_TRED1(3F)							    _TRED1(3F)

NAME    [Toc]    [Back]

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

SYNOPSYS    [Toc]    [Back]

	  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    [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

     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


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