
dgeqpf.f(3) LAPACK dgeqpf.f(3)
NAME
dgeqpf.f 
SYNOPSIS
Functions/Subroutines
subroutine dgeqpf (M, N, A, LDA, JPVT, TAU, WORK, INFO)
DGEQPF
Function/Subroutine Documentation
subroutine dgeqpf (integerM, integerN, double precision, dimension( lda, * )A, integerLDA,
integer, dimension( * )JPVT, double precision, dimension( * )TAU, double precision,
dimension( * )WORK, integerINFO)
DGEQPF
Purpose:
This routine is deprecated and has been replaced by routine DGEQP3.
DGEQPF computes a QR factorization with column pivoting of a
real MbyN matrix A: A*P = 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 DOUBLE PRECISION array, dimension (LDA,N)
On entry, the MbyN matrix A.
On exit, the upper triangle of the array contains the
min(M,N)byN upper triangular matrix R; the elements
below the diagonal, together with the array TAU,
represent the orthogonal matrix Q as a product of
min(m,n) elementary reflectors.
LDA
LDA is INTEGER
The leading dimension of the array A. LDA >= max(1,M).
JPVT
JPVT is INTEGER array, dimension (N)
On entry, if JPVT(i) .ne. 0, the ith column of A is permuted
to the front of A*P (a leading column); if JPVT(i) = 0,
the ith column of A is a free column.
On exit, if JPVT(i) = k, then the ith column of A*P
was the kth column of A.
TAU
TAU is DOUBLE PRECISION array, dimension (min(M,N))
The scalar factors of the elementary reflectors.
WORK
WORK is DOUBLE PRECISION array, dimension (3*N)
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:
November 2011
Further Details:
The matrix Q is represented as a product of elementary reflectors
Q = H(1) H(2) . . . H(n)
Each H(i) has the form
H = I  tau * v * v**T
where tau is a real scalar, and v is a real vector with
v(1:i1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i).
The matrix P is represented in jpvt as follows: If
jpvt(j) = i
then the jth column of P is the ith canonical unit vector.
Partial column norm updating strategy modified by
Z. Drmac and Z. Bujanovic, Dept. of Mathematics,
University of Zagreb, Croatia.
 April 2011 
For more details see LAPACK Working Note 176.
Definition at line 143 of file dgeqpf.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Tue Sep 25 2012 dgeqpf.f(3) 
