zung2l(3)

NAME

ZUNG2L - generate an m by n complex matrix Q with or

thonormal columns,

SYNOPSIS

SUBROUTINE ZUNG2L( M, N, K, A, LDA, TAU, WORK, INFO )
    INTEGER        INFO, K, LDA, M, N
    COMPLEX*16     A( LDA, * ), TAU( * ), WORK( * )

PURPOSE

ZUNG2L generates an m by n complex matrix Q with orthonor

mal 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 ZGEQLF.

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) COMPLEX*16 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 ZGEQLF in the last k columns of its ar

ray 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) COMPLEX*16 array, dimension (K)

TAU(i) must contain the scalar factor of the ele

mentary reflector H(i), as returned by ZGEQLF.

WORK (workspace) COMPLEX*16 array, dimension (N)

INFO (output) INTEGER

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

gal value

LAPACK version 3.0 15 June 2000

ZUNG2L(3)