dgeqpf-f(3)

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 This routine is deprecated and has been replaced by routine DGEQP3.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 M-by-N matrix A: A*P = Q*R.

Parameters:

 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 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 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 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 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 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**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).
 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

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