_TRED2(3F)							    _TRED2(3F)

NAME    [Toc]    [Back]

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

SYNOPSYS    [Toc]    [Back]

	  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    [Toc]    [Back]

     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


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