SRC/dptcon.f(3)

NAME
SRC/dptcon.f

SYNOPSIS

  Functions/Subroutines
subroutine dptcon (n, d, e, anorm, rcond, work, info)
DPTCON

Function/Subroutine Documentation

  subroutine dptcon (integer n, double precision, dimension( * ) d, double precision, dimension( * ) e, double precision anorm, double precision rcond, double precision, dimension( * ) work, integer info)

DPTCON

Purpose:

    !>
    !> DPTCON computes the reciprocal of the condition number (in the
    !> 1-norm) of a real symmetric positive definite tridiagonal matrix
    !> using the factorization A = L*D*L**T or A = U**T*D*U computed by
    !> DPTTRF.
    !>
    !> Norm(inv(A)) is computed by a direct method, and the reciprocal of
    !> the condition number is computed as
    !>              RCOND = 1 / (ANORM * norm(inv(A))).
    !>

Parameters
    N

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

    D

    !>          D is DOUBLE PRECISION array, dimension (N)
    !>          The n diagonal elements of the diagonal matrix D from the
    !>          factorization of A, as computed by DPTTRF.
    !>

    E

    !>          E is DOUBLE PRECISION array, dimension (N-1)
    !>          The (n-1) off-diagonal elements of the unit bidiagonal factor
    !>          U or L from the factorization of A,  as computed by DPTTRF.
    !>

    ANORM

    !>          ANORM is DOUBLE PRECISION
    !>          The 1-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/(ANORM * AINVNM), where AINVNM is the
    !>          1-norm of inv(A) computed in this routine.
    !>

    WORK

    !>          WORK is DOUBLE PRECISION array, dimension (N)
    !>

    INFO

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

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Further Details:

    !>
    !>  The method used is described in Nicholas J. Higham, , SIAM J. Sci. Stat. Comput., Vol. 7, No. 1, January 1986.
    !>

Definition at line 117 of file dptcon.f.

Author

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