1_2 power2.c

2． Using QR factorization to find all of the eigenvalues and eigenvectors for the following matrix

#include "stdio.h"
#include "math.h"
#define e 0.000001
main()
{   double a[3][3]={7,3,-2,3,4,-1,-2,-1,3};
    double x[3]={1,1,1},y[3]={0};
    double m=0,m1=1,max=0;
    int    i=0,j=0,k=0;
    for(k=0;k<10;k++)
    {for(i=0;i<3;i++)
     {for(j=0;j<3;j++)
      {y[i]+=a[i][j]*x[j];}
      if(fabs(y[i])>max) max=fabs(y[i]);
     }
     m=max;
     for(i=0;i<3;i++)
     {x[i]=y[i]/max;y[i]=0;}
     if(fabs((m-m1)/m)<e) break;
     m1=m;
     max=0;
    }
    for(i=0;i<3;i++)
    {printf("%f ",x[i]);}
    printf("\n%f\n",m);
    printf("times=%d",k);
    getchar();
}