dgecon.f3

!>
!> DGECON estimates the reciprocal of the condition number of a general
!> real matrix A, in either the 1-norm or the infinity-norm, using
!> the LU factorization computed by DGETRF.
!>
!> An estimate is obtained for norm(inv(A)), and the reciprocal of the
!> condition number is computed as
!>    RCOND = 1 / ( norm(A) * norm(inv(A)) ).
!> 

NORM

!>          NORM is CHARACTER*1
!>          Specifies whether the 1-norm condition number or the
!>          infinity-norm condition number is required:
!>          = '1' or 'O':  1-norm;
!>          = 'I':         Infinity-norm.
!> 

N

!>          N is INTEGER
!>          The order of the matrix A.  N >= 0.
!> 

A

!>          A is DOUBLE PRECISION array, dimension (LDA,N)
!>          The factors L and U from the factorization A = P*L*U
!>          as computed by DGETRF.
!> 

LDA

!>          LDA is INTEGER
!>          The leading dimension of the array A.  LDA >= max(1,N).
!> 

ANORM

!>          ANORM is DOUBLE PRECISION
!>          If NORM = '1' or 'O', the 1-norm of the original matrix A.
!>          If NORM = 'I', the infinity-norm of the original matrix A.
!> 

RCOND

!>          RCOND is DOUBLE PRECISION
!>          The reciprocal of the condition number of the matrix A,
!>          computed as RCOND = 1/(norm(A) * norm(inv(A))).
!> 

WORK

!>          WORK is DOUBLE PRECISION array, dimension (4*N)
!> 

IWORK

!>          IWORK is INTEGER array, dimension (N)
!> 

INFO

!>          INFO is INTEGER
!>          = 0:  successful exit
!>          < 0:  if INFO = -i, the i-th argument had an illegal value.
!>                NaNs are illegal values for ANORM, and they propagate to
!>                the output parameter RCOND.
!>                Infinity is illegal for ANORM, and it propagates to the output
!>                parameter RCOND as 0.
!>          = 1:  if RCOND = NaN, or
!>                   RCOND = Inf, or
!>                   the computed norm of the inverse of A is 0.
!>                In the latter, RCOND = 0 is returned.
!> 

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.