TRED2(3F)

NAME
     TRED2, STRED2   -  EISPACK routine.  This subroutine reduces a REAL
     SYMMETRIC matrix to a symmetric tridiagonal matrix using and accumulating
     orthogonal similarity transformations.


SYNOPSYS
          subroutine  tred2(nm, n, a, d, e, z)
          integer          nm, n
          double precision a(nm,n), d(n), e(n), z(nm,n)

          subroutine stred2(nm, n, a, d, e, z)
          integer          nm, n
          real             a(nm,n), d(n), e(n), z(nm,n)



DESCRIPTION
     On Input

     NM must be set to the row dimension of two-dimensional array parameters
     as declared in the calling program dimension statement.

     N is the order of the matrix.

     A contains the real symmetric input matrix.  Only the lower triangle of
     the matrix need be supplied.  On Output

     D contains the diagonal elements of the tridiagonal matrix.

     E contains the subdiagonal elements of the tridiagonal matrix in its last
     N-1 positions.  E(1) is set to zero.

     Z contains the orthogonal transformation matrix produced in the
     reduction.

     A and Z may coincide.  If distinct, A is unaltered. Questions and
     comments should be directed to B. S. Garbow, APPLIED MATHEMATICS
     DIVISION, ARGONNE NATIONAL LABORATORY