DLAPLL(3)      LAPACK routine of NEC Numeric Library Collection      DLAPLL(3)



NAME
       DLAPLL

SYNOPSIS
       SUBROUTINE DLAPLL (N, X, INCX, Y, INCY, SSMIN)



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.




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

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

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

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

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

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



LAPACK routine                  31 October 2017                      DLAPLL(3)