DTRTI2(l) ) DTRTI2(l)
DTRTI2 - compute the inverse of a real upper or lower triangular matrix
SUBROUTINE DTRTI2( UPLO, DIAG, N, A, LDA, INFO )
CHARACTER DIAG, UPLO
INTEGER INFO, LDA, N
DOUBLE PRECISION A( LDA, * )
DTRTI2 computes the inverse of a real upper or lower triangular matrix. This is the Level
2 BLAS version of the algorithm.
UPLO (input) CHARACTER*1
Specifies whether the matrix A is upper or lower triangular. = 'U': Upper trian-
= 'L': Lower triangular
DIAG (input) CHARACTER*1
Specifies whether or not the matrix A is unit triangular. = 'N': Non-unit trian-
= '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 trian-
gular 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 diago-
nal 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 for-
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
LAPACK version 3.0 15 June 2000 DTRTI2(l)