Provided by: liblapack-doc_3.3.1-1_all

#### NAME

```       LAPACK-3 - computes a QR factorization of a real m by n matrix A

```

#### SYNOPSIS

```       SUBROUTINE SGEQR2P( M, N, A, LDA, TAU, WORK, INFO )

INTEGER         INFO, LDA, M, N

REAL            A( LDA, * ), TAU( * ), WORK( * )

```

#### PURPOSE

```       SGEQR2P computes a QR factorization of a real m by n matrix A:
A = Q * R.

```

#### ARGUMENTS

```        M       (input) INTEGER
The number of rows of the matrix A.  M >= 0.

N       (input) INTEGER
The number of columns of the matrix A.  N >= 0.

A       (input/output) REAL array, dimension (LDA,N)
On entry, the m by n matrix A.
On exit, the elements on and above the diagonal of the array
contain the min(m,n) by n upper trapezoidal matrix R (R is
upper triangular if m >= n); the elements below the diagonal,
with the array TAU, represent the orthogonal matrix Q as a
product of elementary reflectors (see Further Details).
LDA     (input) INTEGER
The leading dimension of the array A.  LDA >= max(1,M).

TAU     (output) REAL array, dimension (min(M,N))
The scalar factors of the elementary reflectors (see Further
Details).

WORK    (workspace) REAL array, dimension (N)

INFO    (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value

```

#### FURTHERDETAILS

```        The matrix Q is represented as a product of elementary reflectors
Q = H(1) H(2) . . . H(k), where k = min(m,n).
Each H(i) has the form
H(i) = I - tau * v * v**T
where tau is a real scalar, and v is a real vector with
v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i),
and tau in TAU(i).

LAPACK routine (version 3.3.1)             April 2011                           SGEQR2P(3lapack)
```