g-s methom.cpp

数值分析最常用的四十种算法

int ReachTOL(double x1[],double x2[],double tol,int n)
{
	int i;
	double error=0;
	for (i=0;i<n;i++)
	{
		error+=(x1[i]-x2[i])*(x1[i]-x2[i]);
	}
	if(error<tol) 
		return 1;
	else
		return 0;
}

void GSI(double a[][N],double b[],double x0[],double tol,int max,int n)
{
	double x1[N];
	int k,i,j;
	for (i=0;i<n;i++)                     //Initialazation
	{
		x1[i]=0;
	}
	for (k=0;k<max;k++)
	{
		for (i=0;i<n;i++)
		{
			for (j=0;j<n;j++)
			{
			    if(j!=i)
				{
				    x1[i]+=a[i][j]*x0[j];
				} 
			}
		    x1[i]=((-1)*x1[i]+b[i])/a[i][i];
			if(i<n-1)
				x0[i]=x1[i];
		}
		if(ReachTOL(x0,x1,tol,n))
		{
			for (i=0;i<n;i++)
			{ 
		        x0[i]=x1[i];
			} 
			return;
		}
		x00[n-1]=x1[n-1];
		for (i=0;i<n;i++)
		{
		    x1[i]=0;
		}
	}
	for (i=0;i<n;i++)
	{ 
         x0[i]=x1[i];
	}
	return;
}