- naginterfaces.library.lapacklin.dgttrf(n, dl, d, du)[source]¶
dgttrfcomputes the factorization of a real tridiagonal matrix .
For full information please refer to the NAG Library document for f07cd
, the order of the matrix .
- dlfloat, array-like, shape
Must contain the subdiagonal elements of the matrix .
- dfloat, array-like, shape
Must contain the diagonal elements of the matrix .
- dufloat, array-like, shape
Must contain the superdiagonal elements of the matrix .
- dlfloat, ndarray, shape
Is overwritten by the multipliers that define the matrix of the factorization of .
- dfloat, ndarray, shape
Is overwritten by the diagonal elements of the upper triangular matrix from the factorization of .
- dufloat, ndarray, shape
Is overwritten by the elements of the first superdiagonal of .
- du2float, ndarray, shape
Contains the elements of the second superdiagonal of .
- ipivint, ndarray, shape
Contains the pivot indices that define the permutation matrix . At the th step, row of the matrix was interchanged with row . will always be either or , indicating that a row interchange was not performed.
- (errno )
On entry, error in parameter .
- (errno )
Element of the diagonal is exactly zero. The factorization has been completed, but the factor is exactly singular, and division by zero will occur if it is used to solve a system of equations.
dgttrfuses Gaussian elimination with partial pivoting and row interchanges to factorize the matrix as
where is a permutation matrix, is unit lower triangular with at most one nonzero subdiagonal element in each column, and is an upper triangular band matrix, with two superdiagonals.
Anderson, E, Bai, Z, Bischof, C, Blackford, S, Demmel, J, Dongarra, J J, Du Croz, J J, Greenbaum, A, Hammarling, S, McKenney, A and Sorensen, D, 1999, LAPACK Users’ Guide, (3rd Edition), SIAM, Philadelphia, https://www.netlib.org/lapack/lug