---
name: "dtrtri"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/dtrtri.f"
---

# dtrtri(3)

Part of [dtrtri.f(3)](/dtrtri.f/3.md).

## NAME

SRC/dtrtri.f

## SYNOPSIS

### Functions/Subroutines

subroutine **dtrtri** (uplo, diag, n, a, lda, info)\
 **DTRTRI**

## Function/Subroutine Documentation

### subroutine dtrtri (character uplo, character diag, integer n, double precision, dimension( lda, \* ) a, integer lda, integer info)

**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.

Definition at line **108** of file **dtrtri.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.