/* -- translated by f2c (version 20100827).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
#include "f2c.h"
/* Table of constant values */
static integer c__1 = 1;
/* > \brief \b DORG2R generates all or part of the orthogonal matrix Q from a QR factorization determined by s
geqrf (unblocked algorithm).
=========== DOCUMENTATION ===========
Online html documentation available at
http://www.netlib.org/lapack/explore-html/
> \htmlonly
> Download DORG2R + dependencies
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f">
> [TGZ]</a>
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f">
> [ZIP]</a>
> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dorg2r.
f">
> [TXT]</a>
> \endhtmlonly
Definition:
===========
SUBROUTINE DORG2R( M, N, K, A, LDA, TAU, WORK, INFO )
INTEGER INFO, K, LDA, M, N
DOUBLE PRECISION A( LDA, * ), TAU( * ), WORK( * )
> \par Purpose:
=============
>
> \verbatim
>
> DORG2R generates an m by n real matrix Q with orthonormal columns,
> which is defined as the first n columns of a product of k elementary
> reflectors of order m
>
> Q = H(1) H(2) . . . H(k)
>
> as returned by DGEQRF.
> \endverbatim
Arguments:
==========
> \param[in] M
> \verbatim
> M is INTEGER
> The number of rows of the matrix Q. M >= 0.
> \endverbatim
>
> \param[in] N
> \verbatim
> N is INTEGER
> The number of columns of the matrix Q. M >= N >= 0.
> \endverbatim
>
> \param[in] K
> \verbatim
> K is INTEGER
> The number of elementary reflectors whose product defines the
> matrix Q. N >= K >= 0.
> \endverbatim
>
> \param[in,out] A
> \verbatim
> A is DOUBLE PRECISION array, dimension (LDA,N)
> On entry, the i-th column must contain the vector which
> defines the elementary reflector H(i), for i = 1,2,...,k, as
> returned by DGEQRF in the first k columns of its array
> argument A.
> On exit, the m-by-n matrix Q.
> \endverbatim
>
> \param[in] LDA
> \verbatim
> LDA is INTEGER
> The first dimension of the array A. LDA >= max(1,M).
> \endverbatim
>
> \param[in] TAU
> \verbatim
> TAU is DOUBLE PRECISION array, dimension (K)
> TAU(i) must contain the scalar factor of the elementary
> reflector H(i), as returned by DGEQRF.
> \endverbatim
>
> \param[out] WORK
> \verbatim
> WORK is DOUBLE PRECISION array, dimension (N)
> \endverbatim
>
> \param[out] INFO
> \verbatim
> INFO is INTEGER
> = 0: successful exit
> < 0: if INFO = -i, the i-th argument has an illegal value
> \endverbatim
Authors:
========
> \author Univ. of Tennessee
> \author Univ. of California Berkeley
> \author Univ. of Colorado Denver
> \author NAG Ltd.
> \date September 2012
> \ingroup doubleOTHERcomputational
=====================================================================
Subroutine */ int igraphdorg2r_(integer *m, integer *n, integer *k, doublereal *
a, integer *lda, doublereal *tau, doublereal *work, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2;
doublereal d__1;
/* Local variables */
integer i__, j, l;
extern /* Subroutine */ int igraphdscal_(integer *, doublereal *, doublereal *,
integer *), igraphdlarf_(char *, integer *, integer *, doublereal *,
integer *, doublereal *, doublereal *, integer *, doublereal *), igraphxerbla_(char *, integer *, ftnlen);
/* -- LAPACK computational routine (version 3.4.2) --
-- LAPACK is a software package provided by Univ. of Tennessee, --
-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
September 2012
=====================================================================
Test the input arguments
Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--tau;
--work;
/* Function Body */
*info = 0;
if (*m < 0) {
*info = -1;
} else if (*n < 0 || *n > *m) {
*info = -2;
} else if (*k < 0 || *k > *n) {
*info = -3;
} else if (*lda < max(1,*m)) {
*info = -5;
}
if (*info != 0) {
i__1 = -(*info);
igraphxerbla_("DORG2R", &i__1, (ftnlen)6);
return 0;
}
/* Quick return if possible */
if (*n <= 0) {
return 0;
}
/* Initialise columns k+1:n to columns of the unit matrix */
i__1 = *n;
for (j = *k + 1; j <= i__1; ++j) {
i__2 = *m;
for (l = 1; l <= i__2; ++l) {
a[l + j * a_dim1] = 0.;
/* L10: */
}
a[j + j * a_dim1] = 1.;
/* L20: */
}
for (i__ = *k; i__ >= 1; --i__) {
/* Apply H(i) to A(i:m,i:n) from the left */
if (i__ < *n) {
a[i__ + i__ * a_dim1] = 1.;
i__1 = *m - i__ + 1;
i__2 = *n - i__;
igraphdlarf_("Left", &i__1, &i__2, &a[i__ + i__ * a_dim1], &c__1, &tau[
i__], &a[i__ + (i__ + 1) * a_dim1], lda, &work[1]);
}
if (i__ < *m) {
i__1 = *m - i__;
d__1 = -tau[i__];
igraphdscal_(&i__1, &d__1, &a[i__ + 1 + i__ * a_dim1], &c__1);
}
a[i__ + i__ * a_dim1] = 1. - tau[i__];
/* Set A(1:i-1,i) to zero */
i__1 = i__ - 1;
for (l = 1; l <= i__1; ++l) {
a[l + i__ * a_dim1] = 0.;
/* L30: */
}
/* L40: */
}
return 0;
/* End of DORG2R */
} /* igraphdorg2r_ */