# DTRTI2 (3) - Linux Manuals

dtrti2.f -

## SYNOPSIS

### Functions/Subroutines

subroutine dtrti2 (UPLO, DIAG, N, A, LDA, INFO)
DTRTI2 computes the inverse of a triangular matrix (unblocked algorithm).

## Function/Subroutine Documentation

### subroutine dtrti2 (characterUPLO, characterDIAG, integerN, double precision, dimension( lda, * )A, integerLDA, integerINFO)

DTRTI2 computes the inverse of a triangular matrix (unblocked algorithm).

Purpose:

``` DTRTI2 computes the inverse of a real upper or lower triangular
matrix.

This is the Level 2 BLAS version of the algorithm.
```

Parameters:

UPLO

```          UPLO is CHARACTER*1
Specifies whether the matrix A is upper or lower triangular.
= 'U':  Upper triangular
= 'L':  Lower triangular
```

DIAG

```          DIAG is CHARACTER*1
Specifies whether or not the matrix A is unit triangular.
= 'N':  Non-unit triangular
= 'U':  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 = -k, the k-th argument had an illegal value
```

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 111 of file dtrti2.f.

## Author

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