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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine cgtcon | ( | character | NORM, |
integer | N, | ||
complex, dimension( * ) | DL, | ||
complex, dimension( * ) | D, | ||
complex, dimension( * ) | DU, | ||
complex, dimension( * ) | DU2, | ||
integer, dimension( * ) | IPIV, | ||
real | ANORM, | ||
real | RCOND, | ||
complex, dimension( * ) | WORK, | ||
integer | INFO | ||
) |
CGTCON
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CGTCON estimates the reciprocal of the condition number of a complex tridiagonal matrix A using the LU factorization as computed by CGTTRF. An estimate is obtained for norm(inv(A)), and the reciprocal of the condition number is computed as RCOND = 1 / (ANORM * 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] | N | N is INTEGER The order of the matrix A. N >= 0. |
[in] | DL | DL is COMPLEX array, dimension (N-1) The (n-1) multipliers that define the matrix L from the LU factorization of A as computed by CGTTRF. |
[in] | D | D is COMPLEX array, dimension (N) The n diagonal elements of the upper triangular matrix U from the LU factorization of A. |
[in] | DU | DU is COMPLEX array, dimension (N-1) The (n-1) elements of the first superdiagonal of U. |
[in] | DU2 | DU2 is COMPLEX array, dimension (N-2) The (n-2) elements of the second superdiagonal of U. |
[in] | IPIV | IPIV is INTEGER array, dimension (N) The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required. |
[in] | ANORM | ANORM is REAL If NORM = '1' or 'O', the 1-norm of the original matrix A. If NORM = 'I', the infinity-norm of the original matrix A. |
[out] | RCOND | RCOND is REAL The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an estimate of the 1-norm of inv(A) computed in this routine. |
[out] | WORK | WORK is COMPLEX array, dimension (2*N) |
[out] | INFO | INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value |
Definition at line 143 of file cgtcon.f.