LAGTF: factorizes the matrix (T - lambda*I), where T is an n by n tridiagonal matrix and lambda is a scalar, as T - lambda*I = PLU, where P is a permutation matrix, L is a unit lower tridiagonal matrix with at most one non-zero sub-diagonal elements per column and U is an upper triangular matrix with at most two non-zero super-diagonal elements per column. The factorization is obtained by Gaussian elimination with partial pivoting and implicit row scaling. The parameter LAMBDA is included in the routine so that LAGTF may be used, in conjunction with DLAGTS, to obtain eigenvectors of T by inverse iteration. More...

Public Member Functions
pure subroutine	dlagtf (n, a, lambda, b, c, tol, d, in, info)

	la_dlagtf

	la_qlagtf

pure subroutine	slagtf (n, a, lambda, b, c, tol, d, in, info)

	la_slagtf

Detailed Description

LAGTF: factorizes the matrix (T - lambda*I), where T is an n by n tridiagonal matrix and lambda is a scalar, as T - lambda*I = PLU, where P is a permutation matrix, L is a unit lower tridiagonal matrix with at most one non-zero sub-diagonal elements per column and U is an upper triangular matrix with at most two non-zero super-diagonal elements per column. The factorization is obtained by Gaussian elimination with partial pivoting and implicit row scaling. The parameter LAMBDA is included in the routine so that LAGTF may be used, in conjunction with DLAGTS, to obtain eigenvectors of T by inverse iteration.

Member Function/Subroutine Documentation

◆ dlagtf()

pure subroutine la_lapack::lagtf::dlagtf	(	integer(ilp), intent(in)	n,
		real(dp), dimension(*), intent(inout)	a,
		real(dp), intent(in)	lambda,
		real(dp), dimension(*), intent(inout)	b,
		real(dp), dimension(*), intent(inout)	c,
		real(dp), intent(in)	tol,
		real(dp), dimension(*), intent(out)	d,
		integer(ilp), dimension(*), intent(out)	in,
		integer(ilp), intent(out)	info
	)

◆ la_dlagtf()

la_lapack::lagtf::la_dlagtf

◆ la_qlagtf()

la_lapack::lagtf::la_qlagtf

◆ la_slagtf()

la_lapack::lagtf::la_slagtf

◆ slagtf()

pure subroutine la_lapack::lagtf::slagtf	(	integer(ilp), intent(in)	n,
		real(sp), dimension(*), intent(inout)	a,
		real(sp), intent(in)	lambda,
		real(sp), dimension(*), intent(inout)	b,
		real(sp), dimension(*), intent(inout)	c,
		real(sp), intent(in)	tol,
		real(sp), dimension(*), intent(out)	d,
		integer(ilp), dimension(*), intent(out)	in,
		integer(ilp), intent(out)	info
	)

The documentation for this interface was generated from the following file:

la_lapack.f90