ZLAPLL(3)

NAME
ZLAPLL - column vectors X and Y, let A = ( X Y )

SYNOPSIS

SUBROUTINE ZLAPLL(
    N, X, INCX, Y, INCY, SSMIN )

INTEGER
    INCX, INCY, N

DOUBLE
    PRECISION SSMIN

COMPLEX*16
    X( * ), Y( * )

PURPOSE
Given two column vectors X and Y, let 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.

ARGUMENTS

N       (input) INTEGER
    The length of the vectors X and Y.

X       (input/output) COMPLEX*16 array, dimension (1+(N-1)*INCX)
    On entry, X contains the N-vector X. On exit, X is overwritten.

INCX    (input) INTEGER
    The increment between successive elements of X. INCX > 0.

Y       (input/output) COMPLEX*16 array, dimension (1+(N-1)*INCY)
    On entry, Y contains the N-vector Y. On exit, Y is overwritten.

INCY    (input) INTEGER
    The increment between successive elements of Y. INCY > 0.

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