functiondgecon

Information

Lapack documentation:

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

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

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

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

   WORK    (workspace) DOUBLE PRECISION array, dimension (4*N)

   IWORK   (workspace) INTEGER array, dimension (N)

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

   =====================================================================

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