# cungr2.f man page

cungr2.f —

## Synopsis

### Functions/Subroutines

subroutinecungr2(M, N, K, A, LDA, TAU, WORK, INFO)CUNGR2generates all or part of the unitary matrix Q from an RQ factorization determined by cgerqf (unblocked algorithm).

## Function/Subroutine Documentation

### subroutine cungr2 (integerM, integerN, integerK, complex, dimension( lda, * )A, integerLDA, complex, dimension( * )TAU, complex, dimension( * )WORK, integerINFO)

**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:**

September 2012

Definition at line 115 of file cungr2.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

cungr2(3) is an alias of cungr2.f(3).