# cungr2.f man page

cungr2.f

## Synopsis

### Functions/Subroutines

subroutine **cungr2** (M, **N**, K, A, **LDA**, TAU, WORK, INFO)**CUNGR2** generates all or part of the unitary matrix Q from an RQ factorization determined by cgerqf (unblocked algorithm).

## Function/Subroutine Documentation

### subroutine cungr2 (integer M, integer N, integer K, complex, dimension( lda, * ) A, integer LDA, complex, dimension( * ) TAU, complex, dimension( * ) WORK, integer INFO)

**CUNGR2** generates all or part of the unitary matrix Q from an RQ factorization determined by cgerqf (unblocked algorithm).

**Purpose:**

CUNGR2 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 CGERQF.

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

*WORK*WORK is COMPLEX 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.

**Date:**December 2016

Definition at line 116 of file cungr2.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page cungr2(3) is an alias of cungr2.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK