DISNA: computes the reciprocal condition numbers for the eigenvectors of a real symmetric or complex Hermitian matrix or for the left or right singular vectors of a general m-by-n matrix. The reciprocal condition number is the 'gap' between the corresponding eigenvalue or singular value and the nearest other one. The bound on the error, measured by angle in radians, in the I-th computed vector is given by DLAMCH( 'E' ) * ( ANORM / SEP( I ) ) where ANORM = 2-norm(A) = max( abs( D(j) ) ). SEP(I) is not allowed to be smaller than DLAMCH( 'E' )*ANORM in order to limit the size of the error bound. DISNA may also be used to compute error bounds for eigenvectors of the generalized symmetric definite eigenproblem. More...

Public Member Functions
pure subroutine	ddisna (job, m, n, d, sep, info)

	la_ddisna

	la_qdisna

pure subroutine	sdisna (job, m, n, d, sep, info)

	la_sdisna

Detailed Description

DISNA: computes the reciprocal condition numbers for the eigenvectors of a real symmetric or complex Hermitian matrix or for the left or right singular vectors of a general m-by-n matrix. The reciprocal condition number is the 'gap' between the corresponding eigenvalue or singular value and the nearest other one. The bound on the error, measured by angle in radians, in the I-th computed vector is given by DLAMCH( 'E' ) * ( ANORM / SEP( I ) ) where ANORM = 2-norm(A) = max( abs( D(j) ) ). SEP(I) is not allowed to be smaller than DLAMCH( 'E' )*ANORM in order to limit the size of the error bound. DISNA may also be used to compute error bounds for eigenvectors of the generalized symmetric definite eigenproblem.

Member Function/Subroutine Documentation

◆ ddisna()

pure subroutine la_lapack::disna::ddisna	(	character, intent(in)	job,
		integer(ilp), intent(in)	m,
		integer(ilp), intent(in)	n,
		real(dp), dimension(*), intent(in)	d,
		real(dp), dimension(*), intent(out)	sep,
		integer(ilp), intent(out)	info
	)

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◆ la_ddisna()

la_lapack::disna::la_ddisna

◆ la_qdisna()

la_lapack::disna::la_qdisna

◆ la_sdisna()

la_lapack::disna::la_sdisna

◆ sdisna()

pure subroutine la_lapack::disna::sdisna	(	character, intent(in)	job,
		integer(ilp), intent(in)	m,
		integer(ilp), intent(in)	n,
		real(sp), dimension(*), intent(in)	d,
		real(sp), dimension(*), intent(out)	sep,
		integer(ilp), intent(out)	info
	)