# DORGR2 (3) - Linux Manuals

dorgr2.f -

## SYNOPSIS

### Functions/Subroutines

subroutine dorgr2 (M, N, K, A, LDA, TAU, WORK, INFO)
DORGR2 generates all or part of the orthogonal matrix Q from an RQ factorization determined by sgerqf (unblocked algorithm).

## Function/Subroutine Documentation

### subroutine dorgr2 (integerM, integerN, integerK, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( * )TAU, double precision, dimension( * )WORK, integerINFO)

DORGR2 generates all or part of the orthogonal matrix Q from an RQ factorization determined by sgerqf (unblocked algorithm).

Purpose:

``` DORGR2 generates an m by n real 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(2) . . . H(k)

as returned by DGERQF.
```

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 DOUBLE PRECISION 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 DGERQF 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 DOUBLE PRECISION array, dimension (K)
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by DGERQF.
```

WORK

```          WORK is DOUBLE PRECISION 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