# cunglq.f (3) - Linux Manuals

cunglq.f -

## SYNOPSIS

### Functions/Subroutines

subroutine cunglq (M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
CUNGLQ

## Function/Subroutine Documentation

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

CUNGLQ

Purpose:

``` CUNGLQ generates an M-by-N complex matrix Q with orthonormal rows,
which is defined as the first M rows of a product of K elementary
reflectors of order N

Q  =  H(k)**H . . . H(2)**H H(1)**H

as returned by CGELQF.
```

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 i-th row must contain the vector which defines
the elementary reflector H(i), for i = 1,2,...,k, as returned
by CGELQF in the first 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 CGELQF.
```

WORK

```          WORK is COMPLEX array, dimension (MAX(1,LWORK))
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
```

LWORK

```          LWORK is INTEGER
The dimension of the array WORK. LWORK >= max(1,M).
For optimum performance LWORK >= M*NB, where NB is
the optimal blocksize.

If LWORK = -1, then a workspace query is assumed; the routine
only calculates the optimal size of the WORK array, returns
this value as the first entry of the WORK array, and no error
message related to LWORK is issued by XERBLA.
```

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