Provided by: liblapack-doc_3.3.1-1_all #### NAME

```       LAPACK-3 - computes the inverse of a complex upper or lower triangular matrix A

```

#### SYNOPSIS

```       SUBROUTINE CTRTRI( UPLO, DIAG, N, A, LDA, INFO )

CHARACTER      DIAG, UPLO

INTEGER        INFO, LDA, N

COMPLEX        A( LDA, * )

```

#### PURPOSE

```       CTRTRI computes the inverse of a complex upper or lower triangular matrix A.
This is the Level 3 BLAS version of the algorithm.

```

#### ARGUMENTS

```        UPLO    (input) CHARACTER*1
= 'U':  A is upper triangular;
= 'L':  A is lower triangular.

DIAG    (input) CHARACTER*1
= 'N':  A is non-unit triangular;
= 'U':  A is unit triangular.

N       (input) INTEGER
The order of the matrix A.  N >= 0.

A       (input/output) COMPLEX array, dimension (LDA,N)
On entry, the triangular matrix A.  If UPLO = 'U', the
leading N-by-N upper triangular part of the array A contains
the upper triangular matrix, and the strictly lower
triangular part of A is not referenced.  If UPLO = 'L', the
leading N-by-N lower triangular part of the array A contains
the lower triangular matrix, and the strictly upper
triangular part of A is not referenced.  If DIAG = 'U', the
diagonal elements of A are also not referenced and are
assumed to be 1.
On exit, the (triangular) inverse of the original matrix, in
the same storage format.

LDA     (input) INTEGER
The leading dimension of the array A.  LDA >= max(1,N).

INFO    (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, A(i,i) is exactly zero.  The triangular
matrix is singular and its inverse can not be computed.

LAPACK routine (version 3.2)               April 2011                            CTRTRI(3lapack)
```