ddisna.f3

!>
!> DDISNA 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.
!>
!> DDISNA may also be used to compute error bounds for eigenvectors of
!> the generalized symmetric definite eigenproblem.
!> 

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.
!> 

M

!>          M is INTEGER
!>          The number of rows of the matrix. M >= 0.
!> 

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'.
!> 

D

!>          D is DOUBLE PRECISION 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.
!> 

SEP

!>          SEP is DOUBLE PRECISION array, dimension (M) if JOB = 'E'
!>                               dimension (min(M,N)) if JOB = 'L' or 'R'
!>          The reciprocal condition numbers of the vectors.
!> 

INFO

!>          INFO is INTEGER
!>          = 0:  successful exit.
!>          < 0:  if INFO = -i, the i-th argument had an illegal value.
!> 

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