SRC/zlapll.f(3) Library Functions Manual SRC/zlapll.f(3)

SRC/zlapll.f


subroutine zlapll (n, x, incx, y, incy, ssmin)
ZLAPLL measures the linear dependence of two vectors.

ZLAPLL 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 COMPLEX*16 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 COMPLEX*16 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 99 of file zlapll.f.

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