#include "math.h"
void jcbj(n,a,v,eps)
int n;
double a[],v[],eps;
{ int i,j,p,q,u,w,t,s;
double ff,fm,cn,sn,omega,x,y,d;
for (i=0; i<=n-1; i++)
{ v[i*n+i]=1.0;
for (j=0; j<=n-1; j++)
if (i!=j) v[i*n+j]=0.0;
}
ff=0.0;
for (i=1; i<=n-1; i++)
for (j=0; j<=i-1; j++)
{ d=a[i*n+j]; ff=ff+d*d; }
ff=sqrt(2.0*ff);
loop0:
ff=ff/(1.0*n);
loop1:
for (i=1; i<=n-1; i++)
for (j=0; j<=i-1; j++)
{ d=fabs(a[i*n+j]);
if (d>ff)
{ p=i; q=j;
goto loop;
}
}
if (ff<eps) return;
goto loop0;
loop: u=p*n+q; w=p*n+p; t=q*n+p; s=q*n+q;
x=-a[u]; y=(a[s]-a[w])/2.0;
omega=x/sqrt(x*x+y*y);
if (y<0.0) omega=-omega;
sn=1.0+sqrt(1.0-omega*omega);
sn=omega/sqrt(2.0*sn);
cn=sqrt(1.0-sn*sn);
fm=a[w];
a[w]=fm*cn*cn+a[s]*sn*sn+a[u]*omega;
a[s]=fm*sn*sn+a[s]*cn*cn-a[u]*omega;
a[u]=0.0; a[t]=0.0;
for (j=0; j<=n-1; j++)
if ((j!=p)&&(j!=q))
{ u=p*n+j; w=q*n+j;
fm=a[u];
a[u]=fm*cn+a[w]*sn;
a[w]=-fm*sn+a[w]*cn;
}
for (i=0; i<=n-1; i++)
if ((i!=p)&&(i!=q))
{ u=i*n+p; w=i*n+q;
fm=a[u];
a[u]=fm*cn+a[w]*sn;
a[w]=-fm*sn+a[w]*cn;
}
for (i=0; i<=n-1; i++)
{ u=i*n+p; w=i*n+q;
fm=v[u];
v[u]=fm*cn+v[w]*sn;
v[w]=-fm*sn+v[w]*cn;
}
goto loop1;
}
