	printf("cosine result=%f\n",cos_r);
	printf("cosine abserr=%f\n",cos_er);
	printf("cosine neval=%d\n",cos_n);

	printf("hello world\n");
	printf("hello world\n");

	return 0;
}

hello world
J0(5) = -1.775967713143382600e-001
result=0.659330
abserr=0.000000
neval=21
hello world
cosine result=0.085577
cosine abserr=0.000000
cosine neval=21
hello world
hello world
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