LAPACK
3.6.1
LAPACK: Linear Algebra PACKage
|
subroutine dtbcon | ( | character | NORM, |
character | UPLO, | ||
character | DIAG, | ||
integer | N, | ||
integer | KD, | ||
double precision, dimension( ldab, * ) | AB, | ||
integer | LDAB, | ||
double precision | RCOND, | ||
double precision, dimension( * ) | WORK, | ||
integer, dimension( * ) | IWORK, | ||
integer | INFO | ||
) |
DTBCON
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DTBCON estimates the reciprocal of the condition number of a triangular band 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] | KD | KD is INTEGER The number of superdiagonals or subdiagonals of the triangular band matrix A. KD >= 0. |
[in] | AB | AB is DOUBLE PRECISION array, dimension (LDAB,N) The upper or lower triangular band matrix A, stored in the first kd+1 rows of the array. The j-th column of A is stored in the j-th column of the array AB as follows: if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j; if UPLO = 'L', AB(1+i-j,j) = A(i,j) for j<=i<=min(n,j+kd). If DIAG = 'U', the diagonal elements of A are not referenced and are assumed to be 1. |
[in] | LDAB | LDAB is INTEGER The leading dimension of the array AB. LDAB >= KD+1. |
[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 145 of file dtbcon.f.