sdisna()

subroutine sdisna	(	character	job,
		integer	m,
		integer	n,
		real, dimension( * )	d,
		real, dimension( * )	sep,
		integer	info )

SDISNA

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Purpose:

!>
!> SDISNA 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
!>
!>        SLAMCH( 'E' ) * ( ANORM / SEP( I ) )
!>
!> where ANORM = 2-norm(A) = max( abs( D(j) ) ).  SEP(I) is not allowed
!> to be smaller than SLAMCH( 'E' )*ANORM in order to limit the size of
!> the error bound.
!>
!> SDISNA may also be used to compute error bounds for eigenvectors of
!> the generalized symmetric definite eigenproblem.
!> 

Parameters

[in]	JOB	!> JOB is CHARACTER*1 !> Specifies for which problem the reciprocal condition numbers !> should be computed: !> = 'E': the eigenvectors of a symmetric/Hermitian matrix; !> = 'L': the left singular vectors of a general matrix; !> = 'R': the right singular vectors of a general matrix. !>
[in]	M	!> M is INTEGER !> The number of rows of the matrix. M >= 0. !>
[in]	N	!> N is INTEGER !> If JOB = 'L' or 'R', the number of columns of the matrix, !> in which case N >= 0. Ignored if JOB = 'E'. !>
[in]	D	!> D is REAL array, dimension (M) if JOB = 'E' !> dimension (min(M,N)) if JOB = 'L' or 'R' !> The eigenvalues (if JOB = 'E') or singular values (if JOB = !> 'L' or 'R') of the matrix, in either increasing or decreasing !> order. If singular values, they must be non-negative. !>
[out]	SEP	!> SEP is REAL array, dimension (M) if JOB = 'E' !> dimension (min(M,N)) if JOB = 'L' or 'R' !> The reciprocal condition numbers of the vectors. !>
[out]	INFO	!> INFO is INTEGER !> = 0: successful exit. !> < 0: if INFO = -i, the i-th argument had an illegal value. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.