DGECON(3)      LAPACK routine of NEC Numeric Library Collection      DGECON(3)



NAME
       DGECON

SYNOPSIS
       SUBROUTINE DGECON (NORM, N, A, LDA, ANORM, RCOND, WORK, IWORK, INFO)



PURPOSE
            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)) ).




ARGUMENTS
           NORM      (input)
                     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         (input)
                     N is INTEGER
                     The order of the matrix A.  N >= 0.

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

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

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

           IWORK     (output)
                     IWORK is INTEGER array, dimension (N)

           INFO      (output)
                     INFO is INTEGER
                     = 0:  successful exit
                     < 0:  if INFO = -i, the i-th argument had an illegal value



LAPACK routine                  31 October 2017                      DGECON(3)