
zgerq2.f(3) LAPACK zgerq2.f(3)
NAME
zgerq2.f 
SYNOPSIS
Functions/Subroutines
subroutine zgerq2 (M, N, A, LDA, TAU, WORK, INFO)
ZGERQ2 computes the RQ factorization of a general rectangular matrix using an
unblocked algorithm.
Function/Subroutine Documentation
subroutine zgerq2 (integerM, integerN, complex*16, dimension( lda, * )A, integerLDA,
complex*16, dimension( * )TAU, complex*16, dimension( * )WORK, integerINFO)
ZGERQ2 computes the RQ factorization of a general rectangular matrix using an unblocked
algorithm.
Purpose:
ZGERQ2 computes an RQ factorization of a complex m by n matrix A:
A = R * Q.
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*16 array, dimension (LDA,N)
On entry, the m by n matrix A.
On exit, if m <= n, the upper triangle of the subarray
A(1:m,nm+1:n) contains the m by m upper triangular matrix R;
if m >= n, the elements on and above the (mn)th subdiagonal
contain the m by n upper trapezoidal matrix R; the remaining
elements, 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*16 array, dimension (min(M,N))
The scalar factors of the elementary reflectors (see Further
Details).
WORK
WORK is COMPLEX*16 array, dimension (M)
INFO
INFO is INTEGER
= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
Further Details:
The matrix Q is represented as a product of elementary reflectors
Q = H(1)**H H(2)**H . . . H(k)**H, 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(nk+i+1:n) = 0 and v(nk+i) = 1; conjg(v(1:nk+i1)) is stored on
exit in A(mk+i,1:nk+i1), and tau in TAU(i).
Definition at line 124 of file zgerq2.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Tue Sep 25 2012 zgerq2.f(3) 
