Provided by: liblapack-doc_3.3.1-1_all

#### NAME

```       LAPACK-3  -  computes  the L*D*L**H factorization of a complex Hermitian positive definite
tridiagonal matrix A

```

#### SYNOPSIS

```       SUBROUTINE ZPTTRF( N, D, E, INFO )

INTEGER        INFO, N

DOUBLE         PRECISION D( * )

COMPLEX*16     E( * )

```

#### PURPOSE

```       ZPTTRF computes the L*D*L**H  factorization  of  a  complex  Hermitian  positive  definite
tridiagonal matrix A.  The factorization may also
be regarded as having the form A = U**H *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**H factorization of A.

E       (input/output) COMPLEX*16 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**H factorization of A.
E can also be regarded as the superdiagonal of the unit
bidiagonal factor U from the U**H *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 routine (version 3.3.1)             April 2011                            ZPTTRF(3lapack)
```