NAME

dtrti2 - compute the inverse of a real upper or lower triangular matrix

SYNOPSIS

  SUBROUTINE DTRTI2( UPLO, DIAG, N, A, LDA, INFO)
  CHARACTER * 1 UPLO, DIAG
  INTEGER N, LDA, INFO
  DOUBLE PRECISION A(LDA,*)

  SUBROUTINE DTRTI2_64( UPLO, DIAG, N, A, LDA, INFO)
  CHARACTER * 1 UPLO, DIAG
  INTEGER*8 N, LDA, INFO
  DOUBLE PRECISION A(LDA,*)

F95 INTERFACE

  SUBROUTINE TRTI2( UPLO, DIAG, [N], A, [LDA], [INFO])
  CHARACTER(LEN=1) :: UPLO, DIAG
  INTEGER :: N, LDA, INFO
  REAL(8), DIMENSION(:,:) :: A

  SUBROUTINE TRTI2_64( UPLO, DIAG, [N], A, [LDA], [INFO])
  CHARACTER(LEN=1) :: UPLO, DIAG
  INTEGER(8) :: N, LDA, INFO
  REAL(8), DIMENSION(:,:) :: A

C INTERFACE

#include <sunperf.h>

void dtrti2(char uplo, char diag, int n, double *a, int lda, int *info);

void dtrti2_64(char uplo, char diag, long n, double *a, long lda, long *info);

PURPOSE

dtrti2 computes the inverse of a real upper or lower triangular matrix.

This is the Level 2 BLAS version of the algorithm.

ARGUMENTS

UPLO (input)
Specifies whether the matrix A is upper or lower triangular. = 'U': Upper triangular
```
 = 'L':  Lower triangular
```
DIAG (input)
Specifies whether or not the matrix A is unit triangular. = 'N': Non-unit triangular
```
 = 'U':  Unit triangular
```
N (input)
The order of the matrix A. N > = 0.
A (input/output)
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)
The leading dimension of the array A. LDA > = max(1,N).

INFO (output)

 = 0: successful exit

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