SRC/dpttrf.f(3)

NAME
SRC/dpttrf.f

SYNOPSIS

  Functions/Subroutines
subroutine dpttrf (n, d, e, info)
DPTTRF

Function/Subroutine Documentation

  subroutine dpttrf (integer n, double precision, dimension( * ) d, double precision, dimension( * ) e, integer info)

DPTTRF

Purpose:

    !>
    !> DPTTRF computes the L*D*L**T factorization of a real symmetric
    !> positive definite tridiagonal matrix A.  The factorization may also
    !> be regarded as having the form A = U**T*D*U.
    !>

Parameters
    N

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

    D

    !>          D is DOUBLE PRECISION array, dimension (N)
    !>          On entry, the n diagonal elements of the tridiagonal matrix
    !>          A.  On exit, the n diagonal elements of the diagonal matrix
    !>          D from the L*D*L**T factorization of A.
    !>

    E

    !>          E is DOUBLE PRECISION array, dimension (N-1)
    !>          On entry, the (n-1) subdiagonal elements of the tridiagonal
    !>          matrix A.  On exit, the (n-1) subdiagonal elements of the
    !>          unit bidiagonal factor L from the L*D*L**T factorization of A.
    !>          E can also be regarded as the superdiagonal of the unit
    !>          bidiagonal factor U from the U**T*D*U factorization of A.
    !>

    INFO

    !>          INFO is INTEGER
    !>          = 0: successful exit
    !>          < 0: if INFO = -k, the k-th argument had an illegal value
    !>          > 0: if INFO = k, the leading principal minor of order k
    !>               is not positive; if k < N, the factorization could not
    !>               be completed, while if k = N, the factorization was
    !>               completed, but D(N) <= 0.
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 90 of file dpttrf.f.

Author

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