dlapll (l) - Linux Manuals

dlapll: two column vectors X and Y, let A = ( X Y )

NAME

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 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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  • dla_gerfsx_extended (l) - computes ..