SUBROUTINE tqli(d,e,n,np,z)
      INTEGER n,np
      REAL d(np),e(np),z(np,np)
CU    USES pythag
      INTEGER i,iter,k,l,m
      REAL b,c,dd,f,g,p,r,s,pythag
      do 11 i=2,n
        e(i-1)=e(i)
11    continue
      e(n)=0.
      do 15 l=1,n
        iter=0
1       do 12 m=l,n-1
          dd=abs(d(m))+abs(d(m+1))
          if (abs(e(m))+dd.eq.dd) goto 2
12      continue
        m=n
2       if(m.ne.l)then
          if(iter.eq.30)pause 'too many iterations in tqli'
          iter=iter+1
          g=(d(l+1)-d(l))/(2.*e(l))
          r=pythag(g,1.)
          g=d(m)-d(l)+e(l)/(g+sign(r,g))
          s=1.
          c=1.
          p=0.
          do 14 i=m-1,l,-1
            f=s*e(i)
            b=c*e(i)
            r=pythag(f,g)
            e(i+1)=r
            if(r.eq.0.)then
              d(i+1)=d(i+1)-p
              e(m)=0.
              goto 1
            endif
            s=f/r
            c=g/r
            g=d(i+1)-p
            r=(d(i)-g)*s+2.*c*b
            p=s*r
            d(i+1)=g+p
            g=c*r-b
C     Omit lines from here ...
            do 13 k=1,n
              f=z(k,i+1)
              z(k,i+1)=s*z(k,i)+c*f
              z(k,i)=c*z(k,i)-s*f
13          continue
C     ... to here when finding only eigenvalues.
14        continue
          d(l)=d(l)-p
          e(l)=g
          e(m)=0.
          goto 1
        endif
15    continue
      return
      END
C  (C) Copr. 1986-92 Numerical Recipes Software .