CPTTRF(l) ) CPTTRF(l)NAME
CPTTRF - compute the L*D*L' factorization of a complex Hermitian posi‐
tive definite tridiagonal matrix A
SYNOPSIS
SUBROUTINE CPTTRF( N, D, E, INFO )
INTEGER INFO, N
REAL D( * )
COMPLEX E( * )
PURPOSE
CPTTRF computes the L*D*L' factorization of a complex Hermitian posi‐
tive 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) REAL 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) COMPLEX array, dimension (N-1)
On entry, the (n-1) subdiagonal elements of the tridiagonal
matrix A. On exit, the (n-1) 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 bidiagonal
factor U from the U'*D*U factorization of A.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -k, the k-th 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 CPTTRF(l)
