_TRED3(3F)							    _TRED3(3F)

NAME    [Toc]    [Back]

     TRED3, STRED3   -	EISPACK	routine.  This subroutine reduces a REAL
     SYMMETRIC matrix, stored as a one-dimensional array, to a symmetric
     tridiagonal matrix	using orthogonal similarity transformations.

SYNOPSYS    [Toc]    [Back]

	  subroutine  tred3(n, nv, a, d, e, e2)
	  integer	   n, nv
	  double precision a(nv), d(n),	e(n), e2(n)

	  subroutine stred3(n, nv, a, d, e, e2)
	  integer	   n, nv
	  real		   a(nv), d(n),	e(n), e2(n)

DESCRIPTION    [Toc]    [Back]

     On	Input n	is the order of	the matrix.

     NV	must be	set to the dimension of	the array parameter A as declared in
     the calling program dimension statement.

     A contains	the lower triangle of the real symmetric input matrix, stored
     row-wise as a one-dimensional array, in its first N*(N+1)/2 positions.
     On	Output

     A contains	information about the orthogonal transformations used in the
     reduction.

     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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