zgerq2.f (3)  Linux Manuals
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.
NN is INTEGER The number of columns of the matrix A. N >= 0.
AA 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).
LDALDA is INTEGER The leading dimension of the array A. LDA >= max(1,M).
TAUTAU is COMPLEX*16 array, dimension (min(M,N)) The scalar factors of the elementary reflectors (see Further Details).
WORKWORK is COMPLEX*16 array, dimension (M)
INFOINFO 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
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