# dtrtri.f man page

dtrtri.f —

## Synopsis

### Functions/Subroutines

subroutinedtrtri(UPLO, DIAG, N, A, LDA, INFO)DTRTRI

## Function/Subroutine Documentation

### subroutine dtrtri (characterUPLO, characterDIAG, integerN, double precision, dimension( lda, * )A, integerLDA, integerINFO)

**DTRTRI**

**Purpose:**

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

**Parameters:**

*UPLO*

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

*DIAG*

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

*N*

```
N is INTEGER
The order of the matrix A. N >= 0.
```

*A*

```
A is DOUBLE PRECISION 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*

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

*INFO*

```
INFO is 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.
```

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

November 2011

Definition at line 110 of file dtrtri.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

dtrtri(3) is an alias of dtrtri.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK