CGEQR2 man page on Oracle

```cgeqr2.f(3)			    LAPACK			   cgeqr2.f(3)

NAME
cgeqr2.f -

SYNOPSIS
Functions/Subroutines
subroutine cgeqr2 (M, N, A, LDA, TAU, WORK, INFO)
CGEQR2 computes the QR factorization of a general rectangular
matrix using an unblocked algorithm.

Function/Subroutine Documentation
subroutine cgeqr2 (integerM, integerN, complex, dimension( lda, * )A,
integerLDA, complex, dimension( * )TAU, complex, dimension( * )WORK,
integerINFO)
CGEQR2 computes the QR factorization of a general rectangular matrix
using an unblocked algorithm.

Purpose:

CGEQR2 computes a QR factorization of a complex m by n matrix A:
A = Q * R.

Parameters:
M

M is INTEGER
The number of rows of the matrix A.  M >= 0.

N

N is INTEGER
The number of columns of the matrix A.  N >= 0.

A

A is COMPLEX 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 unitary matrix Q as a
product of elementary reflectors (see Further Details).

LDA

LDA is INTEGER
The leading dimension of the array A.  LDA >= max(1,M).

TAU

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

WORK

WORK is COMPLEX array, dimension (N)

INFO

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

Author:
Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:
September 2012

Further Details:

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**H

where tau is a complex scalar, and v is a complex 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).

Definition at line 122 of file cgeqr2.f.

Author
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2			Tue Sep 25 2012			   cgeqr2.f(3)
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