LAPACK
3.6.1
LAPACK: Linear Algebra PACKage
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subroutine dtrcon | ( | character | NORM, |
character | UPLO, | ||
character | DIAG, | ||
integer | N, | ||
double precision, dimension( lda, * ) | A, | ||
integer | LDA, | ||
double precision | RCOND, | ||
double precision, dimension( * ) | WORK, | ||
integer, dimension( * ) | IWORK, | ||
integer | INFO | ||
) |
DTRCON
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DTRCON estimates the reciprocal of the condition number of a triangular matrix A, in either the 1-norm or the infinity-norm. The norm of A is computed and an estimate is obtained for norm(inv(A)), then the reciprocal of the condition number is computed as RCOND = 1 / ( norm(A) * norm(inv(A)) ).
[in] | NORM | NORM is CHARACTER*1 Specifies whether the 1-norm condition number or the infinity-norm condition number is required: = '1' or 'O': 1-norm; = 'I': Infinity-norm. |
[in] | UPLO | UPLO is CHARACTER*1 = 'U': A is upper triangular; = 'L': A is lower triangular. |
[in] | DIAG | DIAG is CHARACTER*1 = 'N': A is non-unit triangular; = 'U': A is unit triangular. |
[in] | N | N is INTEGER The order of the matrix A. N >= 0. |
[in] | A | A is DOUBLE PRECISION array, dimension (LDA,N) 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. |
[in] | LDA | LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N). |
[out] | RCOND | RCOND is DOUBLE PRECISION The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))). |
[out] | WORK | WORK is DOUBLE PRECISION array, dimension (3*N) |
[out] | IWORK | IWORK is INTEGER array, dimension (N) |
[out] | INFO | INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value |
Definition at line 139 of file dtrcon.f.