SRC/dgecon.f(3)

NAME
SRC/dgecon.f

SYNOPSIS

  Functions/Subroutines
subroutine dgecon (norm, n, a, lda, anorm, rcond, work, iwork, info)
DGECON

Function/Subroutine Documentation

  subroutine dgecon (character norm, integer n, double precision, dimension( lda, * ) a, integer lda, double precision anorm, double precision rcond, double precision, dimension( * ) work, integer, dimension( * ) iwork, integer info)

DGECON

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)) ).

Parameters
    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.

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 130 of file dgecon.f.

Author

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