STRTRI(3F) STRTRI(3F)
STRTRI - compute the inverse of a real upper or lower triangular matrix A
SUBROUTINE STRTRI( UPLO, DIAG, N, A, LDA, INFO )
CHARACTER DIAG, UPLO
INTEGER INFO, LDA, N
REAL A( LDA, * )
STRTRI computes the inverse of a real upper or lower triangular matrix A.
This is the Level 3 BLAS version of the algorithm.
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) REAL 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 = -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.
STRTRI(3F) STRTRI(3F)
STRTRI - compute the inverse of a real upper or lower triangular matrix A
SUBROUTINE STRTRI( UPLO, DIAG, N, A, LDA, INFO )
CHARACTER DIAG, UPLO
INTEGER INFO, LDA, N
REAL A( LDA, * )
STRTRI computes the inverse of a real upper or lower triangular matrix A.
This is the Level 3 BLAS version of the algorithm.
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) REAL 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 = -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.
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