_TRED1(3F)_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
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