DTRTI2(3F)DTRTI2(3F)NAME
DTRTI2 - compute the inverse of a real upper or lower triangular matrix
SYNOPSIS
SUBROUTINE DTRTI2( UPLO, DIAG, N, A, LDA, INFO )
CHARACTER DIAG, UPLO
INTEGER INFO, LDA, N
DOUBLE PRECISION A( LDA, * )
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) CHARACTER*1
Specifies whether the matrix A is upper or lower triangular. =
'U': Upper triangular
= 'L': Lower triangular
DIAG (input) CHARACTER*1
Specifies whether or not the matrix A is unit triangular. = 'N':
Non-unit triangular
= 'U': 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
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) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -k, the k-th argument had an illegal value
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