1CPTTRF(1)                LAPACK routine (version 3.1)                CPTTRF(1)
2
3
4

NAME

6       CPTTRF - the L*D*L' factorization of a complex Hermitian positive defi‐
7       nite tridiagonal matrix A
8

SYNOPSIS

10       SUBROUTINE CPTTRF( N, D, E, INFO )
11
12           INTEGER        INFO, N
13
14           REAL           D( * )
15
16           COMPLEX        E( * )
17

PURPOSE

19       CPTTRF computes the L*D*L' factorization of a complex  Hermitian  posi‐
20       tive  definite  tridiagonal  matrix  A.   The factorization may also be
21       regarded as having the form A = U'*D*U.
22
23

ARGUMENTS

25       N       (input) INTEGER
26               The order of the matrix A.  N >= 0.
27
28       D       (input/output) REAL array, dimension (N)
29               On entry, the n diagonal elements of the tridiagonal matrix  A.
30               On  exit, the n diagonal elements of the diagonal matrix D from
31               the L*D*L' factorization of A.
32
33       E       (input/output) COMPLEX array, dimension (N-1)
34               On entry, the (n-1) subdiagonal  elements  of  the  tridiagonal
35               matrix  A.  On exit, the (n-1) subdiagonal elements of the unit
36               bidiagonal factor L from the L*D*L' factorization of A.  E  can
37               also  be  regarded  as the superdiagonal of the unit bidiagonal
38               factor U from the U'*D*U factorization of A.
39
40       INFO    (output) INTEGER
41               = 0: successful exit
42               < 0: if INFO = -k, the k-th argument had an illegal value
43               > 0: if INFO = k, the leading minor of order k is not  positive
44               definite;  if  k < N, the factorization could not be completed,
45               while if k = N, the factorization was completed, but D(N) <= 0.
46
47
48
49 LAPACK routine (version 3.1)    November 2006                       CPTTRF(1)