5strq.c

用C语言编写的关于矩阵特征值和特征向量的计算

  #include "math.h"
  void strq(a,n,q,b,c)
  int n;
  double a[],q[],b[],c[];
  { int i,j,k,u,v;
    double h,f,g,h2;
    for (i=0; i<=n-1; i++)
    for (j=0; j<=n-1; j++)
      { u=i*n+j; q[u]=a[u];}
    for (i=n-1; i>=1; i--)
      { h=0.0;
        if (i>1)
          for (k=0; k<=i-1; k++)
            { u=i*n+k; h=h+q[u]*q[u];}
        if (h+1.0==1.0)
          { c[i]=0.0;
            if (i==1) c[i]=q[i*n+i-1];
            b[i]=0.0;
          }
        else
          { c[i]=sqrt(h);
            u=i*n+i-1;
            if (q[u]>0.0) c[i]=-c[i];
            h=h-q[u]*c[i];
            q[u]=q[u]-c[i];
            f=0.0;
            for (j=0; j<=i-1; j++)
              { q[j*n+i]=q[i*n+j]/h;
                g=0.0;
                for (k=0; k<=j; k++)
                  g=g+q[j*n+k]*q[i*n+k];
                if (j+1<=i-1)
                  for (k=j+1; k<=i-1; k++)
                    g=g+q[k*n+j]*q[i*n+k];
                c[j]=g/h;
                f=f+g*q[j*n+i];
              }
            h2=f/(h+h);
            for (j=0; j<=i-1; j++)
              { f=q[i*n+j];
                g=c[j]-h2*f;
                c[j]=g;
                for (k=0; k<=j; k++)
                  { u=j*n+k;
                    q[u]=q[u]-f*c[k]-g*q[i*n+k];
                  }
              }
            b[i]=h;
          }
      }
    for (i=0; i<=n-2; i++) c[i]=c[i+1];
    c[n-1]=0.0;
    b[0]=0.0;
    for (i=0; i<=n-1; i++)
      { if ((b[i]!=0.0)&&(i-1>=0))
          for (j=0; j<=i-1; j++)
            { g=0.0;
              for (k=0; k<=i-1; k++)
                g=g+q[i*n+k]*q[k*n+j];
              for (k=0; k<=i-1; k++)
                { u=k*n+j;
                  q[u]=q[u]-g*q[k*n+i];
                }
            }
        u=i*n+i;
        b[i]=q[u]; q[u]=1.0;
        if (i-1>=0)
          for (j=0; j<=i-1; j++)
            { q[i*n+j]=0.0; q[j*n+i]=0.0;}
      }
    return;
  }