DTRTRI(1) LAPACK routine (version 3.2) DTRTRI(1)NAME
DTRTRI - computes the inverse of a real upper or lower triangular
matrix A
SYNOPSIS
SUBROUTINE DTRTRI( UPLO, DIAG, N, A, LDA, INFO )
CHARACTER DIAG, UPLO
INTEGER INFO, LDA, N
DOUBLE PRECISION A( LDA, * )
PURPOSE
DTRTRI computes the inverse of a real 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) 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 ref‐
erenced. If DIAG = 'U', the diagonal elements of A are also
not referenced and are assumed to be 1. On exit, the (triangu‐
lar) inverse of the original matrix, in the same storage for‐
mat.
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) November 2008 DTRTRI(1)