_TQL1(3F)							     _TQL1(3F)

NAME    [Toc]    [Back]

     TQL1, STQL1    -  EISPACK routine.	 This subroutine finds the eigenvalues
     of	a SYMMETRIC TRIDIAGONAL	matrix by the QL method.

SYNOPSYS    [Toc]    [Back]

	  subroutine  tql1(n, d, e, ierr)
	     integer	      n, ierr
	     double precision d(n), e(n)

	  subroutine stql1(n, d, e, ierr)
	     integer	      n, ierr
	     real	      d(n), e(n)

DESCRIPTION    [Toc]    [Back]

     On	Input

     N is the order of the matrix.

     D contains	the diagonal elements of the input matrix.

     E contains	the subdiagonal	elements of the	input matrix in	its last N-1
     positions.	 E(1) is arbitrary.  On	Output

     D contains	the eigenvalues	in ascending order.  If	an error exit is made,
     the eigenvalues are correct and ordered for indices 1,2,...IERR-1,	but
     may not be	the smallest eigenvalues.

     E has been	destroyed.

     IERR is set to Zero       for normal return, J	     if	the J-th
     eigenvalue	has not	been
	determined after 30 iterations.	 Calls PYTHAG(A,B) for sqrt(A**2 +
     B**2).  Questions and comments should be directed to B. S.	Garbow,
     APPLIED MATHEMATICS DIVISION, ARGONNE NATIONAL LABORATORY


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