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