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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