雅可比迭代法和高斯赛德尔迭代法

刚学 Jacobi算法和Gauss_Siedel算法不久，觉的对以后学习会有帮助，所以记下来，希望感兴趣的朋友共勉！

#include<iostream>
#include"math.h"
using namespace std;
#define  n  3          
double a[n][n]={{5,2,1},{-1,4,2},{2,-3,10}}, x[n]={-3,2,1}, b[n]={-12,20,3}, c[n];
int i=0,j,k=0,counter=15;                                                    
int main()
{
   
    int k=0,i=0;                     
    double num1,E;        
    float y[n];
    do
    {
       E=0;     
     for(j=0;j<n;j++)
     {
       c[j]=x[j];
     }    
         num1=0;
         for(j=0;j<n;j++)
        {
            if(j!=i)
             num1=num1+a[i][j]*x[j];     
        }
        for(j=0;j<n;j++)
        {
            c[j]=x[j];
        }

        y[i]=(b[i]-num1)/a[i][i];

        if(i<n)
        {   i++; }
        
        else
        {
             for(j=0;j<n;j++)
             {  x[j]=y[j]; }
            
            for(j=0;j<n;j++)
            {
                if(E<(float)fabs(c[j]-y[j]))  E=(float)fabs(c[j]-y[j]);
            }
            if(k>=7)
            {  cout<<"Iterations is "<<k+1<<","<<"Iterative precision is  " ;
              printf("%.6lf\n",E);
              for(j=0;j<n;j++)
                printf("x[%d]=%.5lf\t",j,x[j]); 
                cout<<endl<<endl;
            }
              i=0;
              k++;
          if(E<0.001)  break;
        }     
    }while(k<=counter);
    cout<<"Iterations is "<<k<<endl;
    cout<<"Iterative terminating condition ";
    printf("x[%d]-x[%d]oo<%.6lf\n",k,k-1,E);
    cout<<"\t\t---------Solution-----------"<<endl;
    for(i=0;i<n;i++)
    {
        printf("x[%d]=%.5lf\n",i,x[i]);
    }
}

 

 

#include <iostream>
#include <math.h>
using namespace std;
int main()

{
 double a[3][3]={{1,2,-2},{3,1,-1},{2,4,1}},b[3]={10,12,-20};

double  x[3]={0,0,0},sum1,sum2;

int i,j,k,n=3;

for (k=0;k<5;k++)

{ for(i=0;i<n;i++)

    { sum1=0;sum2=0;

     for(j=0;j<i-1;j++)

      { sum1=sum1+a[i][j]*x[j];

      }

     for(j=i+1;j<n;j++)

     {sum2=sum2+a[i][j]*x[j];}

     x[i]=(b[i]-sum1-sum2)/a[i][i];

    }

   for(i=0;i<n;i++)

    { printf("x%d=%-15f",i+1,x[i]);}

     printf("\n"); 

} 

}