dorg2l (l) - Linux Manuals

dorg2l: generates an m by n real matrix Q with orthonormal columns,

NAME

DORG2L - generates an m by n real matrix Q with orthonormal columns,

SYNOPSIS

SUBROUTINE DORG2L(

M, N, K, A, LDA, TAU, WORK, INFO )

    

INTEGER INFO, K, LDA, M, N

    

DOUBLE PRECISION A( LDA, * ), TAU( * ), WORK( * )

PURPOSE

DORG2L generates an m by n real matrix Q with orthonormal columns, which is defined as the last n columns of a product of k elementary reflectors of order m

Q  =  H(k) . . . H(2) H(1)
as returned by DGEQLF.

ARGUMENTS

M (input) INTEGER

The number of rows of the matrix Q. M >= 0.

N (input) INTEGER

The number of columns of the matrix Q. M >= N >= 0.

K (input) INTEGER

The number of elementary reflectors whose product defines the matrix Q. N >= K >= 0.

A (input/output) DOUBLE PRECISION array, dimension (LDA,N)

On entry, the (n-k+i)-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by DGEQLF in the last k columns of its array argument A. On exit, the m by n matrix Q.

LDA (input) INTEGER

The first dimension of the array A. LDA >= max(1,M).

TAU (input) DOUBLE PRECISION array, dimension (K)

TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DGEQLF.

WORK (workspace) DOUBLE PRECISION array, dimension (N)

INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = -i, the i-th argument has an illegal value