TRED1(3F)

NAME
     TRED1, STRED1   -  EISPACK routine.  This subroutine reduces a REAL
     SYMMETRIC matrix to a symmetric tridiagonal matrix using orthogonal
     similarity transformations.


SYNOPSYS
          subroutine  tred1(nm, n, a, d, e, e2)
          integer          nm, n
          double precision a(nm,n), d(n), e(n), e2(n)

          subroutine  sred1(nm, n, a, d, e, e2)
          integer          nm, n
          real             a(nm,n), d(n), e(n), e2(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

     A contains information about the orthogonal trans- formations used in the
     reduction in its strict lower triangle.  The full upper triangle of A is
     unaltered.

     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.

     E2 contains the squares of the corresponding elements of E. E2 may
     coincide with E if the squares are not needed.  Questions and comments
     should be directed to B. S. Garbow, APPLIED MATHEMATICS DIVISION, ARGONNE
     NATIONAL LABORATORY