# zung2l.f - Man Page

## Synopsis

### Functions/Subroutines

subroutine **zung2l** (M, **N**, K, A, **LDA**, TAU, WORK, INFO)**ZUNG2L** generates all or part of the unitary matrix Q from a QL factorization determined by cgeqlf (unblocked algorithm).

## Function/Subroutine Documentation

### subroutine zung2l (integer M, integer N, integer K, complex*16, dimension( lda, * ) A, integer LDA, complex*16, dimension( * ) TAU, complex*16, dimension( * ) WORK, integer INFO)

**ZUNG2L** generates all or part of the unitary matrix Q from a QL factorization determined by cgeqlf (unblocked algorithm).

**Purpose:**

ZUNG2L generates an m by n complex 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 ZGEQLF.

**Parameters:***M*M is INTEGER The number of rows of the matrix Q. M >= 0.

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

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

*A*A is 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 array argument A. On exit, the m-by-n matrix Q.

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

*TAU*TAU is COMPLEX*16 array, dimension (K) TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by ZGEQLF.

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

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

**Author:**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**December 2016

Definition at line 116 of file zung2l.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page zung2l(3) is an alias of zung2l.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK