SRC/dlapll.f(3)

NAME
SRC/dlapll.f

SYNOPSIS

  Functions/Subroutines
subroutine dlapll (n, x, incx, y, incy, ssmin)
DLAPLL measures the linear dependence of two vectors.

Function/Subroutine Documentation

  subroutine dlapll (integer n, double precision, dimension( * ) x, integer incx, double precision, dimension( * ) y, integer incy, double precision ssmin)

DLAPLL measures the linear dependence of two vectors.

Purpose:

    !>
    !> Given two column vectors X and Y, let
    !>
    !>                      A = ( X Y ).
    !>
    !> The subroutine first computes the QR factorization of A = Q*R,
    !> and then computes the SVD of the 2-by-2 upper triangular matrix R.
    !> The smaller singular value of R is returned in SSMIN, which is used
    !> as the measurement of the linear dependency of the vectors X and Y.
    !>

Parameters
    N

    !>          N is INTEGER
    !>          The length of the vectors X and Y.
    !>

    X

    !>          X is DOUBLE PRECISION array,
    !>                         dimension (1+(N-1)*INCX)
    !>          On entry, X contains the N-vector X.
    !>          On exit, X is overwritten.
    !>

    INCX

    !>          INCX is INTEGER
    !>          The increment between successive elements of X. INCX > 0.
    !>

    Y

    !>          Y is DOUBLE PRECISION array,
    !>                         dimension (1+(N-1)*INCY)
    !>          On entry, Y contains the N-vector Y.
    !>          On exit, Y is overwritten.
    !>

    INCY

    !>          INCY is INTEGER
    !>          The increment between successive elements of Y. INCY > 0.
    !>

    SSMIN

    !>          SSMIN is DOUBLE PRECISION
    !>          The smallest singular value of the N-by-2 matrix A = ( X Y ).
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 101 of file dlapll.f.

Author

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