# zung2l.f (3) - Linux Man Pages

zung2l.f -

## 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 (integerM, integerN, integerK, complex*16, dimension( lda, * )A, integerLDA, complex*16, dimension( * )TAU, complex*16, dimension( * )WORK, integerINFO)

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