d14r7.cpp

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#include<math.h>
#include<iomanip.h>
#include<iostream.h>
#include<process.h>

void rzextr(int iest,double xest,double  yest[],double yz[],double  dy[],int nv,int nuse)
{
	int j,m1,k;
    double  fx[8],yy,v,c,b1,b,ddy;
    static double x[12],d[11][ 8];
    x[iest] = xest;
    if (iest == 1)
	{
        for (j = 1; j<= nv; j++)
		{
            yz[j] = yest[j];
            d[j][1] = yest[j];
            dy[j] = yest[j];
		}
	}
    else
	{
        m1 = iest;
        if (nuse < iest) m1 = nuse;
        for( k = 1; k<= m1 - 1; k++)
		{
            fx[k + 1] = x[iest - k] / xest;
        }
        for (j = 1; j<= nv; j++)
		{
            yy = yest[j];
            v = d[j][1];
            c = yy;
            d[j][1] = yy;
            for (k = 2; k<=m1; k++)
			{
                b1 = fx[k] * v;
                b = b1 - c;
                if( b != 0.0)
				{
                    b = (c - v) / b;
                    ddy = c * b;
                    c = b1 * b;
				}
                else
				{
                    ddy = v;
                }
                if (k != m1)  v = d[j][k];
                d[j][k] = ddy;
                yy = yy + ddy;
            }
            dy[j] = ddy;
            yz[j] = yy;
		}
    }
	for (j = 1; j<=7; j++)
	{
    fx[j]=0.0;
	}
}

void main()
{
    //program d14r7
    //driver for routine rzextr
    //feed values from a rational function
    //fn(x)=(1-x+x**3)/(x+1)**n
	int nv,nuse,i,j,iest;
	double xest,dum;
    nv = 4;
    nuse = 5;
    double  yest[5],yz[5],dy[5];
    for (i = 1; i<=10; i++)
	{
        iest = i;
        xest = 1.0 / float(i);
        dum = 1.0 - xest + pow(xest ,3);
        for (j = 1; j<= nv; j++)
		{
            dum = dum / (xest + 1.0);
            yest[j] = dum;
        }
        rzextr(iest,xest,yest,yz,dy,nv,nuse);
        cout<<endl;
        cout<< setw(5)<<"Iest= "<<i;
		cout<<"      xest= "<<xest<<endl;
        cout<< setw(5)<< "Extrap. function: ";
		cout<<setprecision(6)<<setiosflags(ios::fixed);
        for (j = 1; j<= nv; j++)
		{
            cout<< setw(14)<<yz[j];
        }
		cout<<endl;
        cout<< setw(5)<< "Estimated error:  ";
        for (j = 1; j<= nv; j++)
		{
            cout<< setw(14)<<dy[j];
        }
		cout<<endl;
    }
	cout<<endl;
    cout<< setw(5)<<"actual values:    ";
	cout<< setw(14)<<"1.000000";
    cout<< setw(14)<< "1.000000"<< setw(14)<<"1.000000";
	cout<< setw(14)<< "1.000000"<<endl;
}