
DPTTRF(l) ) DPTTRF(l)
NAME
DPTTRF  compute the L*D*L' factorization of a real symmetric positive definite tridiago
nal matrix A
SYNOPSIS
SUBROUTINE DPTTRF( N, D, E, INFO )
INTEGER INFO, N
DOUBLE PRECISION D( * ), E( * )
PURPOSE
DPTTRF computes the L*D*L' factorization of a real symmetric positive definite tridiagonal
matrix A. The factorization may also be regarded as having the form A = U'*D*U.
ARGUMENTS
N (input) INTEGER
The order of the matrix A. N >= 0.
D (input/output) DOUBLE PRECISION array, dimension (N)
On entry, the n diagonal elements of the tridiagonal matrix A. On exit, the n
diagonal elements of the diagonal matrix D from the L*D*L' factorization of A.
E (input/output) DOUBLE PRECISION array, dimension (N1)
On entry, the (n1) subdiagonal elements of the tridiagonal matrix A. On exit,
the (n1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L'
factorization of A. E can also be regarded as the superdiagonal of the unit bidi
agonal factor U from the U'*D*U factorization of A.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = k, the kth argument had an illegal value
> 0: if INFO = k, the leading minor of order k is not positive definite; if k < N,
the factorization could not be completed, while if k = N, the factorization was
completed, but D(N) = 0.
LAPACK version 3.0 15 June 2000 DPTTRF(l) 
