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LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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| subroutine sgtcon | ( | character | NORM, |
| integer | N, | ||
| real, dimension( * ) | DL, | ||
| real, dimension( * ) | D, | ||
| real, dimension( * ) | DU, | ||
| real, dimension( * ) | DU2, | ||
| integer, dimension( * ) | IPIV, | ||
| real | ANORM, | ||
| real | RCOND, | ||
| real, dimension( * ) | WORK, | ||
| integer, dimension( * ) | IWORK, | ||
| integer | INFO | ||
| ) |
SGTCON
Download SGTCON + dependencies [TGZ] [ZIP] [TXT]
SGTCON estimates the reciprocal of the condition number of a real tridiagonal matrix A using the LU factorization as computed by SGTTRF. 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 REAL array, dimension (N-1)
The (n-1) multipliers that define the matrix L from the
LU factorization of A as computed by SGTTRF. |
| [in] | D | D is REAL array, dimension (N)
The n diagonal elements of the upper triangular matrix U from
the LU factorization of A. |
| [in] | DU | DU is REAL array, dimension (N-1)
The (n-1) elements of the first superdiagonal of U. |
| [in] | DU2 | DU2 is REAL 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 REAL array, dimension (2*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 |
1.9.4