dgeqr2p.f(3) LAPACK dgeqr2p.f(3)
subroutine dgeqr2p (M, N, A, LDA, TAU, WORK, INFO)
DGEQR2P computes the QR factorization of a general rectangular matrix with non-
negative diagonal elements using an unblocked algorithm.
subroutine dgeqr2p (integerM, integerN, double precision, dimension( lda, * )A, integerLDA,
double precision, dimension( * )TAU, double precision, dimension( * )WORK, integerINFO)
DGEQR2P computes the QR factorization of a general rectangular matrix with non-negative
diagonal elements using an unblocked algorithm.
DGEQR2 computes a QR factorization of a real m by n matrix A:
A = Q * R.
M is INTEGER
The number of rows of the matrix A. M >= 0.
N is INTEGER
The number of columns of the matrix A. N >= 0.
A is DOUBLE PRECISION 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 is INTEGER
The leading dimension of the array A. LDA >= max(1,M).
TAU is DOUBLE PRECISION array, dimension (min(M,N))
The scalar factors of the elementary reflectors (see Further
WORK is DOUBLE PRECISION array, dimension (N)
INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
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).
Definition at line 122 of file dgeqr2p.f.
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Version 3.4.2 Tue Sep 25 2012 dgeqr2p.f(3)