# zungr2.f - Man Page

SRC/zungr2.f

## Synopsis

### Functions/Subroutines

subroutine **zungr2** (m, n, k, a, lda, tau, work, info)**ZUNGR2** generates all or part of the unitary matrix Q from an RQ factorization determined by cgerqf (unblocked algorithm).

## Function/Subroutine Documentation

### subroutine zungr2 (integer m, integer n, integer k, complex*16, dimension( lda, * ) a, integer lda, complex*16, dimension( * ) tau, complex*16, dimension( * ) work, integer info)

**ZUNGR2** generates all or part of the unitary matrix Q from an RQ factorization determined by cgerqf (unblocked algorithm).

**Purpose:**

ZUNGR2 generates an m by n complex matrix Q with orthonormal rows, which is defined as the last m rows of a product of k elementary reflectors of order n Q = H(1)**H H(2)**H . . . H(k)**H as returned by ZGERQF.

**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. N >= M.

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

*A*A is COMPLEX*16 array, dimension (LDA,N) On entry, the (m-k+i)-th row must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by ZGERQF in the last k rows 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 ZGERQF.

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

*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.

Definition at line **113** of file **zungr2.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page zungr2(3) is an alias of zungr2.f(3).

Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK