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



NAME
       SGECON

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



PURPOSE
            SGECON 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 SGETRF.

            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 REAL array, dimension (LDA,N)
                     The factors L and U from the factorization A = P*L*U
                     as computed by SGETRF.

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

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

           WORK      (output)
                     WORK is REAL 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                      SGECON(3)