_TRED2(3F)_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
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