LAPACK  3.4.2
LAPACK: Linear Algebra PACKage
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dlapll.f File Reference

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Functions/Subroutines

subroutine dlapll (N, X, INCX, Y, INCY, SSMIN)
 DLAPLL measures the linear dependence of two vectors.

Function/Subroutine Documentation

subroutine dlapll ( integer  N,
double precision, dimension( * )  X,
integer  INCX,
double precision, dimension( * )  Y,
integer  INCY,
double precision  SSMIN 
)

DLAPLL measures the linear dependence of two vectors.

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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:
[in]N
          N is INTEGER
          The length of the vectors X and Y.
[in,out]X
          X is DOUBLE PRECISION array,
                         dimension (1+(N-1)*INCX)
          On entry, X contains the N-vector X.
          On exit, X is overwritten.
[in]INCX
          INCX is INTEGER
          The increment between successive elements of X. INCX > 0.
[in,out]Y
          Y is DOUBLE PRECISION array,
                         dimension (1+(N-1)*INCY)
          On entry, Y contains the N-vector Y.
          On exit, Y is overwritten.
[in]INCY
          INCY is INTEGER
          The increment between successive elements of Y. INCY > 0.
[out]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.
Date:
September 2012

Definition at line 103 of file dlapll.f.

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