NAME

zsttrf - compute the factorization of a complex Hermitian tridiagonal matrix A

SYNOPSIS

  SUBROUTINE ZSTTRF( N, L, D, SUBL, IPIV, INFO)
  DOUBLE COMPLEX L(*), D(*), SUBL(*)
  INTEGER N, INFO
  INTEGER IPIV(*)

  SUBROUTINE ZSTTRF_64( N, L, D, SUBL, IPIV, INFO)
  DOUBLE COMPLEX L(*), D(*), SUBL(*)
  INTEGER*8 N, INFO
  INTEGER*8 IPIV(*)

F95 INTERFACE

  SUBROUTINE STTRF( [N], L, D, SUBL, IPIV, [INFO])
  COMPLEX(8), DIMENSION(:) :: L, D, SUBL
  INTEGER :: N, INFO
  INTEGER, DIMENSION(:) :: IPIV

  SUBROUTINE STTRF_64( [N], L, D, SUBL, IPIV, [INFO])
  COMPLEX(8), DIMENSION(:) :: L, D, SUBL
  INTEGER(8) :: N, INFO
  INTEGER(8), DIMENSION(:) :: IPIV

C INTERFACE

#include <sunperf.h>

void zsttrf(int n, doublecomplex *l, doublecomplex *d, doublecomplex *subl, int *ipiv, int *info);

void zsttrf_64(long n, doublecomplex *l, doublecomplex *d, doublecomplex *subl, long *ipiv, long *info);

PURPOSE

zsttrf computes the L*D*L**H factorization of a complex Hermitian tridiagonal matrix A.

ARGUMENTS

N (input)
```
 INTEGER
```
The order of the matrix A. N > = 0.
L (input/output)
```
 COMPLEX array, dimension (N)
```
On entry, the n-1 subdiagonal elements of the tridiagonal matrix A. On exit, part of the factorization of A.
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 factorization of A.
SUBL (output)
```
 COMPLEX array, dimension (N)
```
On exit, part of the factorization of A.
IPIV (output)
```
 INTEGER array, dimension (N)
```
On exit, the pivot indices of the factorization.

INFO (output)

 INTEGER

 = 0:  successful exit

 < 0:  if INFO  = -i, the i-th argument had an illegal value

 > 0:  if INFO  = i, D(k,k) is exactly zero.  The factorization has
been completed, but the block diagonal matrix D is exactly singular
and division by zero will occur if it is used to solve a system of
equations.