DLAPLL - two column vectors X and Y, let A = ( X Y )
SYNOPSIS
SUBROUTINE DLAPLL( N, X, INCX, Y, INCY, SSMIN )
INTEGER INCX, INCY, N
DOUBLE PRECISION SSMIN
DOUBLE PRECISION X( * ), Y( * )
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) INTEGER
The length of the vectors X and Y.
X (input/output) DOUBLE PRECISION 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) DOUBLE PRECISION 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 ).
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