# CGEQPF (3) - Linux Man Pages

cgeqpf.f -

## SYNOPSIS

### Functions/Subroutines

subroutine cgeqpf (M, N, A, LDA, JPVT, TAU, WORK, RWORK, INFO)
CGEQPF

## Function/Subroutine Documentation

### subroutine cgeqpf (integerM, integerN, complex, dimension( lda, * )A, integerLDA, integer, dimension( * )JPVT, complex, dimension( * )TAU, complex, dimension( * )WORK, real, dimension( * )RWORK, integerINFO)

CGEQPF

Purpose:

This routine is deprecated and has been replaced by routine CGEQP3.

CGEQPF computes a QR factorization with column pivoting of a
complex M-by-N 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 COMPLEX array, dimension (LDA,N)
On entry, the M-by-N matrix A.
On exit, the upper triangle of the array contains the
min(M,N)-by-N upper triangular matrix R; the elements
below the diagonal, together with the array TAU,
represent the unitary 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 i-th column of A is permuted
to the front of A*P (a leading column); if JPVT(i) = 0,
the i-th column of A is a free column.
On exit, if JPVT(i) = k, then the i-th column of A*P
was the k-th column of A.

TAU

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

WORK

WORK is COMPLEX array, dimension (N)

RWORK

RWORK is REAL array, dimension (2*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

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**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).

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 149 of file cgeqpf.f.

## Author

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